1
|
Liu L, Liu X, Kurganskii I, Chen X, Gurzadyan GG, Zhao J, Wan Y, Fedin M. Charge Transfer and Intersystem Crossing in Compact Naphthalenediimide-Phenothiazine Triads: Synthesis and Study of the Photophysical Property with Transient Optical and Electron Paramagnetic Resonance Spectroscopic Methods. J Phys Chem B 2024; 128:7237-7253. [PMID: 39016740 DOI: 10.1021/acs.jpcb.4c03145] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/18/2024]
Abstract
In order to obtain a long-lived charge separation (CS) state in compact electron donor-acceptor molecular systems, we prepared a series of naphthalenediimide (NDI)-phenothiazine (PTZ) triads, with phenylene as the linker between the donor and acceptor. Conformation restriction is imposed to control the mutual orientation of the NDI and PTZ units by attaching methyl groups on the phenylene linker to tune the electronic coupling between the donor and the acceptor. Moreover, the PTZ moiety was oxidized to sulfoxide to tune the ordering of the CS state and the 3LE state (LE: locally excited state). UV-vis absorption spectra indicate electronic coupling between NDI with the phenylene linker as well as the PTZ units, manifested by the appearance of a charge-transfer (CT) absorption band, whereas this coupling is devoid in the triads with conformation restriction imposed. Fluorescence is strongly quenched in the triads compared to the reference compound, indicating electron transfer upon photoexcitation. Femtosecond transient absorption spectra indicate that the CS takes 0.8 ps, and then the 3LE state is formed by charge recombination in 83 ps. Nanosecond transient absorption (ns-TA) spectra show that the 3NDI state was observed in nonpolar solvents such as cyclohexane (triplet state lifetime: 95.7 μs), whereas the CS state was observed in more polar solvents. The CS state lifetimes are up to 1.2 μs (in toluene). Time-resolved electron paramagnetic resonance spectra of the triads in toluene consist of two types of signals: CS states (narrower signals, ∼10 mT) and 3LE states (broader signals, ∼50 to 200 mT). In the spectra of the triads containing PTZ, the CS state signals dominate, whereas for the triads containing oxidized PTZ, the 3NDI signals (zero-field splitting D ≈ 2000 MHz) prevail, both observations being in agreement with the ns-TA spectral studies. The electron spin polarization phase pattern of the 3NDI states of the triads indicates that the intersystem crossing (ISC) mechanism is spin-orbit charge-transfer ISC. Considering the 3CS state as ion pairs, the electron-exchange energy (J) is determined to be -39 to -59 MHz, and the electron spin dipolar interaction is 83-92 MHz.
Collapse
Affiliation(s)
- Lezhang Liu
- State Key Laboratory of Fine Chemicals, Frontier Science Center for Smart Materials, School of Chemical Engineering, Dalian University of Technology, Dalian 116024, P. R. China
| | - Xi Liu
- College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
| | - Ivan Kurganskii
- International Tomography Center, SB RAS, Institutskaya Street, 3A, Novosibirsk 630090, Russia
| | - Xi Chen
- State Key Laboratory of Fine Chemicals, Frontier Science Center for Smart Materials, School of Chemical Engineering, Dalian University of Technology, Dalian 116024, P. R. China
| | - Gagik G Gurzadyan
- State Key Laboratory of Fine Chemicals, Institute of Artificial Photosynthesis, Dalian University of Technology, Dalian 116024, P. R. China
| | - Jianzhang Zhao
- State Key Laboratory of Fine Chemicals, Frontier Science Center for Smart Materials, School of Chemical Engineering, Dalian University of Technology, Dalian 116024, P. R. China
| | - Yan Wan
- College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
| | - Matvey Fedin
- International Tomography Center, SB RAS, Institutskaya Street, 3A, Novosibirsk 630090, Russia
- Novosibirsk State University, Pirogova Street 2, Novosibirsk 630090, Russia
| |
Collapse
|
2
|
Chen X, Sun L, Sukhanov AA, Doria S, Bussotti L, Zhao J, Xu H, Dick B, Voronkova VK, Di Donato M. Photophysics and photochemistry of thermally activated delayed fluorescence emitters based on the multiple resonance effect: transient optical and electron paramagnetic resonance studies. Chem Sci 2024; 15:10867-10881. [PMID: 39027280 PMCID: PMC11253189 DOI: 10.1039/d4sc02513j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2024] [Accepted: 05/31/2024] [Indexed: 07/20/2024] Open
Abstract
The photochemistry of two representative thermally activated delayed fluorescence (TADF) emitters based on the multiple resonance effect (MRE) (DABNA-1 and DtBuCzB) was studied. No significant TADF was observed in fluid solution, although the compounds have a long-lived triplet state (ca. 30 μs). We found that these planar boron molecules bind with Lewis bases, e.g., 4-dimethylaminopyridine (DMAP) or an N-heterocyclic carbene (NHC). A new blue-shifted absorption band centered at 368 nm was observed for DtBuCzB upon formation of the adduct; however, the fluorescence of the adduct is the same as that of the free DtBuCzB. We propose that photo-dissociation occurs for the DtBuCzB-DMAP adduct, which is confirmed by femtosecond transient absorption spectra, implying that fluorescence originates from DtBuCzB produced by photo-dissociation; the subsequent in situ re-binding was observed with nanosecdon transient absorption spectroscopy. No photo-dissociation was observed for the NHC adduct. Time-resolved electron paramagnetic resonance (TREPR) spectra show that the triplet states of DABNA-1 and DtBuCzB have similar zero field splitting (ZFS) parameters (D = 1450 MHz). Theoretical studies show that the slow ISC is due to small SOC and weak Herzberg-Teller coupling, although the S1/T1 energy gap is small (0.14 eV), which rationalizes the lack of TADF.
Collapse
Affiliation(s)
- Xi Chen
- State Key Laboratory of Fine Chemicals, Frontier Science Center for Smart Materials, School of Chemical Engineering, Dalian University of Technology Dalian 116024 P. R. China
| | - Lei Sun
- Jiangsu Co-Innovation Center of Efficient Processing and Utilization of Forest Resources, Key Laboratory of Forestry Genetics & Biotechnology of Ministry of Education, Jiangsu Provincial Key Lab for the Chemistry and Utilization of Agro-Forest Biomass, College of Chemical Engineering, Nanjing Forestry University Nanjing 210037 P. R. China
- School of Chemistry and Chemical Engineering, Henan Normal University Xinxiang 453002 China
| | - Andrey A Sukhanov
- Zavoisky Physical-Technical Institute, FRC Kazan Scientific Center of RAS Kazan 420029 Russia
| | - Sandra Doria
- LENS (European Laboratory for Non-Linear Spectroscopy) Via N. Carrara 1 50019 Sesto Fiorentino (FI) Italy
- ICCOM-CNR Via Madonna del Piano 10-12 50019 Sesto Fiorentino (FI) Italy
| | - Laura Bussotti
- LENS (European Laboratory for Non-Linear Spectroscopy) Via N. Carrara 1 50019 Sesto Fiorentino (FI) Italy
| | - Jianzhang Zhao
- State Key Laboratory of Fine Chemicals, Frontier Science Center for Smart Materials, School of Chemical Engineering, Dalian University of Technology Dalian 116024 P. R. China
| | - Haijun Xu
- Jiangsu Co-Innovation Center of Efficient Processing and Utilization of Forest Resources, Key Laboratory of Forestry Genetics & Biotechnology of Ministry of Education, Jiangsu Provincial Key Lab for the Chemistry and Utilization of Agro-Forest Biomass, College of Chemical Engineering, Nanjing Forestry University Nanjing 210037 P. R. China
- School of Chemistry and Chemical Engineering, Henan Normal University Xinxiang 453002 China
| | - Bernhard Dick
- Lehrstuhl für Physikalische Chemie, Institut für Physikalische und Theoretische Chemie, Universität Regensburg Regensburg 93053 Germany
| | - Violeta K Voronkova
- Zavoisky Physical-Technical Institute, FRC Kazan Scientific Center of RAS Kazan 420029 Russia
| | - Mariangela Di Donato
- LENS (European Laboratory for Non-Linear Spectroscopy) Via N. Carrara 1 50019 Sesto Fiorentino (FI) Italy
- ICCOM-CNR Via Madonna del Piano 10-12 50019 Sesto Fiorentino (FI) Italy
| |
Collapse
|
3
|
Zhang X, Chen X, Sun Y, Zhao J. Radical enhanced intersystem crossing mechanism, electron spin dynamics of high spin states and their applications in the design of heavy atom-free triplet photosensitizers. Org Biomol Chem 2024; 22:5257-5283. [PMID: 38884590 DOI: 10.1039/d4ob00520a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/18/2024]
Abstract
Heavy atom-free triplet photosensitizers (PSs) can overcome the high cost and biological toxicity of traditional molecular systems containing heavy atoms (such as Pt(II), Ir(III), Ru(II), Pd(II), Lu(III), I, or Br atoms) and, therefore, are developing rapidly. Connecting a stable free radical to the chromophore can promote the intersystem crossing (ISC) process through electron spin exchange interaction to produce the triplet state of the chromophore or the doublet (D) and quartet (Q) states when taking the whole spin system into account. These molecular systems based on the radical enhanced ISC (REISC) mechanism are important in the field of heavy atom-free triplet PSs. The REISC system has a simple molecular structure and good biocompatibility, and it is especially helpful for building high-spin quantum states (D and Q states) that have the potential to be developed as qubits in quantum information science. This review introduces the molecular structure design for the purpose of high-spin states. Time-resolved electron paramagnetic resonance (TREPR) is the most important characterization method to reveal the properties of these molecular systems, generation mechanism and electron spin polarization (ESP) of the high spin states. The spin polarization manipulation of high spin states and potential application in the field of quantum information engineering are also summarized. Moreover, molecular design principles of the REISC system to obtain long absorption wavelength, high triplet state quantum yield and long triplet state lifetime are introduced, as well as applications of the compounds in triplet-triplet annihilation upconversion, photodynamic therapy and bioimaging. This review is useful for the design of heavy atom-free triplet PSs based on the radical-chromophore molecular structure motif and the study of the photophysics of the compounds, as well as the electron spin dynamics of the multi electron system upon photoexcitation.
Collapse
Affiliation(s)
- Xue Zhang
- State Key Laboratory of Fine Chemicals, Frontiers Science Centre for Smart Materials, School of Chemical Engineering, Dalian University of Technology, Dalian 116024, P. R. China.
| | - Xi Chen
- State Key Laboratory of Fine Chemicals, Frontiers Science Centre for Smart Materials, School of Chemical Engineering, Dalian University of Technology, Dalian 116024, P. R. China.
| | - Yue Sun
- State Key Laboratory of Fine Chemicals, Frontiers Science Centre for Smart Materials, School of Chemical Engineering, Dalian University of Technology, Dalian 116024, P. R. China.
| | - Jianzhang Zhao
- State Key Laboratory of Fine Chemicals, Frontiers Science Centre for Smart Materials, School of Chemical Engineering, Dalian University of Technology, Dalian 116024, P. R. China.
| |
Collapse
|
4
|
Shi Y, Zhang Y, Wang Z, Yuan T, Meng T, Li Y, Li X, Yuan F, Tan Z, Fan L. Onion-like multicolor thermally activated delayed fluorescent carbon quantum dots for efficient electroluminescent light-emitting diodes. Nat Commun 2024; 15:3043. [PMID: 38589394 PMCID: PMC11001924 DOI: 10.1038/s41467-024-47372-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2023] [Accepted: 03/27/2024] [Indexed: 04/10/2024] Open
Abstract
Carbon quantum dots are emerging as promising nanomaterials for next-generation displays. The elaborate structural design is crucial for achieving thermally activated delayed fluorescence, particularly for improving external quantum efficiency of electroluminescent light-emitting diodes. Here, we report the synthesis of onion-like multicolor thermally activated delayed fluorescence carbon quantum dots with quantum yields of 42.3-61.0%. Structural, spectroscopic characterization and computational studies reveal that onion-like structures assembled from monomer carbon quantum dots of different sizes account for the decreased singlet-triplet energy gap, thereby achieving efficient multicolor thermally activated delayed fluorescence. The devices exhibit maximum luminances of 3785-7550 cd m-2 and maximum external quantum efficiency of 6.0-9.9%. Importantly, owing to the weak van der Waals interactions and adequate solution processability, flexible devices with a maximum luminance of 2554 cd m-2 are realized. These findings facilitate the development of high-performance carbon quantum dots-based electroluminescent light-emitting diodes that are promising for practical applications.
Collapse
Affiliation(s)
- Yuxin Shi
- Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, College of Chemistry, Beijing Normal University, Beijing, 100875, China
| | - Yang Zhang
- Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, College of Chemistry, Beijing Normal University, Beijing, 100875, China.
| | - Zhibin Wang
- College of Physics and Energy, Fujian Normal University, Fuzhou, 350117, China
| | - Ting Yuan
- Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, College of Chemistry, Beijing Normal University, Beijing, 100875, China
| | - Ting Meng
- Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, College of Chemistry, Beijing Normal University, Beijing, 100875, China
| | - Yunchao Li
- Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, College of Chemistry, Beijing Normal University, Beijing, 100875, China
| | - Xiaohong Li
- Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, College of Chemistry, Beijing Normal University, Beijing, 100875, China
| | - Fanglong Yuan
- Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, College of Chemistry, Beijing Normal University, Beijing, 100875, China.
| | - Zhan'ao Tan
- Beijing Advanced Innovation Centre for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing, 100029, China.
| | - Louzhen Fan
- Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, College of Chemistry, Beijing Normal University, Beijing, 100875, China.
| |
Collapse
|
5
|
Franca L, Danos A, Saxena R, Kuila S, Stavrou K, Li C, Wedler S, Köhler A, Monkman AP. Exploring the Early Time Behavior of the Excited States of an Archetype Thermally Activated Delayed Fluorescence Molecule. J Phys Chem Lett 2024; 15:1734-1740. [PMID: 38323906 PMCID: PMC10875657 DOI: 10.1021/acs.jpclett.4c00030] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2024] [Revised: 01/30/2024] [Accepted: 02/02/2024] [Indexed: 02/08/2024]
Abstract
Optical pump-probe techniques allow for an in-depth study of dark excited states. Here, we utilize them to map and gain insights into the excited states involved in the thermally activated delayed fluorescence (TADF) mechanism of a benchmark TADF emitter DMAC-TRZ. The results identify different electronic excited states involved in the key TADF transitions and their nature by combining pump-probe and photoluminescence measurements. The photoinduced absorption signals are highly dependent on polarity, affecting the transition oscillator strength but not their relative energy positions. In methylcyclohexane, a strong and vibronically structured local triplet excited state absorption (3LE → 3LEn) is observed, which is quenched in higher polarity solvents as 3CT becomes the lowest triplet state. Furthermore, ultrafast transient absorption (fsTA) confirms the presence of two stable conformers of DMAC-TRZ: (1) quasi-axial (QA) interconverting within 20 ps into (2) quasi-equatorial (QE) in the excited state. Moreover, fsTA highlights how sensitive excited state couplings are to the environment and the molecular conformation.
Collapse
Affiliation(s)
- Larissa
G. Franca
- Department
of Physics, Durham University, South Road, Durham DH13LE, United Kingdom
| | - Andrew Danos
- Department
of Physics, Durham University, South Road, Durham DH13LE, United Kingdom
| | - Rishabh Saxena
- Soft
Matter Optoelectronics and Bavarian Polymer Institute (BPS), University of Bayreuth, Universitätsstrasse 30, Bayreuth 95440, Germany
| | - Suman Kuila
- Department
of Physics, Durham University, South Road, Durham DH13LE, United Kingdom
| | - Kleitos Stavrou
- Department
of Physics, Durham University, South Road, Durham DH13LE, United Kingdom
| | - Chunyong Li
- Department
of Physics, Durham University, South Road, Durham DH13LE, United Kingdom
| | - Stefan Wedler
- Soft
Matter Optoelectronics and Bavarian Polymer Institute (BPS), University of Bayreuth, Universitätsstrasse 30, Bayreuth 95440, Germany
| | - Anna Köhler
- Soft
Matter Optoelectronics and Bavarian Polymer Institute (BPS), University of Bayreuth, Universitätsstrasse 30, Bayreuth 95440, Germany
| | - Andrew P. Monkman
- Department
of Physics, Durham University, South Road, Durham DH13LE, United Kingdom
| |
Collapse
|
6
|
Wu CC, Tsai YX, Chu LK, Chen IC. Investigation of Electronic Structures of Triplet States Using Step-Scan Time-Resolved Fourier-Transform Near-Infrared Spectroscopy. J Phys Chem Lett 2024; 15:912-918. [PMID: 38241171 PMCID: PMC10839901 DOI: 10.1021/acs.jpclett.3c03521] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Revised: 01/08/2024] [Accepted: 01/11/2024] [Indexed: 01/21/2024]
Abstract
Triplet transitions of light-emitting materials, including rose bengal, tris(2-phenylpyridine)iridium(III) [Ir(ppy)3], tris(1-phenylisoquinoline)iridium(III) [Ir(piq)3], and bis[2-(4,6-difluorophenyl)pyridinato-C2,N](picolinato)iridium(III) (FIrpic), were studied using step-scan time-resolved Fourier-transform near-infrared spectroscopy. The samples were excited to their singlet excited states by a 355 nm laser and then underwent efficient conversions/crossings to their triplet manifolds. For rose bengal, a transient absorption band appeared at 9400 cm-1, attributed to the T3 ← T1 transition based on the corresponding time evolution and the theoretical calculations. For Ir(ppy)3, Ir(piq)3, and FIrpic, the most intense bands were observed at 7700, 7500, and 7500 cm-1 and assigned to T7 ← T1, T6 ← T1, and T6 ← T1 transitions, respectively. For Ir(ppy)3, the most intense band involved transitions between different triplet metal-to-ligand charge transfer (3MLCT) states, while for Ir(piq)3 and FIrpic, they involved a metal center to 3MLCT transition. These T1 states were assigned to 3MLCT.
Collapse
Affiliation(s)
- Chia Chun Wu
- Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan 300044, Republic
of China
| | - Yu-Xiang Tsai
- Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan 300044, Republic
of China
| | - Li-Kang Chu
- Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan 300044, Republic
of China
| | - I-Chia Chen
- Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan 300044, Republic
of China
| |
Collapse
|
7
|
Wu Y, Cao H, Bakirov MM, Sukhanov AA, Li J, Liao S, Xiao X, Zhao J, Li MD, Kandrashkin YE. A Rational Way to Control the Triplet State Wave Function Confinement of Organic Chromophores: Effect of the Connection Sites and Spin Density Distribution-Guided Molecular Structure Design Principles in Bodipy Dimers. J Phys Chem Lett 2024; 15:959-968. [PMID: 38252167 DOI: 10.1021/acs.jpclett.3c03225] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2024]
Abstract
To study the intersystem crossing (ISC) and the spatial confinement of the triplet excited states of organic chromophores, we prepared a series of Bodipy dimers. We found that the connection position of the two units has a significant effect on the absorption and fluorescence. Singlet oxygen quantum yields of 3.8-12.4% were observed for the dimers, which are independent of solvent polarity. Nanosecond transient absorption spectra indicate the population of long-lived triplet excited states with lifetimes (τT) of 45-454 μs. Pulsed laser-excited time-resolved electron paramagnetic resonance (TREPR) spectra show that the T1 triplet states are essentially delocalized, which is different from the case for the previously reported Bodipy dimers. The TREPR spectra of the triplet states imply that the delocalization over the whole dimer essentially depends on the electron density of the carbon atoms at the connection sites. This property may become a universal rule for controlling the T1 state confinement in multichromophore organic molecules.
Collapse
Affiliation(s)
- Yanran Wu
- State Key Laboratory of Fine Chemicals, Frontiers Science Center for Smart Materials, School of Chemical Engineering, Dalian University of Technology, Dalian 116024, P. R. China
| | - Huaiman Cao
- State Key Laboratory of Fine Chemicals, Frontiers Science Center for Smart Materials, School of Chemical Engineering, Dalian University of Technology, Dalian 116024, P. R. China
| | - Marcel M Bakirov
- Zavoisky Physical-Technical Institute, FRC Kazan Scientific Center of Russian Academy of Sciences, Kazan 420029, Russia
| | - Andrey A Sukhanov
- Zavoisky Physical-Technical Institute, FRC Kazan Scientific Center of Russian Academy of Sciences, Kazan 420029, Russia
| | - Jiayu Li
- Department of Chemistry and Key Laboratory for Preparation and Application of Ordered Structural Materials of Guangdong Province, Shantou University, Shantou 515063, P. R. China
| | - Sheng Liao
- Department of Chemistry and Key Laboratory for Preparation and Application of Ordered Structural Materials of Guangdong Province, Shantou University, Shantou 515063, P. R. China
| | - Xiao Xiao
- State Key Laboratory of Fine Chemicals, Frontiers Science Center for Smart Materials, School of Chemical Engineering, Dalian University of Technology, Dalian 116024, P. R. China
| | - Jianzhang Zhao
- State Key Laboratory of Fine Chemicals, Frontiers Science Center for Smart Materials, School of Chemical Engineering, Dalian University of Technology, Dalian 116024, P. R. China
- State Key Laboratory of Chemistry and Utilization of Carbon Based Energy Resources, College of Chemistry, Xinjiang University, Urumqi 830017, P. R. China
| | - Ming-De Li
- Department of Chemistry and Key Laboratory for Preparation and Application of Ordered Structural Materials of Guangdong Province, Shantou University, Shantou 515063, P. R. China
| | - Yuri E Kandrashkin
- Zavoisky Physical-Technical Institute, FRC Kazan Scientific Center of Russian Academy of Sciences, Kazan 420029, Russia
| |
Collapse
|
8
|
Palion-Gazda J, Choroba K, Penkala M, Rawicka P, Machura B. Further Insights into the Impact of Ligand-Localized Excited States on the Photophysics of Phenanthroline-Based Rhenium(I) Tricarbonyl Complexes. Inorg Chem 2024; 63:1356-1366. [PMID: 38155540 DOI: 10.1021/acs.inorgchem.3c03894] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2023]
Abstract
The present work shows the pivotal role of N-donor substituents attached to 1,10-phenanthroline at the 4,7-positions in perturbation of ground- and excited-state properties of fac-[ReCl(CO)3(R2phen)]. Excited-state processes occurring upon photoexcitation in the designed systems were thoroughly explored with a wide range of steady-state and time-resolved spectroscopic techniques, including transient absorption, as well as experimental results were complemented by theoretical studies based on the density functional theory (DFT). It was demonstrated that the attachment of six-membered heterocyclic amines (piperidine─ppr, morpholine─mor, and thiomorpholine─tmor) is a very effective tool for extending absorptivity and excited-state lifetimes of resulting fac-[ReCl(CO)3(R2phen)] due to the contribution of the excited state localized on the phenanthroline-based ligand. Both absorption and emission properties of these systems were attributed to configurationally mixed MLCT/IL excited states. Re(I) complexes with phenoxazine (pxz) and phenothiazine (ptz) substituents were shown to possess charge-separated excited states, clearly evidenced by the simultaneous presence of signals typical of phen-* and pxz+* or ptz+* in transient absorption spectra. Both complexes are rare examples of NIR light-emitting coordination compounds. The decoration of the phen framework with less polar 9,9-dimethyl-9,10-dihydroacridine (dmac) groups resulted in the formation of [ReCl(CO)3(R2phen)] with mixed 3MLCT/3ILCT triplet excited state.
Collapse
Affiliation(s)
- Joanna Palion-Gazda
- Institute of Chemistry, Faculty of Science and Technology, University of Silesia, Szkolna 9, 40-006 Katowice, Poland
| | - Katarzyna Choroba
- Institute of Chemistry, Faculty of Science and Technology, University of Silesia, Szkolna 9, 40-006 Katowice, Poland
| | - Mateusz Penkala
- Institute of Chemistry, Faculty of Science and Technology, University of Silesia, Szkolna 9, 40-006 Katowice, Poland
| | - Patrycja Rawicka
- Institute of Physics, Faculty of Science and Technology, University of Silesia in Katowice, 75 Pułku Piechoty 1a, 41-500 Chorzów, Poland
| | - Barbara Machura
- Institute of Chemistry, Faculty of Science and Technology, University of Silesia, Szkolna 9, 40-006 Katowice, Poland
| |
Collapse
|
9
|
Xiao X, Mu T, Sukhanov AA, Zhou Y, Yu P, Yu F, Elmali A, Zhao J, Karatay A, Voronkova VK. The effect of thionation of the carbonyl group on the photophysics of compact spiro rhodamine-naphthalimide electron donor-acceptor dyads: intersystem crossing, charge separation, and electron spin dynamics. Phys Chem Chem Phys 2023; 25:31667-31682. [PMID: 37966808 DOI: 10.1039/d3cp04891h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2023]
Abstract
Herein, a spiro rhodamine (Rho)-thionated naphthalimide (NIS) electron donor-acceptor orthogonal dyad (Rho-NIS) was prepared to study the formation of a long-lived charge separation (CS) state via the electron spin control approach. The transient absorption (TA) spectra of Rho-NIS indicated that the intersystem crossing (ISC) occurs within 7-42 ps to produce the 3NIS state via the spin orbit coupling ISC (SOC-ISC). The energy order of 3CS (2.01 eV in n-hexane, HEX) and 3LE states (1.68 eV in HEX) depended on the solvent polarity. The 3NIS state having n-π* character and a lifetime of 0.38 μs was observed for Rho-NIS in toluene (TOL). Alternatively, in acetonitrile (ACN), the long-lived 3CS state (0.21 μs) with a high CS state quantum yield (ΦCS, 97%) was produced with the 3NIS state as the precursor and the CS took 134 ps. On the contrary, in the case of the reference Rho-naphthalimide (NI) Rho-NI dyad without thionation of its carbonyl group, a long-lived CS state (0.94 μs) with a high energy level (ECS = 2.12 eV) was generated even in HEX with a lower ΦCS (49%). In the presence of an acid, the Rho unit in the Rho-NIS adopted an open form (Rho-o) and the 3NIS state was produced within 24-47 ps with the 1Rho-o state as the precursor. Subsequently, slow intramolecular triplet-triplet energy transfer (TTET, 0.11-0.60 μs) produced the 3Rho-o state (9.4-13.6 μs). According to the time-resolved electron paramagnetic resonance (TREPR) spectra of NIS-NH2, the zero-field splitting (ZFS) parameter |D| and E of the triplet state were determined to be 6165 MHz and -1233 MHz, respectively, indicating that its triplet state has significant nπ* character, which was supported by its short triplet state lifetime (6.1 μs).
Collapse
Affiliation(s)
- Xiao Xiao
- State Key Laboratory of Fine Chemicals, Frontier Science Center for Smart Materials, School of Chemical Engineering, Dalian University of Technology, 2 Ling Gong Rd., Dalian 116024, P. R. China.
| | - Tong Mu
- State Key Laboratory of Fine Chemicals, Frontier Science Center for Smart Materials, School of Chemical Engineering, Dalian University of Technology, 2 Ling Gong Rd., Dalian 116024, P. R. China.
| | - Andrey A Sukhanov
- Zavoisky Physical-Technical Institute FRC Kazan Scientific Center of RAS, Sibirsky Tract 10/7, Kazan 420029, Russia.
| | - Yihang Zhou
- State Key Laboratory of Fine Chemicals, Frontier Science Center for Smart Materials, School of Chemical Engineering, Dalian University of Technology, 2 Ling Gong Rd., Dalian 116024, P. R. China.
| | - Peiran Yu
- State Key Laboratory of Fine Chemicals, Frontier Science Center for Smart Materials, School of Chemical Engineering, Dalian University of Technology, 2 Ling Gong Rd., Dalian 116024, P. R. China.
| | - Fabiao Yu
- Key Laboratory of Hainan Trauma and Disaster Rescue, The First Affiliated Hospital of Hainan Medical University, Hainan Medical University, Haikou 571199, P. R. China
| | - Ayhan Elmali
- Department of Engineering Physics, Faculty of Engineering, Ankara University, 06100, Ankara, Turkey.
| | - Jianzhang Zhao
- State Key Laboratory of Fine Chemicals, Frontier Science Center for Smart Materials, School of Chemical Engineering, Dalian University of Technology, 2 Ling Gong Rd., Dalian 116024, P. R. China.
| | - Ahmet Karatay
- Department of Engineering Physics, Faculty of Engineering, Ankara University, 06100, Ankara, Turkey.
| | - Violeta K Voronkova
- Zavoisky Physical-Technical Institute FRC Kazan Scientific Center of RAS, Sibirsky Tract 10/7, Kazan 420029, Russia.
| |
Collapse
|
10
|
Cao L, Liu X, Zhang X, Zhao J, Yu F, Wan Y. The effect of dark states on the intersystem crossing and thermally activated delayed fluorescence of naphthalimide-phenothiazine dyads. Beilstein J Org Chem 2023; 19:1028-1046. [PMID: 37497052 PMCID: PMC10366440 DOI: 10.3762/bjoc.19.79] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Accepted: 07/07/2023] [Indexed: 07/28/2023] Open
Abstract
A series of 1,8-naphthalimide (NI)-phenothiazine (PTZ) electron donor-acceptor dyads were prepared to study the thermally activated delayed fluorescence (TADF) properties of the dyads, from a point of view of detection of the various transient species. The photophysical properties of the dyads were tuned by changing the electron-donating and the electron-withdrawing capability of the PTZ and NI moieties, respectively, by oxidation of the PTZ unit, or by using different aryl substituents attached to the NI unit. This tuning effect was manifested in the UV-vis absorption and fluorescence emission spectra, e.g., in the change of the charge transfer absorption bands. TADF was observed for the dyads containing the native PTZ unit, and the prompt and delayed fluorescence lifetimes changed with different aryl substituents on the imide part. In polar solvents, no TADF was observed. For the dyads with the PTZ unit oxidized, no TADF was observed as well. Femtosecond transient absorption spectra showed that the charge separation takes ca. 0.6 ps, and admixtures of locally excited (3LE) state and charge separated (1CS/3CS) states formed (in n-hexane). The subsequent charge recombination from the 1CS state takes ca. 7.92 ns. Upon oxidation of the PTZ unit, the beginning of charge separation is at 178 fs and formation of 3LE state takes 4.53 ns. Nanosecond transient absorption (ns-TA) spectra showed that both 3CS and 3LE states were observed for the dyads showing TADF, whereas only 3LE or 3CS states were observed for the systems lacking TADF. This is a rare but unambiguous experimental evidence that the spin-vibronic coupling of 3CS/3LE states is crucial for TADF. Without the mediating effect of the 3LE state, no TADF is resulted, even if the long-lived 3CS state is populated (lifetime τCS ≈ 140 ns). This experimental result confirms the 3CS → 1CS reverse intersystem crossing (rISC) is slow, without coupling with an approximate 3LE state. These studies are useful for an in-depth understanding of the photophysical mechanisms of the TADF emitters, as well as for molecular structure design of new electron donor-acceptor TADF emitters.
Collapse
Affiliation(s)
- Liyuan Cao
- State Key Laboratory of Fine Chemicals, Frontier Science Center for Smart Materials, School of Chemical Engineering, Dalian University of Technology, 2 Ling Gong Road, Dalian, 116024, P. R. China
| | - Xi Liu
- College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
| | - Xue Zhang
- State Key Laboratory of Fine Chemicals, Frontier Science Center for Smart Materials, School of Chemical Engineering, Dalian University of Technology, 2 Ling Gong Road, Dalian, 116024, P. R. China
| | - Jianzhang Zhao
- State Key Laboratory of Fine Chemicals, Frontier Science Center for Smart Materials, School of Chemical Engineering, Dalian University of Technology, 2 Ling Gong Road, Dalian, 116024, P. R. China
| | - Fabiao Yu
- Key Laboratory of Hainan Trauma and Disaster Rescue, The First Affiliated Hospital of Hainan Medical University, Hainan Medical University, Haikou 571199, P. R. China
| | - Yan Wan
- College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
| |
Collapse
|