1
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Karuth A, Casanola-Martin GM, Lystrom L, Sun W, Kilin D, Kilina S, Rasulev B. Combined Machine Learning, Computational, and Experimental Analysis of the Iridium(III) Complexes with Red to Near-Infrared Emission. J Phys Chem Lett 2024; 15:471-480. [PMID: 38190332 DOI: 10.1021/acs.jpclett.3c02533] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2024]
Abstract
Various coordination complexes have been the subject of experimental and theoretical studies in recent decades because of their fascinating photophysical properties. In this work, a combined experimental and computational approach was applied to investigate the optical properties of monocationic Ir(III) complexes. An interpretative machine learning-based quantitative structure-property relationship (ML/QSPR) model was successfully developed that could reliably predict the emission wavelength of the Ir(III) complexes and provide a foundation for the theoretical evaluation of the optical properties of Ir(III) complexes. A hypothesis was proposed to explain the differences in the emission wavelengths between structurally different individual Ir(III) complexes. The efficacy of the developed model was demonstrated by high R2 values of 0.84 and 0.87 for the training and test sets, respectively. It is worth noting that a relationship between the N-N distance in the diimine ligands of the Ir(III) complexes and emission wavelengths is detected. This effect is most probably associated with a degree of distortion in the octahedral geometry of the complexes, resulting in a perturbed ligand field. This combined experimental and computational approach shows great potential for the rational design of new Ir(III) complexes with the desired optical properties. Moreover, the developed methodology could be extended to other transition-metal complexes.
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Affiliation(s)
- Anas Karuth
- Coatings and Polymeric Materials, North Dakota State University, Fargo, North Dakota 58108, United States
| | - Gerardo M Casanola-Martin
- Coatings and Polymeric Materials, North Dakota State University, Fargo, North Dakota 58108, United States
| | - Levi Lystrom
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108, United States
| | - Wenfang Sun
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108, United States
- Department of Chemistry and Biochemistry, The University of Alabama, Tuscaloosa, Alabama 35487, United States
| | - Dmitri Kilin
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108, United States
| | - Svetlana Kilina
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108, United States
| | - Bakhtiyor Rasulev
- Coatings and Polymeric Materials, North Dakota State University, Fargo, North Dakota 58108, United States
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2
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Forde A, Lystrom L, Sun W, Kilin D, Kilina S. Improving Near-Infrared Emission of meso-Aryldipyrrin Indium(III) Complexes via Annulation Bridging: Excited-State Dynamics. J Phys Chem Lett 2022; 13:9210-9220. [PMID: 36170557 DOI: 10.1021/acs.jpclett.2c02115] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Using non-adiabatic dynamics and Redfield theory, we predicted the optical spectra, radiative and nonradiative decay rates, and photoluminescence quantum yields (PLQYs) for In(III) dipyrrin-based complexes (i) with electron-withdrawing (EW) or electron-donating (ED) substituents on the meso-phenyl group and (ii) upon fusing the pyrrin and phenyl rings via saturated or unsaturated bridging to increase structural rigidity. The ED groups lead to a primary π,π* character with a minor intraligand charge transfer (ILCT) contribution to the emissive state, while EW groups increase the ILCT contribution and red-shift the luminescence to ∼1.5 eV. Saturated annulation enhances the PLQYs for complexes with primary π,π* character compared to those of the non-annulated and unsaturated-annulated complexes, while both unsaturated and saturated annulation decrease the PLQYs for complexes with primary ILCT character. We found that PLQY improvement goes beyond a simple concept of structural rigidity. In contrast, the charge transfer character of excitonic states is a key parameter for engineering the NIR emission of In(III) dipyrrin complexes.
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Affiliation(s)
- Aaron Forde
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108, United States
- Materials and Nanotechnology Program, North Dakota State University, Fargo, North Dakota 58108, United States
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
- Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Levi Lystrom
- Shock and Detonation Physics, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Wenfang Sun
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108, United States
| | - Dmitri Kilin
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108, United States
| | - Svetlana Kilina
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108, United States
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3
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Liu B, Yang X, Jabed M, Kilina S, Yang Z, Sun W. Water-soluble dinuclear iridium(III) and ruthenium(II) bis-terdentate complexes: photophysics and electrochemiluminescence. Dalton Trans 2022; 51:13858-13866. [PMID: 36040117 DOI: 10.1039/d2dt02104h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The synthesis, photophysics, and electrochemiluminescence (ECL) of four water-soluble dinuclear Ir(III) and Ru(II) complexes (1-4) terminally-capped by 4'-phenyl-2,2':6',2''-terpyridine (tpy) or 1,3-di(pyrid-2-yl)-4,6-dimethylbenzene (N^C^N) ligands and linked by a 2,7-bis(2,2':6',2''-terpyridyl)fluorene with oligoether chains on C9 are reported. The impact of the tpy or N^C^N ligands and metal centers on the photophysical properties of 1-4 was assessed by spectroscopic methods including UV-vis absorption, emission, and transient absorption, and by time-dependent density functional theory (TDDFT) calculations. These complexes exhibited distinct singlet and triplet excited-state properties upon variation of the terminal-capping terdentate ligands and the metal centers. The ECL properties of complexes 1-3 with better water solubility were investigated in neutral phosphate buffer solutions (PBS) by adding tripropylamine (TPA) as a co-reactant, and the observed ECL intensity followed the descending order of 3 > 1 > 2. Complex 3 bearing the [Ru(tpy)2]2+ units displayed more pronounced ECL signals, giving its analogues great potential for further ECL study.
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Affiliation(s)
- Bingqing Liu
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND 58108-6050, USA.
| | - Xin Yang
- School of Integrated Circuit Science and Engineering, Tianjin University of Technology, Tianjin 300384, P. R. China.
| | - Mohammed Jabed
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND 58108-6050, USA.
| | - Svetlana Kilina
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND 58108-6050, USA.
| | - Zhengchun Yang
- School of Integrated Circuit Science and Engineering, Tianjin University of Technology, Tianjin 300384, P. R. China.
| | - Wenfang Sun
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND 58108-6050, USA.
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4
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Zheng Y, Han Y, Weight BM, Lin Z, Gifford BJ, Zheng M, Kilin D, Kilina S, Doorn SK, Htoon H, Tretiak S. Photochemical spin-state control of binding configuration for tailoring organic color center emission in carbon nanotubes. Nat Commun 2022; 13:4439. [PMID: 35915090 PMCID: PMC9343348 DOI: 10.1038/s41467-022-31921-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Accepted: 07/04/2022] [Indexed: 12/04/2022] Open
Abstract
Incorporating fluorescent quantum defects in the sidewalls of semiconducting single-wall carbon nanotubes (SWCNTs) through chemical reaction is an emerging route to predictably modify nanotube electronic structures and develop advanced photonic functionality. Applications such as room-temperature single-photon emission and high-contrast bio-imaging have been advanced through aryl-functionalized SWCNTs, in which the binding configurations of the aryl group define the energies of the emitting states. However, the chemistry of binding with atomic precision at the single-bond level and tunable control over the binding configurations are yet to be achieved. Here, we explore recently reported photosynthetic protocol and find that it can control chemical binding configurations of quantum defects, which are often referred to as organic color centers, through the spin multiplicity of photoexcited intermediates. Specifically, photoexcited aromatics react with SWCNT sidewalls to undergo a singlet-state pathway in the presence of dissolved oxygen, leading to ortho binding configurations of the aryl group on the nanotube. In contrast, the oxygen-free photoreaction activates previously inaccessible para configurations through a triplet-state mechanism. These experimental results are corroborated by first principles simulations. Such spin-selective photochemistry diversifies SWCNT emission tunability by controlling the morphology of the emitting sites. Chemical functionalization of the sidewalls of single-wall carbon nanotubes (SWCNTs) is an emerging route to introduce fluorescent quantum defects and tailor the emission properties. Here, authors demonstrate that spin-selective photochemistry diversifies SWCNT emission tunability by controlling the morphology of the emitting sites.
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Affiliation(s)
- Yu Zheng
- Center for Integrated Nanotechnologies, Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA.
| | - Yulun Han
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND, 58102, USA
| | - Braden M Weight
- Center for Integrated Nanotechnologies, Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA.,Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND, 58102, USA.,Department of Physics, North Dakota State University, Fargo, ND, 58102, USA.,Department of Physics and Astronomy, University of Rochester, Rochester, NY, 14627, USA
| | - Zhiwei Lin
- Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA
| | - Brendan J Gifford
- Center for Nonlinear Studies, and Theoretical Division Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - Ming Zheng
- Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA
| | - Dmitri Kilin
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND, 58102, USA
| | - Svetlana Kilina
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND, 58102, USA
| | - Stephen K Doorn
- Center for Integrated Nanotechnologies, Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - Han Htoon
- Center for Integrated Nanotechnologies, Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA.
| | - Sergei Tretiak
- Center for Integrated Nanotechnologies, Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA. .,Center for Nonlinear Studies, and Theoretical Division Los Alamos National Laboratory, Los Alamos, NM, 87545, USA.
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5
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Raulerson EK, Cadena DM, Jabed MA, Wight CD, Lee I, Wagner HR, Brewster JT, Iverson BL, Kilina S, Roberts ST. Using Spectator Ligands to Enhance Nanocrystal-to-Molecule Electron Transfer. J Phys Chem Lett 2022; 13:1416-1423. [PMID: 35119280 DOI: 10.1021/acs.jpclett.1c03825] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Semiconductor nanocrystals (NCs) have emerged as promising photocatalysts. However, NCs are often functionalized with complex ligand shells that contain not only charge acceptors but also other "spectator ligands" that control NC solubility and affinity for target reactants. Here, we show that spectator ligands are not passive observers of photoinduced charge transfer but rather play an active role in this process. We find the rate of electron transfer from quantum-confined PbS NCs to perylenediimide acceptors can be varied by over a factor of 4 simply by coordinating cinnamate ligands with distinct dipole moments to NC surfaces. Theoretical calculations indicate this rate variation stems from both ligand-induced changes in the free energy for charge transfer and electrostatic interactions that alter perylenediimide electron acceptor orientation on NC surfaces. Our work shows NC-to-molecule charge transfer can be fine-tuned through ligand shell design, giving researchers an additional handle for enhancing NC photocatalysis.
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Affiliation(s)
- Emily K Raulerson
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Danielle M Cadena
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Mohammed A Jabed
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108, United States
| | - Christopher D Wight
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Inki Lee
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Holden R Wagner
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
| | - James T Brewster
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Brent L Iverson
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Svetlana Kilina
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108, United States
| | - Sean T Roberts
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
- Center for Dynamics and Control of Materials, The University of Texas at Austin, Austin, Texas 78712, United States
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6
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Lu C, Lu T, Cui P, Kilina S, Sun W. Photophysics and reverse saturable absorption of cationic dinuclear iridium(III) complexes bearing fluorenyl-tethered 2-(quinolin-2-yl)quinoxaline ligands. Dalton Trans 2021; 50:14309-14319. [PMID: 34558585 DOI: 10.1039/d1dt02176a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The synthesis, photophysics and reverse saturable absorption of two cationic dinuclear Ir(III) complexes bearing fluorenyl-tethered 2-(quinolin-2-yl)quinoxaline (quqo) ligands are reported in this paper. The two complexes possess intense and featureless diimine ligand localized 1ILCT (intraligand charge transfer)/1π,π* absorption bands at ca. 330 and 430 nm, and a weak 1,3MLCT (metal-to-ligand charge transfer)/1,3LLCT (ligand-to-ligand charge transfer) absorption band at >500 nm. Both complexes exhibit weak dual phosphorescence at ca. 590 nm and 710 nm, which are attributed to the 3ILCT/3π,π* and 3MLCT/3LLCT states, respectively. The low-energy 3MLCT/3LLCT state also gives rise to a moderately strong triplet excited-state absorption at 490-800 nm. Because of the stronger triplet excited-state absorption than the ground-state absorption of these complexes at 532 nm, both complexes manifest a moderate reverse saturable absorption (RSA) at 532 nm for ns laser pulses. Expansion of the π-conjugation of the fluorenyl-tethered diimine ligand in Ir-1 causes a slight red-shift of the 1ILCT/1π,π* absorption bands in its UV-vis absorption spectrum and the 3MLCT/3LLCT absorption band in the transient absorption spectrum and slightly enhances the RSA at 532 nm compared to that in Ir-2. This work represents the first report on dinuclear Ir(III) complexes that exhibit RSA at 532 nm.
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Affiliation(s)
- Cuifen Lu
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND 58108-6050, USA. .,Hubei Collaborative Innovation Center for Advanced Organochemical Materials & Ministry-of-Education Key Laboratory for the Synthesis and Application of Organic Functional Molecules, Hubei University, Wuhan, 430062, P.R. China
| | - Taotao Lu
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND 58108-6050, USA.
| | - Peng Cui
- Key Laboratory of Eco-textiles, Ministry of Education, Jiangnan University, Wuxi, Jiangsu Province 214122, P. R. China.,Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND 58108-6050, USA. .,Materials and Nanotechnology Program, North Dakota State University, Fargo, ND 58108-6050, USA
| | - Svetlana Kilina
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND 58108-6050, USA.
| | - Wenfang Sun
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND 58108-6050, USA.
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7
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Lystrom L, Shukla M, Sun W, Kilina S. Extending Fluorescence of meso-Aryldipyrrin Indium(III) Complexes to Near-Infrared Regions via Electron Withdrawing or π-Expansive Aryl Substituents. J Phys Chem Lett 2021; 12:8009-8015. [PMID: 34433275 DOI: 10.1021/acs.jpclett.1c02150] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The absorption and fluorescence spectra of 14 In(III) dipyrrin-based complexes are studied using time-dependent density functional theory (TDDFT). Calculations confirm that both heteroatom substitution of oxygen (N2O2-type) by nitrogen (N4-type) in dipyrrin ligand and functionalization at the meso-position by aromatic rings with strong electron-withdrawing (EW) substituents or extended π-conjugation are efficient tools in extending the fluorescence spectra of In(III) complexes to the near-infrared (NIR) region of 750-960 nm and in red-shifting the lowest absorption band to 560-630 nm. For all complexes, the emissive singlet state has π-π* character with a small addition of intraligand charge transfer (ILCT) contributing from the meso-aryl substituents to the dipyrrin ligand. Stronger EW nitro group on the meso-phenyl or meso-aryl group with extended π-conjugation induces red-shifted electronic absorption and fluorescence. More tetrahedral geometry of the complexes with N4-type ligands leads to less intensive but more red-shifted fluorescence to NIR, compared to the corresponding complexes with N2O2-type ligands that have a more planar geometry.
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Affiliation(s)
- Levi Lystrom
- Environmental Laboratory, U.S. Army Engineer Research and Development Center, Vicksburg, Mississippi 39180, United States
- Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee 37830, United States
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108, United States
| | - Manoj Shukla
- Environmental Laboratory, U.S. Army Engineer Research and Development Center, Vicksburg, Mississippi 39180, United States
| | - Wenfang Sun
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108, United States
| | - Svetlana Kilina
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108, United States
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8
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Weight BM, Sifain AE, Gifford BJ, Kilin D, Kilina S, Tretiak S. Coupling between Emissive Defects on Carbon Nanotubes: Modeling Insights. J Phys Chem Lett 2021; 12:7846-7853. [PMID: 34380317 DOI: 10.1021/acs.jpclett.1c01631] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Covalent functionalization of single-walled carbon nanotubes (SWCNTs) with organic molecules results in red-shifted emissive states associated with sp3-defects in the tube lattice, which facilitate their improved optical functionality, including single-photon emission. The energy of the defect-based electronic excitations (excitons) depends on the molecular adducts, the configuration of the defect, and concentration of defects. Here we model the interactions between two sp3-defects placed at various distances in the (6,5) SWCNT using time-dependent density functional theory. Calculations reveal that these interactions conform to the effective model of J-aggregates for well-spaced defects (>2 nm), leading to a red-shifted and optically allowed (bright) lowest energy exciton. H-aggregate behavior is not observed for any defect orientations, which is beneficial for emission. The splitting between the lowest energy bright and optically forbidden (dark) excitons and the pristine excitonic band are controlled by the single-defect configurations and their axial separation. These findings enable a synthetic design strategy for SWCNTs with tunable near-infrared emission.
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Affiliation(s)
- Braden M Weight
- Center for Integrated Nanotechnologies, Center for Nonlinear Studies, and Theoretical Division Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
- Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627, United States
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58102, United States
- Department of Physics, North Dakota State University, Fargo, North Dakota 58102, United States
| | - Andrew E Sifain
- U.S. Army Research Laboratory, Aberdeen Proving Ground, Maryland 21005, United States
| | - Brendan J Gifford
- Center for Integrated Nanotechnologies, Center for Nonlinear Studies, and Theoretical Division Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Dmitri Kilin
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58102, United States
| | - Svetlana Kilina
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58102, United States
| | - Sergei Tretiak
- Center for Integrated Nanotechnologies, Center for Nonlinear Studies, and Theoretical Division Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
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9
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Zhu X, Liu B, Cui P, Kilina S, Sun W. Multinuclear 2-(Quinolin-2-yl)quinoxaline-Coordinated Iridium(III) Complexes Tethered by Carbazole Derivatives: Synthesis and Photophysics. Inorg Chem 2020; 59:17096-17108. [PMID: 33170657 DOI: 10.1021/acs.inorgchem.0c02366] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Five mono/di/trinuclear iridium(III) complexes (1-5) bearing the carbazole-derivative-tethered 2-(quinolin-2-yl)quinoxaline (quqo) diimine (N^N) ligand were synthesized and characterized. The photophysical properties of these complexes and their corresponding diimine ligands were systematically studied via UV-vis absorption, emission, and transient absorption (TA) spectroscopy and simulated by time-dependent density functional theory. All complexes possessed strong well-resolved absorption bands at <400 nm that have predominant ligand-based 1π,π* transitions and broad structureless charge-transfer (1CT) absorption bands at 400-700 nm. The energies or intensities of these 1CT bands varied pronouncedly when the number of tethered Ir(quqo)(piq)2+ (piq refers to 1-phenylisoquinoline) units, π conjugation of the carbazole derivative linker, or attachment positions on the carbazole linker were altered. All complexes were emissive at room temperature, with 1-3 showing near-IR (NIR) 3MLCT (metal-to-ligand charge-transfer)/3LLCT (ligand-to-ligand charge-transfer) emission at ∼710 nm and 4 and 5 exhibiting red or NIR 3ILCT (intraligand charge-transfer)/3LMCT (ligand-to-metal charge-transfer) emission in CH2Cl2. In CH3CN, 1-3 displayed an additional emission band at ca. 590 nm (3ILCT/3LMCT/3MLCT/3π,π* in nature) in addition to the 710 nm band. The different natures of the emitting states of 1-3 versus those of 4 and 5 also gave rise to different spectral features in their triplet TA spectra. It appears that the parentage and characteristics of the lowest triplet excited states in these complexes are mainly impacted by the π systems of the bridging carbazole derivatives and essentially no interactions among the Ir(quqo)(piq)2+ units. In addition, all of the diimine ligands tethered by the carbazole derivatives displayed a dramatic solvatochromic effect in their emission due to the predominant intramolecular charge-transfer nature of their emitting states. Aggregation-enhanced emission was also observed from the mixed CH2Cl2/ethyl acetate or CH2Cl2/hexane solutions of these ligands.
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Affiliation(s)
- Xiaolin Zhu
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108-6050, United States
| | - Bingqing Liu
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108-6050, United States
| | - Peng Cui
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108-6050, United States.,Materials and Nanotechnology Program, North Dakota State University, Fargo, North Dakota 58108-6050, United States.,Key Laboratory of Eco-textiles, Ministry of Education, Jiangnan University, Wuxi, Jiangsu Province 214122, P. R. China
| | - Svetlana Kilina
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108-6050, United States
| | - Wenfang Sun
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108-6050, United States
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10
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Jabed MA, Dandu N, Tretiak S, Kilina S. Passivating Nucleobases Bring Charge Transfer Character to Optically Active Transitions in Small Silver Nanoclusters. J Phys Chem A 2020; 124:8931-8942. [PMID: 33079551 DOI: 10.1021/acs.jpca.0c06974] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
DNA-wrapped silver nanoclusters (DNA-AgNCs) are known for their efficient luminescence. However, their emission is highly sensitive to the DNA sequence, the cluster size, and its charge state. To get better insights into photophysics of these hybrid systems, simulations based on density functional theory (DFT) are performed. Our calculations elucidate the effect of the structural conformations, charges, solvent polarity, and passivating bases on optical spectra of DNA-AgNCs containing five and six Ag atoms. It is found that inclusion of water in calculations as a polar solvent media results in stabilization of nonplanar conformations of base-passivated clusters, while their planar conformations are more stable in vacuum, similar to the bare Ag5 and Ag6 clusters. Cytosines and guanines interact with the cluster twice stronger than thymines, due to their larger dipole moments. In addition to the base-cluster interactions, hydrogen bonds between bases notably contribute to the structure stabilization. While the relative intensity, line width, and the energy of absorption peaks are slightly changing depending on the cluster charge, conformations, and base types, the overall spectral shape with five well-resolved bands at 2.5-5.5 eV is consistent for all structures. Independent of the passivating bases and the cluster size and charge, the low energy optical transitions at 2.5-3.5 eV exhibit a metal to ligand charge transfer (MLCT) character with the main contribution emerging from Ag-core to the bases. Cytosines facilitate the MLCT character to a larger degree comparing to the other bases. However, the doublet transitions in clusters with the open shell electronic structure (Ag5 and Ag6+) result in appearance of additional red-shifted (<2.5 eV) and optically weak band with negligible MLCT character. The passivated clusters with the closed shell electronic structure (Ag5+ and Ag6) exhibit higher optical intensity of their lowest transitions with much higher MLCT contribution, thus having better potential for emission, than their open shell counterparts.
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Affiliation(s)
- Mohammed A Jabed
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108, United States
| | - Naveen Dandu
- Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Sergei Tretiak
- Center for Nonlinear Studies, Center for Integrated Nanotechnologies, and Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Svetlana Kilina
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108, United States
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11
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Gifford BJ, Kilina S, Htoon H, Doorn SK, Tretiak S. Controlling Defect-State Photophysics in Covalently Functionalized Single-Walled Carbon Nanotubes. Acc Chem Res 2020; 53:1791-1801. [PMID: 32805109 DOI: 10.1021/acs.accounts.0c00210] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
ConspectusSingle-walled carbon nanotubes (SWCNTs) show promise as light sources for modern fiber optical communications due to their emission wavelengths tunable via chirality and diameter dependency. However, the emission quantum yields are relatively low owing to the existence of low-lying dark electronic states and fast excitonic diffusion leading to carrier quenching at defects. Covalent functionalization of SWCNTs addresses this problem by brightening their infrared emission. Namely, introduction of sp3-hybridized defects makes the lowest energy transitions optically active for some defect geometries and enables further control of their optical properties. Such functionalized SWCNTs are currently the only material exhibiting room-temperature single photon emission at telecom relevant infrared wavelengths. While this fluorescence is strong and has the right wavelength, functionalization introduces a variety of emission peaks resulting in spectrally broad inhomogeneous photoluminescence that prohibits the use of SWCNTs in practical applications. Consequently, there is a strong need to control the emission diversity in order to render these materials useful for applications. Recent experimental and computational work has attributed the emissive diversity to the presence of multiple localized defect geometries each resulting in distinct emission energy. This Account outlines methods by which the morphology of the defect in functionalized SWCNTs can be controlled to reduce emissive diversity and to tune the fluorescence wavelengths. The chirality-dependent trends of emission energies with respect to individual defect morphologies are explored. It is demonstrated that defect geometries originating from functionalization of SWCNT carbon atoms along bonds with strong π-orbital mismatch are favorable. Furthermore, the effect of controlling the defect itself through use of different chemical groups is also discussed. Such tunability is enabled due to the formation of specific defect geometries in close proximity to other existing defects. This takes advantage of the changes in π-orbital mismatch enforced by existing defects and the resulting changes in reactivities toward formation of specific defect morphologies. Furthermore, the trends in emissive energies are highly dependent on the value of mod(n-m,3) for an (n,m) tube chirality. These powerful concepts allow for a targeted formation of defects that emit at desired energies based on SWCNT single chirality enriched samples. Finally, the impact of functionalization with specific types of defects that enforce certain defect geometries due to steric constraints in bond lengths and angles to the SWCNT are discussed. We further relate to a similar effect that is present in systems where high density of surface defects is formed due to high reactant concentration. The outlined strategies suggested by simulations are instrumental in guiding experimental efforts toward the generation of functionalized SWCNTs with tunable emission energies.
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Affiliation(s)
| | - Svetlana Kilina
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108, United States
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Li H, Liu S, Lystrom L, Kilina S, Sun W. Improving triplet excited-state absorption and lifetime of cationic iridium(III) complexes by extending π-conjugation of the 2-(2-quinolinyl)quinoxaline ligand. J Photochem Photobiol A Chem 2020. [DOI: 10.1016/j.jphotochem.2020.112609] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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White DL, Lystrom L, He X, Burkert SC, Kilin DS, Kilina S, Star A. Synthesis of Holey Graphene Nanoparticle Compounds. ACS Appl Mater Interfaces 2020; 12:36513-36522. [PMID: 32672929 DOI: 10.1021/acsami.0c09394] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Bulk-scale syntheses of sp2 nanocarbon have typically been generated by extensive chemical oxidation to yield graphite oxide from graphite, followed by a reductive step. Materials generated via harsh random processes lose desirable physical characteristics. Loss of sp2 conjugation inhibits long-range electronic transport and the potential for electronic band manipulation. Here, we present a nanopatterned holey graphene material electronically hybridized with metal-containing nanoparticles. Oxidative plasma etching of highly ordered pyrolytic graphite via previously developed covalent organic framework (COF)-5-templated patterning yields bulk-scale materials for electrocatalytic applications and fundamental investigations into band structure engineering of nanocomposites. We establish a broad ability (Ag, Au, Cu, and Ni) to grow metal-containing nanoparticles in patterned holes in a metal precursor-dependent manner without a reducing agent. Graphene nanoparticle compounds (GNCs) show metal-contingent changes in the valence band structure. Density functional theory investigations reveal preferences for uncharged metal states, metal contributions to the valence band, and embedding of nanoparticles over surface incorporation. Ni-GNCs show activity for oxygen evolution reaction in alkaline media (1 M KOH). Electrocatalytic activity exceeds 10,000 mA/mg of Ni, shows stability for 2 h of continuous operation, and is kinetically consistent via a Tafel slope with Ni(OH)2-based catalysis.
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Affiliation(s)
- David L White
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Levi Lystrom
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58102, United States
| | - Xiaoyun He
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Seth C Burkert
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Dmitri S Kilin
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58102, United States
| | - Svetlana Kilina
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58102, United States
| | - Alexander Star
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, United States
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Liu B, Gao Y, Jabed MA, Kilina S, Liu G, Sun W. Lysosome Targeting Bis-terpyridine Ruthenium(II) Complexes: Photophysical Properties and In Vitro Photodynamic Therapy. ACS Appl Bio Mater 2020; 3:6025-6038. [DOI: 10.1021/acsabm.0c00647] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Affiliation(s)
- Bingqing Liu
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108-6050, United States
| | - Yibo Gao
- State Key Laboratory of Natural and Biomimetic Drugs, School of Pharmaceutical Sciences, Peking University, Beijing 100191, P. R. China
| | - Mohammed A. Jabed
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108-6050, United States
| | - Svetlana Kilina
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108-6050, United States
| | - Guoquan Liu
- State Key Laboratory of Natural and Biomimetic Drugs, School of Pharmaceutical Sciences, Peking University, Beijing 100191, P. R. China
| | - Wenfang Sun
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108-6050, United States
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Liu B, Jabed MA, Kilina S, Sun W. Synthesis, Photophysics, and Reverse Saturable Absorption of trans-Bis-cyclometalated Iridium(III) Complexes (C^N^C)Ir(R-tpy) + (tpy = 2,2':6',2″-Terpyridine) with Broadband Excited-State Absorption. Inorg Chem 2020; 59:8532-8542. [PMID: 32497429 DOI: 10.1021/acs.inorgchem.0c00961] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Extending the bandwidth of triplet excited-state absorption in transition-metal complexes is appealing for developing broadband reverse saturable absorbers. Targeting this goal, five bis-terdentate iridium(III) complexes (Ir1-Ir5) bearing trans-bis-cyclometalating (C^N^C) and 4'-R-2,2':6',2″-terpyridine (4'-R-tpy) ligands were synthesized. The effects of the structural variation in cyclometalating ligands and substituents at the tpy ligand on the photophysics of these complexes have been systematically explored using spectroscopic methods (i.e., UV-vis absorption, emission, and transient absorption spectroscopy) and time-dependent density functional theory (TDDFT) calculations. All complexes exhibited intensely structured 1π,π* absorption bands at <400 nm and broad charge transfer (1CT)/1π,π* transitions at 400-600 nm. Ligand structural variations exerted a very small effect on the energies of the 1CT/1π,π* transitions; however, they had a significant effect on the molar extinction coefficients of these absorption bands. All complexes emitted featureless deep red phosphorescence in solutions at room temperature and gave broad-band and strong triplet excited-state absorption ranging from the visible to the near-infrared (NIR) spectral regions, with both originating from the 3π,π*/3CT states. Although alteration of the ligand structures influenced the emission energies slightly, these changes significantly affected the emission lifetimes and quantum yields, transient absorption spectral features, and the triplet excited-state quantum yields of the complexes. Except for Ir3, the other four complexes all manifested reverse saturable absorption (RSA) upon nanosecond laser pulse excitation at 532 nm, with the decreasing trend of RSA following Ir2 ≈ Ir4 > Ir1 > Ir5 > Ir3. The RSA trend corresponded well with the strength of the excited-state and ground-state absorption differences (ΔOD) at 532 nm for these complexes.
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Affiliation(s)
- Bingqing Liu
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota58108-6050, United States
| | - Mohammed A Jabed
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota58108-6050, United States
| | - Svetlana Kilina
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota58108-6050, United States
| | - Wenfang Sun
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota58108-6050, United States
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Abstract
We study the impact of the chemical composition on phonon-mediated exciton relaxation in the core/shell quantum dots (QDs), with 1 nm core made of PbX and the monolayer shell made of CdX, where X = S and Se. For this, time-domain nonadiabatic molecular dynamics (NAMD) based on density functional theory (DFT) and surface hopping techniques are applied. Simulations reveal twice faster energy relaxation in PbS/CdS than PbSe/CdSe because of dominant couplings to higher-energy optical phonons in structures with sulfur anions. For both QDs, the long-living intermediate states associated with the core-shell interface govern the dynamics. Therefore, a simple exponential model is not appropriate, and the four-state irreversible kinetic model is suggested instead, predicting 0.9 and 0.5 ps relaxation rates in PbSe/CdSe and PbS/CdS QDs, respectively. Thus, 2 nm PdSe/CdSe QDs with a single monolayer shell exhibit the phonon-mediated relaxation time sufficient for carrier multiplications to outpace energy dissipation and benefit the solar conversion efficiency.
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Affiliation(s)
- Levi Lystrom
- Chemistry & Biochemistry Department, North Dakota State University, Fargo, North Dakota 58108, United States
| | - Patrick Tamukong
- School of Medicine & Health Sciences, University of North Dakota, Grand Forks, North Dakota 58202, United States
| | - Deyan Mihaylov
- Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623, United States
| | - Svetlana Kilina
- Chemistry & Biochemistry Department, North Dakota State University, Fargo, North Dakota 58108, United States
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Wang L, Cui P, Lystrom L, Lu J, Kilina S, Sun W. Heteroleptic cationic iridium( iii) complexes bearing phenanthroline derivatives with extended π-conjugation as potential broadband reverse saturable absorbers. NEW J CHEM 2020. [DOI: 10.1039/c9nj03877a] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Fluorenyl substitution at the diimine ligand broadened the excited-state absorption to near-IR, and enhanced reverse saturable absorption at 532 nm for the cationic Ir(iii) complexes.
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Affiliation(s)
- Li Wang
- Department of Chemistry and Biochemistry
- North Dakota State University
- Fargo
- USA
| | - Peng Cui
- Department of Chemistry and Biochemistry
- North Dakota State University
- Fargo
- USA
- Materials and Nanotechnology Program
| | - Levi Lystrom
- Department of Chemistry and Biochemistry
- North Dakota State University
- Fargo
- USA
| | - Jiapeng Lu
- Department of Chemistry and Biochemistry
- North Dakota State University
- Fargo
- USA
| | - Svetlana Kilina
- Department of Chemistry and Biochemistry
- North Dakota State University
- Fargo
- USA
| | - Wenfang Sun
- Department of Chemistry and Biochemistry
- North Dakota State University
- Fargo
- USA
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Gifford BJ, Saha A, Weight BM, He X, Ao G, Zheng M, Htoon H, Kilina S, Doorn SK, Tretiak S. Mod(n-m,3) Dependence of Defect-State Emission Bands in Aryl-Functionalized Carbon Nanotubes. Nano Lett 2019; 19:8503-8509. [PMID: 31682455 DOI: 10.1021/acs.nanolett.9b02926] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Molecularly functionalized single-walled carbon nanotubes (SWCNTs) are potentially useful for fiber optical applications due to their room temperature single-photon emission capacity at telecommunication wavelengths. Several distinct defect geometries are generated upon covalent functionalization. While it has been shown that the defect geometry controls electron localization around the defect site, thereby changing the electronic structure and generating new optically bright red-shifted emission bands, the reasons for such localization remain unexplained. Our joint experimental and computational studies of functionalized SWCNTs with various chiralities show that the value of mod(n-m,3) in an (n,m) chiral nanotube plays a key role in the relative ordering of defect-dependent emission energies. This dependence is linked to the complex nodal characteristics of electronic wave function extending along specific bonds in the tube, which justifies the defect-geometry dependent exciton localization. This insight helps to uncover the essential structural motifs allowing tuning the redshifts of emission energies in functionalized SWCNTs.
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Affiliation(s)
| | - Avishek Saha
- CSIR-Central Scientific Instruments Organization , Chandigarh 160030 , India
| | | | | | - Geyou Ao
- Materials Science and Engineering Division , National Institute of Standards and Technology , Gaithersburg , Maryland 20899-8540 , United States
| | - Ming Zheng
- Materials Science and Engineering Division , National Institute of Standards and Technology , Gaithersburg , Maryland 20899-8540 , United States
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Liu B, Jabed MA, Guo J, Xu W, Brown SL, Ugrinov A, Hobbie EK, Kilina S, Qin A, Sun W. Neutral Cyclometalated Iridium(III) Complexes Bearing Substituted N-Heterocyclic Carbene (NHC) Ligands for High-Performance Yellow OLED Application. Inorg Chem 2019; 58:14377-14388. [DOI: 10.1021/acs.inorgchem.9b01678] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Bingqing Liu
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108-6050, United States
| | - Mohammed A. Jabed
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108-6050, United States
| | - Jiali Guo
- School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, People’s Republic of China
| | - Wan Xu
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108-6050, United States
- Engineering Research Center for Nanomaterials, Henan University, Kaifeng 475004, People’s Republic of China
| | - Samuel L. Brown
- Materials and Nanotechnology Program, North Dakota State University, Fargo, North Dakota 58108-6050, United States
| | - Angel Ugrinov
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108-6050, United States
| | - Erik K. Hobbie
- Materials and Nanotechnology Program, North Dakota State University, Fargo, North Dakota 58108-6050, United States
| | - Svetlana Kilina
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108-6050, United States
| | - Anjun Qin
- School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, People’s Republic of China
| | - Wenfang Sun
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108-6050, United States
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Liu B, Monro S, Jabed MA, Cameron CG, Colón KL, Xu W, Kilina S, McFarland SA, Sun W. Neutral iridium(iii) complexes bearing BODIPY-substituted N-heterocyclic carbene (NHC) ligands: synthesis, photophysics, in vitro theranostic photodynamic therapy, and antimicrobial activity. Photochem Photobiol Sci 2019; 18:2381-2396. [PMID: 31432864 PMCID: PMC6785369 DOI: 10.1039/c9pp00142e] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2019] [Accepted: 08/08/2019] [Indexed: 12/29/2022]
Abstract
The synthesis, photophysics, and photobiological activities of a series of novel neutral heteroleptic cyclometalated iridium(iii) complexes incorporating boron dipyrromethene (BODIPY) substituted N-heterocyclic carbene (NHC) ligands (Ir1-Ir5) are reported. The effect of the substitution position of BODIPY on the NHC ligands, either on C4 of the phenyl ring (Ir1-Ir3) or C5 of the benzimidazole unit (Ir4 and Ir5), and its linker type (single or triple bond) on the photophysical properties was studied. Ir1-Ir5 exhibited BODIPY-localized intense 1IL (intraligand transition)/1MLCT (metal-to-ligand charge transfer) absorption at 530-543 nm and 1,3IL/1,3CT (charge transfer) emission at 582-610 nm. The nanosecond transient absorption results revealed that the lowest triplet excited states of these complexes were the BODIPY-localized 3π,π* states. Complexes Ir4 and Ir5 exhibited blue-shifted 1IL absorption and 1,3IL/1,3CT emission bands compared to the corresponding absorption and emission bands in complexes Ir1 and Ir3. However, replacing the methyl substituents on N3 of benzimidazole in complexes Ir1 and Ir4 with oligoether substituents in Ir3 and Ir5, respectively, did not impact the energies of the low-energy absorption and emission bands in the corresponding complexes. Water-soluble complexes Ir3 and Ir5 have been explored as photosensitizers for in vitro photodynamic therapy (PDT) effects toward human SKMEL28 melanoma cells. Ir3 showed no dark cytotoxicity (EC50 > 300 μM) but good photocytotoxic activity (9.66 ± 0.28 μM), whereas Ir5 exhibited a higher dark cytotoxicity (20.2 ± 1.26 μM) and excellent photocytotoxicity (0.15 ± 0.01 μM). The phototherapeutic indices with visible light (400-700 nm) activation were >31 for Ir3 and 135 for Ir5. Ir3 and Ir5 displayed 1O2 quantum yields of 38% and 22% in CH3CN, respectively, upon 450 nm excitation. Ir5 was more effective at generating reactive oxygen species (ROS) in vitro. Ir5 was also active against Staphylococcus aureus upon visible light activation, with a phototherapeutic index of >15 and EC50 value of 6.67 μM. These photobiological activities demonstrated that these neutral Ir(iii) complexes are promising in vitro PDT reagents, and substitution at C5 on the benzimidazole group of the NHC ligand was superior to C4 substitution on the phenyl ring.
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Affiliation(s)
- Bingqing Liu
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND 58108-6050, USA.
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Liu B, Monro S, Li Z, Jabed MA, Ramirez D, Cameron CG, Colón K, Roque J, Kilina S, Tian J, McFarland SA, Sun W. A New Class of Homoleptic and Heteroleptic Bis(terpyridine) Iridium(III) Complexes with Strong Photodynamic Therapy Effects. ACS Appl Bio Mater 2019; 2:2964-2977. [PMID: 31844844 PMCID: PMC6913535 DOI: 10.1021/acsabm.9b00312] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Six homo- or heteroleptic tricationic Ir(R1-tpy)(R2-tpy)3+ complexes (Ir1-Ir6, R1/R2 = Ph, 4'-N(CH3)2Ph, pyren-1-yl, or 4'-{2-[2-(2-methoxyethoxy)ethoxy]ethoxy}Ph, tpy = 2,2';6',2"-terpyridine) were synthesized and tested for photodynamic therapy (PDT) effects. The ground- and excited-state characteristics of these complexes were studied systematically via spectroscopic methods and quantum chemistry calculations. All complexes possessed intraligand charge transfer (1ILCT) / metal-to-ligand charge transfer (1MLCT) dominated transition(s) in their low-energy absorption bands, which red-shifted with the increased electron-releasing strength of the R1/R2 substituent. Five of the complexes exhibited ligand-centered 3 π,π*/3ILCT/3MLCT emission. With a stronger electron-releasing R1/R2 substituent, the degree of charge transfer contribution increased, leading to a decrease of the emission quantum yield. When the 4'-N(CH3)2Ph substituent was introduced on both tpy ligands, the emission of Ir3 was completely quenched. Our study on the transient absorption of these complexes demonstrated that they all possessed broadband triplet excited-state absorption in the 400-800 nm region. Pyrenyl substitution of one or more tpy ligands, as in Ir4 and Ir5, increased the lifetimes of the lowest triplet excited state and the singlet oxygen (1O2) production efficiencies. Ir1-Ir5 were nontoxic toward SK-MEL-28 cells, with photocytotoxicities that varied from 0.18 to 153 µM. Among them, Ir4 had the highest 1O2 quantum yield (0.81) in cell-free conditions, showing the largest photocytotoxicity against SK-MEL-28 cells for Ir(III) PSs to date, and was the most efficient generator of reactive oxygen species (ROS) in vitro. Ir4 possessed a very large phototherapeutic index (PI = dark EC50 / light EC50) of >1657, the largest reported for an Ir(III) complex photosensitizer upon broadband visible light (400-700 nm) activation. Ir4 also exhibited a very strong PDT effect toward MCF-7 breast cancer cells and its xenograft tumor model. Upon 450-nm light activation, Ir4 dramatically inhibited the xenograft tumor growth and exhibited negligible side effects upon PDT treatment.
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Affiliation(s)
- Bingqing Liu
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND 58108–6050, USA
| | - Susan Monro
- Department of Chemistry, Acadia University, 6 University Avenue, Wolfville, NS B4P 2R6, Canada
| | - Zhike Li
- Key Laboratory of Combinatorial Biosynthesis and Drug Discovery (MOE), Hubei Province Engineering and Technology Research Center for Fluorinated Pharmaceuticals, School of Pharmaceutical Sciences, Wuhan University, Wuhan 430071, P. R. China
| | - Mohammed A. Jabed
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND 58108–6050, USA
| | - Daniel Ramirez
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND 58108–6050, USA
| | - Colin G. Cameron
- Department of Chemistry and Biochemistry, University of North Carolina at Greensboro, Greensboro, NC 27402–6170, USA
| | - Katsuya Colón
- Department of Chemistry and Biochemistry, University of North Carolina at Greensboro, Greensboro, NC 27402–6170, USA
| | - John Roque
- Department of Chemistry and Biochemistry, University of North Carolina at Greensboro, Greensboro, NC 27402–6170, USA
| | - Svetlana Kilina
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND 58108–6050, USA
| | - Jian Tian
- Key Laboratory of Combinatorial Biosynthesis and Drug Discovery (MOE), Hubei Province Engineering and Technology Research Center for Fluorinated Pharmaceuticals, School of Pharmaceutical Sciences, Wuhan University, Wuhan 430071, P. R. China
| | - Sherri A. McFarland
- Department of Chemistry, Acadia University, 6 University Avenue, Wolfville, NS B4P 2R6, Canada
- Department of Chemistry and Biochemistry, University of North Carolina at Greensboro, Greensboro, NC 27402–6170, USA
| | - Wenfang Sun
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND 58108–6050, USA
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Liu B, Lystrom L, Brown SL, Hobbie EK, Kilina S, Sun W. Impact of Benzannulation Site at the Diimine (N^N) Ligand on the Excited-State Properties and Reverse Saturable Absorption of Biscyclometalated Iridium(III) Complexes. Inorg Chem 2019; 58:5483-5493. [PMID: 31060198 DOI: 10.1021/acs.inorgchem.8b03162] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Ten biscyclometalated monocationic Ir(III) complexes were synthesized and studied to elucidate the effects of extending π-conjugation of the diimine ligand (N^N = 2,2'-bipyridine in Ir1, 2-(pyridin-2-yl)quinoline in Ir2, 2-(pyridin-2-yl)[6,7]benzoquinoline in Ir3, 2-(pyridin-2-yl)-[7,8]benzoquinoline in Ir4, phenanthroline in Ir5, benzo[ f][1,10]phenanthroline in Ir6, naphtho[2,3- f][1,10]phenanthroline in Ir7, 2,2'-bisquinoline in Ir8, 3,3'-biisoquinoline in Ir9, and 1,1'-biisoquinoline in Ir10) via benzannulation at 2,2'-bipyridine on the excited-state properties and reverse saturable absorption (RSA) of these complexes. Either a bathochromic or a hypsochromic shift of the charge-transfer absorption band and emission spectrum was observed depending on the benzannulation site at the 2,2'-bipyridine ligand. Benzannulation at the 3,4-/3',4'-position or 5,6-/5',6'-position of 2,2'-bipyridine ligand or at the 6,7-position of the quinoline ring on the N^N ligand caused red-shifted charge-transfer absorption band and emission band for complexes Ir2, Ir8, Ir10 vs Ir1 and Ir3 vs Ir2, while benzannulation at the 4,5-/4',5'-position of 2,2'-bipyridine ligand or at the 7,8-position of the quinoline ring on the N^N ligand induced a blue shift of the charge-transfer absorption and emission bands for complex Ir9 vs Ir1 and Ir4 vs Ir2. However, benzannulation at the 2,2',3,3'-position of 2,2'-bipyridine or 5,6-position of phenanthroline ligand had no impact on the energy of the charge-transfer absorption band and emission band of complexes Ir5-Ir7 compared with those of Ir1. The observed phenomenon was explained by the frontier molecular orbital (FMO) symmetry analysis. Site-dependent benzannulation also impacted the spectral feature and intensity of the triplet transient absorption spectra and lifetimes drastically. Consequently, the RSA strength of these complexes varied with a trend of Ir7 > Ir5 ≈ Ir6 ≈ Ir1 > Ir3 > Ir2 > Ir10 > Ir4 > Ir8 > Ir9 at 532 nm for 4.1 ns laser pulses.
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Affiliation(s)
- Bingqing Liu
- Department of Chemistry and Biochemistry , North Dakota State University , Fargo , North Dakota 58108-6050 , United States
| | - Levi Lystrom
- Department of Chemistry and Biochemistry , North Dakota State University , Fargo , North Dakota 58108-6050 , United States
| | - Samuel L Brown
- Materials and Nanotechnology Program , North Dakota State University , Fargo , North Dakota 58108-6050 , United States
| | - Erik K Hobbie
- Materials and Nanotechnology Program , North Dakota State University , Fargo , North Dakota 58108-6050 , United States
| | - Svetlana Kilina
- Department of Chemistry and Biochemistry , North Dakota State University , Fargo , North Dakota 58108-6050 , United States
| | - Wenfang Sun
- Department of Chemistry and Biochemistry , North Dakota State University , Fargo , North Dakota 58108-6050 , United States
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Liu B, Lystrom L, Cameron CG, Kilina S, McFarland SA, Sun W. Monocationic Iridium(III) Complexes with Far‐Red Charge‐Transfer Absorption and Near‐IR Emission: Synthesis, Photophysics, and Reverse Saturable Absorption. Eur J Inorg Chem 2019. [DOI: 10.1002/ejic.201900156] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Bingqing Liu
- Department of Chemistry and Biochemistry North Dakota State University Fargo North Dakota 58108‐6050 USA
| | - Levi Lystrom
- Department of Chemistry and Biochemistry North Dakota State University Fargo North Dakota 58108‐6050 USA
| | - Colin G. Cameron
- Department of Chemistry and Biochemistry University of North Carolina at Greensboro Greensboro North Carolina 27402‐6170 USA
| | - Svetlana Kilina
- Department of Chemistry and Biochemistry North Dakota State University Fargo North Dakota 58108‐6050 USA
| | - Sherri A. McFarland
- Department of Chemistry and Biochemistry University of North Carolina at Greensboro Greensboro North Carolina 27402‐6170 USA
| | - Wenfang Sun
- Department of Chemistry and Biochemistry North Dakota State University Fargo North Dakota 58108‐6050 USA
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Wang L, Monro S, Cui P, Yin H, Liu B, Cameron CG, Xu W, Hetu M, Fuller A, Kilina S, McFarland SA, Sun W. Heteroleptic Ir(III)N 6 Complexes with Long-Lived Triplet Excited States and in Vitro Photobiological Activities. ACS Appl Mater Interfaces 2019; 11:3629-3644. [PMID: 30608121 PMCID: PMC6355354 DOI: 10.1021/acsami.8b14744] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
A series of cationic heteroleptic iridium(III) complexes bearing tris-diimine ligands [Ir(phen)2(R-phen)]3+ (R-phen = phenanthroline (1), 3,8-diphenylphenanthroline (2), 3,8-dipyrenylphenanthroline (3), 3-phenylphenanthroline (4), 3-pyrenylphenanthroline (5), and 3,8-diphenylethynylphenanthroline (6)) were synthesized and characterized. These complexes possessed phen ligand-localized 1π,π* transitions below 300 nm, and charge transfer (1CT) and/or 1π,π* transitions between 300 and 520 nm. In 1, 2, 4, and 6, the low-energy bands were mixed 1CT/1π,π*. However, the increased π-donating ability of the pyrenyl substituent(s) in 3 and 5 split the low-energy bands into a pyrene-based 1π,π* transition at 300-380 nm and an intraligand charge transfer (1ILCT) transition at 380-520 nm. All complexes were emissive at room temperature in CH3CN, but the parentage of the emitting state varied depending on the R substituent(s). Complex 1 exhibited predominantly phen ligand-localized 3π,π* emission mixed with metal-to-ligand charge transfer (3MLCT) character, whereas the emission of 2, 4, and 6 was predominantly from the excited-state with 3π,π*/3ILCT/3MLCT character. The emission from 3 and 5 was dominated by pyrene-based 3π,π* states mixed with 3ILCT character. The different natures of the lowest triplet excited states were also reflected by the different spectral features and lifetimes of the triplet transient absorption of these complexes. Complexes 3 and 5 had singlet oxygen quantum yields as high as 81 and 72%, respectively. Both gave submicromolar phototoxicities toward cancer cells (SK-MEL-28 human melanoma) and bacteria ( S. aureus and S. mutans) with visible-light activation (and marginal to no photobiological activity with red light). Their visible-light phototherapeutic indices (PIs) toward SK-MEL-28 cells were 248 for 3 and >435 for 5; PIs were lower in bacteria (≤62) because of their inherent antimicrobial activities. Both complexes were shown to produce substantial amounts of intracellular reactive oxygen species (ROS), which may account for their photobiological activities.
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Affiliation(s)
- Li Wang
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108-6050, United States
| | - Susan Monro
- Department of Chemistry, Acadia University, 6 University Avenue, Wolfville, NS B4P 2R6, Canada
| | - Peng Cui
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108-6050, United States
- Materials and Nanotechnology Program, North Dakota State University, Fargo, North Dakota 58108-6050, United States
| | - Huimin Yin
- Department of Chemistry, Acadia University, 6 University Avenue, Wolfville, NS B4P 2R6, Canada
| | - Bingqing Liu
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108-6050, United States
| | - Colin G. Cameron
- Department of Chemistry and Biochemistry, University of North Carolina at Greensboro, Greensboro, North Carolina 27402-6170, United States
| | - Wei Xu
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108-6050, United States
| | - Marc Hetu
- Department of Chemistry, Acadia University, 6 University Avenue, Wolfville, NS B4P 2R6, Canada
| | - Anderson Fuller
- Department of Chemistry, Acadia University, 6 University Avenue, Wolfville, NS B4P 2R6, Canada
| | - Svetlana Kilina
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108-6050, United States
| | - Sherri A. McFarland
- Department of Chemistry, Acadia University, 6 University Avenue, Wolfville, NS B4P 2R6, Canada
- Department of Chemistry and Biochemistry, University of North Carolina at Greensboro, Greensboro, North Carolina 27402-6170, United States
| | - Wenfang Sun
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108-6050, United States
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25
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Liu B, Lystrom L, Kilina S, Sun W. Effects of Varying the Benzannulation Site and π Conjugation of the Cyclometalating Ligand on the Photophysics and Reverse Saturable Absorption of Monocationic Iridium(III) Complexes. Inorg Chem 2018; 58:476-488. [PMID: 30525520 DOI: 10.1021/acs.inorgchem.8b02714] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
A series of monocationic iridium(III) complexes, [Ir(C^N)2(pqu)]+PF6- [pqu = 2-(pyridin-2-yl)quinoline, C^N = 2-phenylquinoline (1), 3-phenylisoquinoline (2), 1-phenylisoquinoline (3), benzo[ h]quinoline (4), 2-(pyridin-2-yl)naphthalene (5), 1-(pyridin-2-yl)naphthalene (6), 2-(phenanthren-9-yl)pyridine (7), 2-phenylbenzo[ g]quinoline (8), 2-(naphthalen-2-yl)quinoline (9), and 2-(naphthalen-2-yl)benzo[ g]quinoline (10)], were synthesized in this work. These complexes bear C^N ligands with varied degrees of π conjugation and sites of benzannulation, allowing for elucidation of the effects of the benzannulation site at the C^N ligand on the photophysics of the complexes. Ultraviolet-visible (UV-vis) absorption and emission of the complexes were systematically investigated via spectroscopic techniques and time-dependent density functional theory calculations. Their triplet excited-state absorption and reverse saturable absorption (RSA) were studied by nanosecond transient absorption (TA) spectroscopy and nonlinear transmission techniques. The fusion of phenyl ring(s) to the phenyl ring or the 4 and 5 positions of the pyridyl ring of the C^N ligand resulted in red-shifted UV-vis absorption and emission spectra in complexes 2, 5-7, 9, and 10 compared to those of the parent complex 0, while their triplet lifetimes and emission quantum yields were significantly reduced. In contrast, the fusion of one phenyl ring to the other sites of the pyridyl group of the C^N ligand showed an insignificant impact on the energies of the lowest singlet (S1) and triplet (T1) excited states in complexes 1, 3, and 4 but noticeably affected their TA spectral features. The fusion of the naphthyl group to the 5 and 6 and positions at the pyridyl ring did not influence the S1 energy of complex 8 but altered the nature of the T1 states in 8 and 10 by switching them to the benzo[ g]quinoline-localized 3π,π* state, which resulted in completely different emission and TA spectra in these two complexes. The site-dependent variations of the ground- and excited-state absorption induced strong but varied RSA from these complexes for 4.1-ns laser pulses at 532 nm, with the RSA strength decreasing in the trend of 3 > 7 ≈ 4 ≈ 9 ≈ 6 > 8 ≈ 1 ≈ 2 ≈ 5 > 10.
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Affiliation(s)
- Bingqing Liu
- Department of Chemistry and Biochemistry , North Dakota State University , Fargo , North Dakota 58108-6050 , United States
| | - Levi Lystrom
- Department of Chemistry and Biochemistry , North Dakota State University , Fargo , North Dakota 58108-6050 , United States
| | - Svetlana Kilina
- Department of Chemistry and Biochemistry , North Dakota State University , Fargo , North Dakota 58108-6050 , United States
| | - Wenfang Sun
- Department of Chemistry and Biochemistry , North Dakota State University , Fargo , North Dakota 58108-6050 , United States
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Abstract
Novel N6-coordinated Ir(iii) complexes bearing polypyridyl ligands were synthesized and characterized. In comparison to their Ru(ii) analogs, these Ir(iii) complexes showed blue-shifted UV-vis absorption and emission spectra, but dramatically increased triplet lifetimes with much broader and stronger triplet excited-state absorption.
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Affiliation(s)
- Li Wang
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108-6050, USA.
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He X, Velizhanin KA, Bullard G, Bai Y, Olivier JH, Hartmann NF, Gifford BJ, Kilina S, Tretiak S, Htoon H, Therien MJ, Doorn SK. Solvent- and Wavelength-Dependent Photoluminescence Relaxation Dynamics of Carbon Nanotube sp 3 Defect States. ACS Nano 2018; 12:8060-8070. [PMID: 29995379 DOI: 10.1021/acsnano.8b02909] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Photoluminescent sp3 defect states introduced to single wall carbon nanotubes (SWCNTs) through low-level covalent functionalization create new photophysical behaviors and functionality as a result of defect sites acting as exciton traps. Evaluation of relaxation dynamics in varying dielectric environments can aid in advancing a more complete description of defect-state relaxation pathways and electronic structure. Here, we exploit helical wrapping polymers as a route to suspending (6,5) SWCNTs covalently functionalized with 4-methoxybenzene in solvent systems including H2O, D2O, methanol, dimethylformamide, tetrahydrofuran, and toluene, spanning a range of dielectric constants from 80 to 3. Defect-state photoluminescence decays were measured as a function of emission wavelength and solvent environment. Emission decays are biexponential, with short lifetime components on the order of 65 ps and long components ranging from around 100 to 350 ps. Both short and long decay components increase as emission wavelength increases, while only the long lifetime component shows a solvent dependence. We demonstrate that the wavelength dependence is a consequence of thermal detrapping of defect-state excitons to produce mobile E11 excitons, providing an important mechanism for loss of defect-state population. Deeper trap states (i.e., those emitting at longer wavelengths) result in a decreased rate for thermal loss. The solvent-independent behavior of the short lifetime component is consistent with its assignment as the characteristic time for redistribution of exciton population between bright and dark defect states. The solvent dependence of the long lifetime component is shown to be consistent with relaxation via an electronic to vibrational energy transfer mechanism, in which energy is resonantly lost to solvent vibrations in a complementary mechanism to multiphonon decay processes.
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Affiliation(s)
- Xiaowei He
- Center for Integrated Nanotechnologies, Materials Physics and Applications Division , Los Alamos National Laboratory , Los Alamos , New Mexico 87545 , United States
| | - Kirill A Velizhanin
- Theoretical Division , Los Alamos National Laboratory , Los Alamos , New Mexico 87545 , United States
| | - George Bullard
- Department of Chemistry, French Family Science Center , Duke University , Durham , North Carolina 27708 , United States
| | - Yusong Bai
- Department of Chemistry, French Family Science Center , Duke University , Durham , North Carolina 27708 , United States
| | - Jean-Hubert Olivier
- Department of Chemistry, French Family Science Center , Duke University , Durham , North Carolina 27708 , United States
| | - Nicolai F Hartmann
- Center for Integrated Nanotechnologies, Materials Physics and Applications Division , Los Alamos National Laboratory , Los Alamos , New Mexico 87545 , United States
| | - Brendan J Gifford
- Theoretical Division , Los Alamos National Laboratory , Los Alamos , New Mexico 87545 , United States
- Center for Nonlinear Sciences , Los Alamos National Laboratory , Los Alamos , New Mexico 87545 , United States
- Department of Chemistry and Biochemistry , North Dakota State University , Fargo , North Dakota 58108 , United States
| | - Svetlana Kilina
- Department of Chemistry and Biochemistry , North Dakota State University , Fargo , North Dakota 58108 , United States
| | - Sergei Tretiak
- Center for Integrated Nanotechnologies, Materials Physics and Applications Division , Los Alamos National Laboratory , Los Alamos , New Mexico 87545 , United States
- Theoretical Division , Los Alamos National Laboratory , Los Alamos , New Mexico 87545 , United States
| | - Han Htoon
- Center for Integrated Nanotechnologies, Materials Physics and Applications Division , Los Alamos National Laboratory , Los Alamos , New Mexico 87545 , United States
| | - Michael J Therien
- Department of Chemistry, French Family Science Center , Duke University , Durham , North Carolina 27708 , United States
| | - Stephen K Doorn
- Center for Integrated Nanotechnologies, Materials Physics and Applications Division , Los Alamos National Laboratory , Los Alamos , New Mexico 87545 , United States
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Liu B, Monro S, Lystrom L, Cameron CG, Colon K, Yin H, Kilina S, McFarland SA, Sun W. Photophysical and Photobiological Properties of Dinuclear Iridium(III) Bis-tridentate Complexes. Inorg Chem 2018; 57:9859-9872. [PMID: 30091916 PMCID: PMC6337720 DOI: 10.1021/acs.inorgchem.8b00789] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A series of cationic dinuclear iridium(III) complexes (Ir1-Ir5) bearing terpyridine-capped fluorenyl bridging ligands and different polypyridyl or cyclometalating terminal tridentate ligands were synthesized, characterized, and evaluated for their photophysical and photobiological activities. The influence of the bridging and terminal ligands on the photophysical properties of the complexes was investigated by UV-vis absorption, emission, and transient absorption spectroscopy and simulated by TDDFT calculations. All of the complexes displayed strong bridging-ligand localized visible 1π,π* absorption and red- or near-infrared phosphorescence as well as broad triplet excited-state absorption across both visible and NIR wavelengths. These triplet states were assigned as predominantly 3π,π* for Ir1 (τ = 3.1 μs) and Ir4 (τ = 48 μs) and 3CT (charge transfer) for Ir2, Ir3, and Ir5 (τ = 1.7-2.7 μs). Complexes Ir1-Ir5 acted as in vitro photodynamic therapy (PDT) agents toward human SK-MEL-28 melanoma cells when activated with visible light, with submicromolar photocytotoxicity and phototherapeutic indices ranging from 20 to almost 300. The in vitro PDT effects with visible light did not correlate with singlet oxygen (1O2) quantum yields or DNA photocleaving capacity probed under cell-free conditions. All of the Ir(III) complexes phosphoresced brightly when associated with compromised cells (with or without light treatment) and exhibited photoactivated cellular uptake, highlighting the theranostic potential of this new class of Ir(III) complex photosensitizers.
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Affiliation(s)
- Bingqing Liu
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND 58108-6050, USA
| | - Susan Monro
- Department of Chemistry, Acadia University, 6 University Avenue, Wolfville, NS B4P 2R6, Canada
| | - Levi Lystrom
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND 58108-6050, USA
| | - Colin G. Cameron
- Department of Chemistry and Biochemistry, University of North Carolina at Greensboro, Greensboro, NC 27402-6170, USA
| | - Katsuya Colon
- Department of Chemistry and Biochemistry, University of North Carolina at Greensboro, Greensboro, NC 27402-6170, USA
| | - Huimin Yin
- Department of Chemistry, Acadia University, 6 University Avenue, Wolfville, NS B4P 2R6, Canada
| | - Svetlana Kilina
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND 58108-6050, USA
| | - Sherri A. McFarland
- Department of Chemistry, Acadia University, 6 University Avenue, Wolfville, NS B4P 2R6, Canada
- Department of Chemistry and Biochemistry, University of North Carolina at Greensboro, Greensboro, NC 27402-6170, USA
| | - Wenfang Sun
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND 58108-6050, USA
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Gifford BJ, Sifain AE, Htoon H, Doorn SK, Kilina S, Tretiak S. Correction Scheme for Comparison of Computed and Experimental Optical Transition Energies in Functionalized Single-Walled Carbon Nanotubes. J Phys Chem Lett 2018; 9:2460-2468. [PMID: 29678108 DOI: 10.1021/acs.jpclett.8b00653] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Covalent functionalization of single-walled carbon nanotubes (SWCNTs) introduces red-shifted emission features in the near-infrared spectral range due to exciton localization around the defect site. Such chemical modifications increase their potential use as near-infrared emitters and single-photon sources in telecommunications applications. Density functional theory (DFT) studies using finite-length tube models have been used to calculate their optical transition energies. Predicted energies are typically blue-shifted compared to experiment due to methodology errors including imprecise self-interaction corrections in the density functional and finite-size basis sets. Furthermore, artificial quantum confinement in finite models cannot be corrected by a constant-energy shift since they depend on the degree of exciton localization. Herein, we present a method that corrects the emission energies predicted by time-dependent DFT. Confinement and methodology errors are separately estimated using experimental data for unmodified tubes. Corrected emission energies are in remarkable agreement with experiment, suggesting the value of this straightforward method toward predicting and interpreting the optical features of functionalized SWCNTs.
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Affiliation(s)
- Brendan J Gifford
- Department of Chemistry and Biochemistry , North Dakota State University , Fargo , North Dakota 58108 , United States
| | - Andrew E Sifain
- Department of Physics and Astronomy , University of Southern California , Los Angeles , California 90089 , United States
| | | | | | - Svetlana Kilina
- Department of Chemistry and Biochemistry , North Dakota State University , Fargo , North Dakota 58108 , United States
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Pokhodnya K, Anderson K, Kilina S, Dandu N, Boudjouk P. Mechanism of Charged, Neutral, Mono-, and Polyatomic Donor Ligand Coordination to Perchlorinated Cyclohexasilane (Si 6Cl 12). J Phys Chem A 2018; 122:4067-4075. [PMID: 29589757 DOI: 10.1021/acs.jpca.7b11052] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We report the detailed computational study of several perchlorinated cyclohexasilane (Si6Cl12)-based inverse sandwich compounds. It was found that regardless of the donor ligand size and charge, for example, Cl- and CN- anions or neutral HCN and NCPh nitriles, their coordination to the puckered Si6Cl12 ring results in its flattening. The NBO and CDA studies of the complexes showed that coordination occurs due to hybridization of low-lying antibonding σ*(Si-Cl) and σ*(Si-Si) unoccupied molecular orbitals (UMOs) of Si6Cl12 and occupied molecular orbitals (OMOs) of donor molecules (predominantly lone-pair-related), resulting in donor-to-ring charge transfer accompanied by complex stabilization and ring flattening. It is known that the Si6 ring distortion results from vibronic coupling of OMO and UMO pairs (pseudo-Jahn-Teller effect, PJT). Consequently, the Si6 ring flattening most probably occurs due to suppression of the PJT effect in all of the studied compounds. In this paper, the stabilization energy E(2) associated with donor-acceptor charge transfer (delocalization) was estimated using NBO analysis for [Si6Cl12·2Cl]2-, [Si6Cl12·2(NC)]2-, Si6Cl12·2(NCH), and Si6Cl12·2(NCPh). It was found that the polarizability of the donor might significantly affect the stabilization energy value (Cl- > CN- > HCN). For the neutral complexes, the E(2) value is correlated with the charge on the nitrogen atoms. All of these factors, that is, specific donor E(2) value, charge transfer, complex MO energy diagrams, and so on, should be taken into account when choosing the ligands suitable for forming Si-based 1D compounds and other nanoscale materials.
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Affiliation(s)
- Konstantin Pokhodnya
- Department of Chemistry and Biochemistry , North Dakota State University , Fargo , North Dakota 58108 , United States
| | - Kenneth Anderson
- Department of Chemistry and Biochemistry , North Dakota State University , Fargo , North Dakota 58108 , United States
| | - Svetlana Kilina
- Department of Chemistry and Biochemistry , North Dakota State University , Fargo , North Dakota 58108 , United States
| | - Naveen Dandu
- Department of Chemistry and Biochemistry , North Dakota State University , Fargo , North Dakota 58108 , United States
| | - Philip Boudjouk
- Department of Chemistry and Biochemistry , North Dakota State University , Fargo , North Dakota 58108 , United States
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Wang C, Lystrom L, Yin H, Hetu M, Kilina S, McFarland SA, Sun W. Increasing the triplet lifetime and extending the ground-state absorption of biscyclometalated Ir(iii) complexes for reverse saturable absorption and photodynamic therapy applications. Dalton Trans 2018; 45:16366-16378. [PMID: 27711764 DOI: 10.1039/c6dt02416e] [Citation(s) in RCA: 70] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The synthesis, photophysics, reverse saturable absorption, and photodynamic therapeutic effect of six cationic biscyclometalated Ir(iii) complexes (1-6) with extended π-conjugation on the diimine ligand and/or the cyclometalating ligands are reported in this paper. All complexes possess ligand-localized 1π,π* absorption bands below 400 nm and charge-transfer absorption bands above 400 nm. They are all emissive in the 500-800 nm range in deoxygenated solutions at room temperature. All complexes exhibit strong and broad triplet excited-state absorption at 430-800 nm, and thus strong reverse saturable absorption for ns laser pulses at 532 nm. Complexes 1-4 are strong reverse saturable absorbers at 532 nm, while complex 6 could be a good candidate as a broadband reverse saturable absorber at 500-850 nm. The degree of π-conjugation of the diimine ligand mainly influences the 1π,π* transitions in their UV-vis absorption spectra, while the degree of π-conjugation of the cyclometalating ligand primarily affects the nature and energies of the lowest singlet and emitting triplet excited states. However, the lowest-energy triplet excited states for complexes 3-6 that contain the same benzo[i]dipyrido[3,2-a:2',3'-c]phenazine (dppn) diimine ligand but different cyclometalating ligands remain the same as the dppn ligand-localized 3π,π* state, which gives rise to the long-lived, strong excited-state absorption in the visible to the near-IR region. All of the complexes exhibit a photodynamic therapeutic effect upon visible or red light activation, with complex 6 possessing the largest phototherapeutic index reported to date (>400) for an Ir(iii) complex. Interactions with biological targets such as DNA suggest that a novel mechanism of action may be at play for the photosensitizing effect. These Ir(iii) complexes also produce strong intracellular luminescence that highlights their potential as theranostic agents.
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Affiliation(s)
- Chengzhe Wang
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND 58108-6050, USA.
| | - Levi Lystrom
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND 58108-6050, USA.
| | - Huimin Yin
- Department of Chemistry, Acadia University, 6 University Avenue, Wolfville, NS B4P 2R6, Canada.
| | - Marc Hetu
- Department of Chemistry, Acadia University, 6 University Avenue, Wolfville, NS B4P 2R6, Canada.
| | - Svetlana Kilina
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND 58108-6050, USA.
| | - Sherri A McFarland
- Department of Chemistry, Acadia University, 6 University Avenue, Wolfville, NS B4P 2R6, Canada. and Department of Chemistry and Biochemistry, University of North Carolina at Greensboro, Greensboro, NC 27402-6170, USA.
| | - Wenfang Sun
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND 58108-6050, USA.
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Zhu X, Cui P, Kilina S, Sun W. Multifunctional Cationic Iridium(III) Complexes Bearing 2-Aryloxazolo[4,5-f][1,10]phenanthroline (N^N) Ligand: Synthesis, Crystal Structure, Photophysics, Mechanochromic/Vapochromic Effects, and Reverse Saturable Absorption. Inorg Chem 2017; 56:13715-13731. [PMID: 29083889 DOI: 10.1021/acs.inorgchem.7b01472] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A series of 2-aryloxazolo[4,5-f][1,10]phenanthroline ligands (N^N ligands) and their cationic iridium(III) complexes (1-11, aryl = 4-NO2-phenyl (1), 4-Br-phenyl (2), Ph (3), 4-NPh2-phenyl (4), 4-NH2-phenyl (5), pyridin-4-yl (6), naphthalen-1-yl (7), naphthalen-2-yl (8), phenanthren-9-yl (9), anthracen-9-yl (10), and pyren-1-yl (11)) were synthesized and characterized. By introducing different electron-donating or electron-withdrawing substituents at the 4-position of the 2-phenyl ring (1-5), or different aromatic substituents with varied degrees of π-conjugation (6-11) on oxazolo[4,5-f][1,10]phenanthroline ligand, we aim to understand the effects of terminal substituents at the N^N ligands on the photophysics of cationic Ir(III) complexes using both spectroscopic methods and quantum chemistry calculations. Complexes with the 4-R-phenyl substituents adopted an almost coplanar structure with the oxazolo[4,5-f][1,10]phenanthroline motif, while the polycyclic aryl substituents (except for naphthalen-2-yl) were twisted away from the oxazolo[4,5-f][1,10]phenanthroline motif. All complexes possessed strong absorption bands below 350 nm that emanated from the ligand-localized 1π,π*/1ILCT (intraligand charge transfer) transitions, mixed with 1LLCT (ligand-to-ligand charge transfer)/1MLCT (metal-to-ligand charge transfer) transitions. At the range of 350-570 nm, all complexes exhibited moderately strong 1ILCT/1LLCT/1MLCT transitions at 350-450 nm, and broad but very weak 3LLCT/3MLCT absorption at 450-570 nm. Most of the complexes demonstrated moderate to strong room temperature phosphorescence both in solution and in the solid state. Among them, complex 7 also manifested a drastic mechanochromic and vapochromic luminescence effect. Except for complexes 1 and 4 that contain NO2 or NPh2 substituent at the phenyl ring, respectively, all other complexes exhibited moderate to strong triplet excited-state absorption in the spectral region of 440-750 nm. Moderate to very strong reverse saturable absorption (RSA) of these complexes appeared at 532 nm for 4.1 ns laser pulses. The RSA strength followed the trend of 7 > 11 > 9 > 3 > 2 ≈ 4 > 5 ≈ 10 ≈ 6 ≈ 8 > 1. The photophysical studies revealed that the different 2-aryl substituents on the oxazole ring impacted the singlet and triplet excited-state characteristics dramatically, which in turn notably influenced the RSA of these complexes.
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Affiliation(s)
- Xiaolin Zhu
- Department of Chemistry and Biochemistry, North Dakota State University , Fargo, North Dakota 58108-6050, United States
| | - Peng Cui
- Department of Chemistry and Biochemistry, North Dakota State University , Fargo, North Dakota 58108-6050, United States.,Materials and Nanotechnology Program, North Dakota State University , Fargo, North Dakota 58105, United States
| | - Svetlana Kilina
- Department of Chemistry and Biochemistry, North Dakota State University , Fargo, North Dakota 58108-6050, United States
| | - Wenfang Sun
- Department of Chemistry and Biochemistry, North Dakota State University , Fargo, North Dakota 58108-6050, United States
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Kryjevski A, Mihaylov D, Kilina S, Kilin D. Multiple exciton generation in chiral carbon nanotubes: Density functional theory based computation. J Chem Phys 2017; 147:154106. [DOI: 10.1063/1.4997048] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Affiliation(s)
- Andrei Kryjevski
- Department of Physics, North Dakota State University, Fargo, North Dakota 58108, USA
| | - Deyan Mihaylov
- Department of Physics, North Dakota State University, Fargo, North Dakota 58108, USA
| | - Svetlana Kilina
- Department of Chemistry, North Dakota State University, Fargo, North Dakota 58108, USA
| | - Dmitri Kilin
- Department of Chemistry, North Dakota State University, Fargo, North Dakota 58108, USA
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34
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Pokhodnya K, Anderson K, Kilina S, Boudjouk P. Toward the Mechanism of Perchlorinated Cyclopentasilane (Si 5Cl 10) Ring Flattening in the [Si 5Cl 10·2Cl] 2- Dianion. J Phys Chem A 2017; 121:3494-3500. [PMID: 28406632 DOI: 10.1021/acs.jpca.6b12938] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We report the detailed computational study of flattening of the puckered Si5 ring by suppression of the pseudo-Jahn-Teller (PJT) effect through coordination of two Cl- anions to the molecule forming an inverse sandwich dianion [Si5Cl10·2Cl]2- complex. The PJT effect that causes nonplanarity of the Si5Cl10 structure (Cs) results from vibronic coupling of pairs of occupied molecular orbitals (OMOs) and unoccupied molecular orbitals (UMOs). It was shown that filling the intervenient molecular orbitals of puckered Si5Cl10 with valent electron pairs of Cl- donors suppresses the PJT effect, with the Si5 ring becoming planar (D5h) upon complex formation. In this paper, the stabilization energy E(2) associated with donor-acceptor charge transfer (delocalization) was estimated using NBO analysis for all studied inverse sandwich compounds [Si5Cl10·2X]2- (where X = F, Cl, Br). It was found that the polarizability of the donor ion might significantly affect the stabilization energy value and should be taken into account when choosing the ligands suitable for forming Si-based one-dimensional compounds and other nanoscale materials.
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Affiliation(s)
- Konstantin Pokhodnya
- Department of Chemistry and Biochemistry, North Dakota State University , Fargo, North Dakota 58108, United States
| | - Kenneth Anderson
- Department of Chemistry and Biochemistry, North Dakota State University , Fargo, North Dakota 58108, United States
| | - Svetlana Kilina
- Department of Chemistry and Biochemistry, North Dakota State University , Fargo, North Dakota 58108, United States
| | - Philip Boudjouk
- Department of Chemistry and Biochemistry, North Dakota State University , Fargo, North Dakota 58108, United States
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35
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Liu B, Lystrom L, Kilina S, Sun W. Tuning the Ground State and Excited State Properties of Monocationic Iridium(III) Complexes by Varying the Site of Benzannulation on Diimine Ligand. Inorg Chem 2017; 56:5361-5370. [PMID: 28398733 DOI: 10.1021/acs.inorgchem.7b00467] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Extending π-conjugation of the diimine ligand (N^N ligand) via benzannulation is a common way to tune the absorption and emission energies of cationic iridium(III) complexes. However, it can cause either a red- or blue-shift of the absorption and emission bands depending on the site of benzannulation. To understand the mechanism of changes in optical transitions upon benzannulation on the diimine ligand, a series of new cationic iridium(III) complexes [Ir(dppi)2(N^N)]PF6 (1-6) (where dppi =1,2-diphenylpyreno[4,5-d]imidazole; N^N = 2-(pyridin-2-yl)quinoline (1), 2-(pyridin-2-yl)[7,8]benzoquinoline (2), 2,2'-bisquinoline (3), 2-(quinolin-2-yl)[7,8]benzoquinoline (4), 2-(pyridin-2-yl)[6,7]benzoquinoline (5), 2-(quinolin-2-yl)[6,7]benzoquinoline (6)) containing diimine ligand with varied degrees of π-conjugation via benzannulation at different sites of the 2-(pyridin-2-yl)quinoline ligand were synthesized. Experimental results and density functional theory (DFT) calculations revealed that benzannulation at the 6,7-position of quinoline and/or the 5',6'-position of pyridine (3, 5, and 6) induced red-shifts in their absorption and emission bands with respect to the parent complex 1; while benzannulation at the 7,8-position of quinoline resulted in blue-shifts (2 vs 1 and 4 vs 3). This phenomenon was rationalized by the symmetry of the frontier molecular orbitals at the site of benzannulation, which stabilized or destabilized the lowest unoccupied molecular orbital (LUMO) upon interactions with 1,3-butadiene, while the energy of the highest occupied molecular orbital (HOMO) remained nearly the same. This discovery would enable a rational design of organic or organometallic compounds that have predetermined absorption and emission energies.
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Affiliation(s)
- Bingqing Liu
- Department of Chemistry and Biochemistry, North Dakota State University , Fargo, North Dakota 58108-6050, United States
| | - Levi Lystrom
- Department of Chemistry and Biochemistry, North Dakota State University , Fargo, North Dakota 58108-6050, United States
| | - Svetlana Kilina
- Department of Chemistry and Biochemistry, North Dakota State University , Fargo, North Dakota 58108-6050, United States
| | - Wenfang Sun
- Department of Chemistry and Biochemistry, North Dakota State University , Fargo, North Dakota 58108-6050, United States
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36
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Wang L, Yin H, Jabed MA, Hetu M, Wang C, Monro S, Zhu X, Kilina S, McFarland SA, Sun W. π-Expansive Heteroleptic Ruthenium(II) Complexes as Reverse Saturable Absorbers and Photosensitizers for Photodynamic Therapy. Inorg Chem 2017; 56:3245-3259. [PMID: 28263079 DOI: 10.1021/acs.inorgchem.6b02624] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Five heteroleptic tris-diimine ruthenium(II) complexes [RuL(N^N)2](PF6)2 (where L is 3,8-di(benzothiazolylfluorenyl)-1,10-phenanthroline and N^N is 2,2'-bipyridine (bpy) (1), 1,10-phenanthroline (phen) (2), 1,4,8,9-tetraazatriphenylene (tatp) (3), dipyrido[3,2-a:2',3'-c]phenazine (dppz) (4), or benzo[i]dipyrido[3,2-a:2',3'-c]phenazine (dppn) (5), respectively) were synthesized. The influence of π-conjugation of the ancillary ligands (N^N) on the photophysical properties of the complexes was investigated by spectroscopic methods and simulated by density functional theory (DFT) and time-dependent DFT. Their ground-state absorption spectra were characterized by intense absorption bands below 350 nm (ligand L localized 1π,π* transitions) and a featureless band centered at ∼410 nm (intraligand charge transfer (1ILCT)/1π,π* transitions with minor contribution from metal-to-ligand charge transfer (1MLCT) transition). For complexes 4 and 5 with dppz and dppn ligands, respectively, broad but very weak absorption (ε < 800 M-1 cm-1) was present from 600 to 850 nm, likely emanating from the spin-forbidden transitions to the triplet excited states. All five complexes showed red-orange phosphorescence at room temperature in CH2Cl2 solution with decreased lifetimes and emission quantum yields, as the π-conjugation of the ancillary ligands increased. Transient absorption (TA) profiles were probed in acetonitrile solutions at room temperature for all of the complexes. Except for complex 5 (which showed dppn-localized 3π,π* absorption with a long lifetime of 41.2 μs), complexes 1-4 displayed similar TA spectral features but with much shorter triplet lifetimes (1-2 μs). Reverse saturable absorption (RSA) was demonstrated for the complexes at 532 nm using 4.1 ns laser pulses, and the strength of RSA decreased in the order: 2 ≥ 1 ≈ 5 > 3 > 4. Complex 5 is particularly attractive as a broadband reverse saturable absorber due to its wide optical window (430-850 nm) and long-lived triplet lifetime in addition to its strong RSA at 532 nm. Complexes 1-5 were also probed as photosensitizing agents for in vitro photodynamic therapy (PDT). Most of them showed a PDT effect, and 5 emerged as the most potent complex with red light (EC50 = 10 μM) and was highly photoselective for melanoma cells (selectivity factor, SF = 13). Complexes 1-5 were readily taken up by cells and tracked by their intracellular luminescence before and after a light treatment. Diagnostic intracellular luminescence increased with increased π-conjugation of the ancillary N^N ligands despite diminishing cell-free phosphorescence in that order. All of the complexes penetrated the nucleus and caused DNA condensation in cell-free conditions in a concentration-dependent manner, which was not influenced by the identity of N^N ligands. Although the mechanism for photobiological activity was not established, complexes 1-5 were shown to exhibit potential as theranostic agents. Together the RSA and PDT studies indicate that developing new agents with long intrinsic triplet lifetimes, high yields for triplet formation, and broad ground-state absorption to near-infrared (NIR) in tandem is a viable approach to identifying promising agents for these applications.
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Affiliation(s)
- Li Wang
- Department of Chemistry and Biochemistry, North Dakota State University , Fargo, North Dakota 58108-6050, United States
| | - Huimin Yin
- Department of Chemistry, Acadia University , 6 University Avenue, Wolfville, NS B4P 2R6, Canada
| | - Mohammed A Jabed
- Department of Chemistry and Biochemistry, North Dakota State University , Fargo, North Dakota 58108-6050, United States
| | - Marc Hetu
- Department of Chemistry, Acadia University , 6 University Avenue, Wolfville, NS B4P 2R6, Canada
| | - Chengzhe Wang
- Department of Chemistry and Biochemistry, North Dakota State University , Fargo, North Dakota 58108-6050, United States
| | - Susan Monro
- Department of Chemistry, Acadia University , 6 University Avenue, Wolfville, NS B4P 2R6, Canada
| | - Xiaolin Zhu
- Department of Chemistry and Biochemistry, North Dakota State University , Fargo, North Dakota 58108-6050, United States
| | - Svetlana Kilina
- Department of Chemistry and Biochemistry, North Dakota State University , Fargo, North Dakota 58108-6050, United States
| | - Sherri A McFarland
- Department of Chemistry, Acadia University , 6 University Avenue, Wolfville, NS B4P 2R6, Canada.,Department of Chemistry and Biochemistry, University of North Carolina at Greensboro , Greensboro, North Carolina 27402-6170, United States
| | - Wenfang Sun
- Department of Chemistry and Biochemistry, North Dakota State University , Fargo, North Dakota 58108-6050, United States
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37
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Wang L, Yin H, Cui P, Hetu M, Wang C, Monro S, Schaller RD, Cameron CG, Liu B, Kilina S, McFarland SA, Sun W. Near-infrared-emitting heteroleptic cationic iridium complexes derived from 2,3-diphenylbenzo[g]quinoxaline as in vitro theranostic photodynamic therapy agents. Dalton Trans 2017; 46:8091-8103. [DOI: 10.1039/c7dt00913e] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Cationic iridium complexes are promising near-infrared-emittingin vitrotheranostic photodynamic therapy agents.
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Affiliation(s)
- Li Wang
- Department of Chemistry and Biochemistry
- North Dakota State University
- Fargo
- USA
| | - Huimin Yin
- Department of Chemistry
- Acadia University
- 6 University Avenue
- Wolfville
- Canada
| | - Peng Cui
- Department of Chemistry and Biochemistry
- North Dakota State University
- Fargo
- USA
- Materials and Nanotechnology Program
| | - Marc Hetu
- Department of Chemistry
- Acadia University
- 6 University Avenue
- Wolfville
- Canada
| | - Chengzhe Wang
- Department of Chemistry and Biochemistry
- North Dakota State University
- Fargo
- USA
| | - Susan Monro
- Department of Chemistry
- Acadia University
- 6 University Avenue
- Wolfville
- Canada
| | | | - Colin G. Cameron
- Department of Chemistry and Biochemistry
- University of North Carolina at Greensboro
- Greensboro
- USA
| | - Bingqing Liu
- Department of Chemistry and Biochemistry
- North Dakota State University
- Fargo
- USA
| | - Svetlana Kilina
- Department of Chemistry and Biochemistry
- North Dakota State University
- Fargo
- USA
| | | | - Wenfang Sun
- Department of Chemistry and Biochemistry
- North Dakota State University
- Fargo
- USA
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38
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39
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Zhu X, Lystrom L, Kilina S, Sun W. Tuning the Photophysics and Reverse Saturable Absorption of Heteroleptic Cationic Iridium(III) Complexes via Substituents on the 6,6′-Bis(fluoren-2-yl)-2,2′-biquinoline Ligand. Inorg Chem 2016; 55:11908-11919. [DOI: 10.1021/acs.inorgchem.6b02028] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Xiaolin Zhu
- Department
of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108-6050, United States
| | - Levi Lystrom
- Department
of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108-6050, United States
| | - Svetlana Kilina
- Department
of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108-6050, United States
| | - Wenfang Sun
- Department
of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108-6050, United States
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40
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Kryjevski A, Gifford B, Kilina S, Kilin D. Theoretical predictions on efficiency of bi-exciton formation and dissociation in chiral carbon nanotubes. J Chem Phys 2016; 145:154112. [DOI: 10.1063/1.4963735] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Andrei Kryjevski
- Department of Physics, North Dakota State University, Fargo, North Dakota 58108, USA
| | - Brendan Gifford
- Department of Chemistry, North Dakota State University, Fargo, North Dakota 58108, USA
| | - Svetlana Kilina
- Department of Chemistry, North Dakota State University, Fargo, North Dakota 58108, USA
| | - Dmitri Kilin
- Department of Chemistry, North Dakota State University, Fargo, North Dakota 58108, USA
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41
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Abstract
Using density functional theory (DFT) and time-dependent DFT (TDDFT), we investigate the effects of carboxylate groups on the electronic and optical properties of CdSe quantum dots (QDs).
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Affiliation(s)
- Patrick K. Tamukong
- Department of Chemistry and Biochemistry
- North Dakota State University
- Fargo
- USA
| | | | - Svetlana Kilina
- Department of Chemistry and Biochemistry
- North Dakota State University
- Fargo
- USA
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42
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Lu T, Wang C, Lystrom L, Pei C, Kilina S, Sun W. Effects of extending the π-conjugation of the acetylide ligand on the photophysics and reverse saturable absorption of Pt(ii) bipyridine bisacetylide complexes. Phys Chem Chem Phys 2016; 18:28674-28687. [DOI: 10.1039/c6cp02628a] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Extending the acetylide ligand π-conjugation diminishes the terminal substituent effect on the lowest excited states, but expands the triplet excited-state absorption to the near-IR region.
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Affiliation(s)
- Taotao Lu
- Department of Chemistry and Biochemistry
- North Dakota State University
- Fargo
- USA
| | - Chengzhe Wang
- Department of Chemistry and Biochemistry
- North Dakota State University
- Fargo
- USA
| | - Levi Lystrom
- Department of Chemistry and Biochemistry
- North Dakota State University
- Fargo
- USA
| | - Chengkui Pei
- Department of Chemistry and Biochemistry
- North Dakota State University
- Fargo
- USA
| | - Svetlana Kilina
- Department of Chemistry and Biochemistry
- North Dakota State University
- Fargo
- USA
| | - Wenfang Sun
- Department of Chemistry and Biochemistry
- North Dakota State University
- Fargo
- USA
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43
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Li Z, Li H, Gifford BJ, Peiris WDN, Kilina S, Sun W. Synthesis, photophysics, and reverse saturable absorption of 7-(benzothiazol-2-yl)-9,9-di(2-ethylhexyl)-9H-fluoren-2-yl tethered [Ir(bpy)(ppy)2]PF6 and Ir(ppy)3 complexes (bpy = 2,2′-bipyridine, ppy = 2-phenylpyridine). RSC Adv 2016. [DOI: 10.1039/c5ra20084a] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Both the charges and benzothiazolylfluorenyl pendant on the 2-phenylpyridine ligand influence the photophysics and reverse saturable absorption of Ir(iii) complexes.
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Affiliation(s)
- Zhongjing Li
- Department of Chemistry and Biochemistry
- North Dakota State University
- Fargo
- USA
| | - Hui Li
- Department of Chemistry and Biochemistry
- North Dakota State University
- Fargo
- USA
| | - Brendan J. Gifford
- Department of Chemistry and Biochemistry
- North Dakota State University
- Fargo
- USA
| | | | - Svetlana Kilina
- Department of Chemistry and Biochemistry
- North Dakota State University
- Fargo
- USA
| | - Wenfang Sun
- Department of Chemistry and Biochemistry
- North Dakota State University
- Fargo
- USA
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44
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Miller JB, Dandu N, Velizhanin KA, Anthony RJ, Kortshagen UR, Kroll DM, Kilina S, Hobbie EK. Enhanced Luminescent Stability through Particle Interactions in Silicon Nanocrystal Aggregates. ACS Nano 2015; 9:9772-9782. [PMID: 26348831 DOI: 10.1021/acsnano.5b02676] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Close-packed assemblies of ligand-passivated colloidal nanocrystals can exhibit enhanced photoluminescent stability, but the origin of this effect is unclear. Here, we use experiment, simulation, and ab initio computation to examine the influence of interparticle interactions on the photoluminescent stability of silicon nanocrystal aggregates. The time-dependent photoluminescence emitted by structures ranging in size from a single quantum dot to agglomerates of more than a thousand is compared with Monte Carlo simulations of noninteracting ensembles using measured single-particle blinking data as input. In contrast to the behavior typically exhibited by the metal chalcogenides, the measured photoluminescent stability shows an enhancement with respect to the noninteracting scenario with increasing aggregate size. We model this behavior using time-dependent density functional theory calculations of energy transfer between neighboring nanocrystals as a function of nanocrystal size, separation, and the presence of charge and/or surface-passivation defects. Our results suggest that rapid exciton transfer from "bright" nanocrystals to surface trap states in nearest-neighbors can efficiently fill such traps and enhance the stability of emission by promoting the radiative recombination of slowly diffusing excited electrons.
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Affiliation(s)
- Joseph B Miller
- North Dakota State University , Fargo, North Dakota 58108, United States
| | - Naveen Dandu
- North Dakota State University , Fargo, North Dakota 58108, United States
| | - Kirill A Velizhanin
- Theoretical Division, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States
| | - Rebecca J Anthony
- University of Minnesota , Minneapolis, Minnesota 55455, United States
| | - Uwe R Kortshagen
- University of Minnesota , Minneapolis, Minnesota 55455, United States
| | - Daniel M Kroll
- North Dakota State University , Fargo, North Dakota 58108, United States
| | - Svetlana Kilina
- North Dakota State University , Fargo, North Dakota 58108, United States
| | - Erik K Hobbie
- North Dakota State University , Fargo, North Dakota 58108, United States
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45
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Liu R, Dandu N, McCleese C, Li Y, Lu T, Li H, Yost D, Wang C, Kilina S, Burda C, Sun W. Influence of a Naphthaldiimide Substituent at the Diimine Ligand on the Photophysics and Reverse Saturable Absorption of Pt
II
Diimine Complexes and Cationic Ir
III
Complexes. Eur J Inorg Chem 2015. [DOI: 10.1002/ejic.201500882] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Rui Liu
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108‐6050, USA, http://https://www.ndsu.edu/chemistry/people/faculty/sun.html
- Department of Applied Chemistry, College of Sciences, Nanjing Tech University, Nanjing 211816, P.R. China
| | - Naveen Dandu
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108‐6050, USA, http://https://www.ndsu.edu/chemistry/people/faculty/sun.html
| | - Christopher McCleese
- Department of Chemistry, Case Western Reserve University, Cleveland, Ohio 44106, USA
| | - Yuhao Li
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108‐6050, USA, http://https://www.ndsu.edu/chemistry/people/faculty/sun.html
| | - Taotao Lu
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108‐6050, USA, http://https://www.ndsu.edu/chemistry/people/faculty/sun.html
| | - Hui Li
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108‐6050, USA, http://https://www.ndsu.edu/chemistry/people/faculty/sun.html
| | - Dillon Yost
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108‐6050, USA, http://https://www.ndsu.edu/chemistry/people/faculty/sun.html
| | - Chengzhe Wang
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108‐6050, USA, http://https://www.ndsu.edu/chemistry/people/faculty/sun.html
| | - Svetlana Kilina
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108‐6050, USA, http://https://www.ndsu.edu/chemistry/people/faculty/sun.html
| | - Clemens Burda
- Department of Chemistry, Case Western Reserve University, Cleveland, Ohio 44106, USA
| | - Wenfang Sun
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108‐6050, USA, http://https://www.ndsu.edu/chemistry/people/faculty/sun.html
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46
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Pei C, Cui P, McCleese C, Kilina S, Burda C, Sun W. Heteroleptic cationic iridium(III) complexes bearing naphthalimidyl substituents: synthesis, photophysics and reverse saturable absorption. Dalton Trans 2015; 44:2176-90. [PMID: 25512315 DOI: 10.1039/c4dt02384f] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Three heteroleptic cationic iridium(iii) complexes containing a cyclometalating 2-[3-(7-naphthalimidylfluoren-2'-yl)phenyl]pyridine ligand and different diimine (N^N) ligands (N^N = 2,2'-bipyridine (bpy, ), 1,10-phenanthroline (phen, ), and 5,5'-bis[7-(benzothiazol-2'-yl)fluoren-2'-yl]-2,2'-bipyridine (BTF-bpy, )) were synthesized and characterized. The photophysics of these complexes was systematically investigated via spectroscopic methods and by time-dependent density functional theory (TDDFT). All complexes possess a very weak charge-transfer tail at ca. 450-570 nm; and two intense absorption bands in the region of 290-350 nm and 350-450 nm, respectively. The emission of in CH2Cl2 emanates predominantly from the C^N ligand-localized (3)π,π* state. These emitting excited states also give rise to broadband triplet excited-state absorption in the visible to the near-IR region (i.e. 420-800 nm for and , and 460-800 nm for ). The kinetics of fs transient absorption (TA) reveals that the lowest singlet excited-state lifetimes of these complexes vary from 1.43 ps to 142 ps. The stronger excited-state absorption of compared to their respective ground-state absorption in the visible spectral range leads to strong reverse saturable absorption (RSA) at 532 nm for ns laser pulses. The trend of transmission signal decrease follows > > . Extending the π-conjugation of the N^N ligand increases the strength of RSA. In addition, the naphthalimidyl (NI) substitution at the cyclometalating ligand dramatically increases the triplet excited-state lifetimes and broadens the triplet excited-state absorption to the NIR region compared to the respective Ir(iii) complexes with a benzothiazolyl substituent on the cyclometalating ligand.
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Affiliation(s)
- Chengkui Pei
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108-6050, USA.
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47
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Affiliation(s)
- Svetlana Kilina
- Chemistry
and Biochemistry Department, North Dakota State University, Fargo, North Dakota 5810, United States
| | - Dmitri Kilin
- Department
of Chemistry, University of South Dakota, Vermillion, South Dakota 57069, United States
| | - Sergei Tretiak
- Theoretical
Division, Center for Nonlinear Studies (CNLS) and Center for Integrated
Nanotechnologies (CINT), Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
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48
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Makarov NS, Lau PC, Olson C, Velizhanin KA, Solntsev KM, Kieu K, Kilina S, Tretiak S, Norwood RA, Peyghambarian N, Perry JW. Two-photon absorption in CdSe colloidal quantum dots compared to organic molecules. ACS Nano 2014; 8:12572-12586. [PMID: 25427158 DOI: 10.1021/nn505428x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We discuss fundamental differences in electronic structure as reflected in one- and two-photon absorption spectra of semiconductor quantum dots and organic molecules by performing systematic experimental and theoretical studies of the size-dependent spectra of colloidal quantum dots. Quantum-chemical and effective-mass calculations are used to model the one- and two-photon absorption spectra and compare them with the experimental results. Currently, quantum-chemical calculations are limited to only small-sized quantum dots (nanoclusters) but allow one to study various environmental effects on the optical spectra such as solvation and various surface functionalizations. The effective-mass calculations, on the other hand, are applicable to the larger-sized quantum dots and can, in general, explain the observed trends but are insensitive to solvent and ligand effects. Careful comparison of the experimental and theoretical results allows for quantifying the range of applicability of theoretical methods used in this work. Our study shows that the small clusters can be in principle described in a manner similar to that used for organic molecules. In addition, there are several important factors (quality of passivation, nature of the ligands, and intraband/interband transitions) affecting optical properties of the nanoclusters. The larger-size quantum dots, on the other hand, behave similarly to bulk semiconductors, and can be well described in terms of the effective-mass models.
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Affiliation(s)
- Nikolay S Makarov
- School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics Georgia Institute of Technology , Atlanta, Georgia 30332, United States
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Kilina S, Cui P, Fischer SA, Tretiak S. Conditions for Directional Charge Transfer in CdSe Quantum Dots Functionalized by Ru(II) Polypyridine Complexes. J Phys Chem Lett 2014; 5:3565-3576. [PMID: 26278611 DOI: 10.1021/jz502017u] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Thermodynamic conditions governing the charge transfer direction in CdSe quantum dots (QD) functionalized by either Ru(II)-trisbipyridine or black dye are studied using density functional theory (DFT) and time-dependent DFT (TDDFT). Compared to the energy offsets of the isolated QD and the dye, QD-dye interactions strongly stabilize dye orbitals with respect to the QD states, while the surface chemistry of the QD has a minor effect on the energy offsets. In all considered QD/dye composites, the dyes always introduce unoccupied states close to the edge of the conduction band and control the electron transfer. Negatively charged ligands and less polar solvents significantly destabilize the dye's occupied orbitals shifting them toward the very edge of the valence band, thus, providing favorite conditions for the hole transfer. Overall, variations in the dye's ligands and solvent polarity can progressively adjust the electronic structure of QD/dye composites to modify conditions for the directed charge transfer.
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Affiliation(s)
- Svetlana Kilina
- †Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108, United States
| | - Peng Cui
- ‡Materials and Nanotechnology Program, North Dakota State University, Fargo, North Dakota 58108, United States
| | - Sean A Fischer
- §Department of Chemistry, University of Washington, Seattle, Washington 98195, United States
| | - Sergei Tretiak
- ∥Theoretical Division (T-1) and Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
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Li Y, Dandu N, Liu R, Kilina S, Sun W. Synthesis and photophysics of reverse saturable absorbing heteroleptic iridium(iii) complexes bearing 2-(7-R-fluoren-2′-yl)pyridine ligands. Dalton Trans 2014; 43:1724-35. [DOI: 10.1039/c3dt52184b] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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