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Ikeshita M, Hara N, Imai Y, Naota T. Chiroptical Response Control of Planar and Axially Chiral Polymethylene-Vaulted Platinum(II) Complexes Bearing 1,1'-Binaphthyl Frameworks. Inorg Chem 2023; 62:13964-13976. [PMID: 37581577 DOI: 10.1021/acs.inorgchem.3c01935] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/16/2023]
Abstract
In this study, the synthesis, structure, and chiroptical response control of planar chiral polymethylene-vaulted trans-bis[(β-iminomethyl)aryloxy]platinum(II) complexes bearing axially chiral 1,1'-binaphthyl ligands are described. A series of enantiopure polymethylene (n = 4-10)-vaulted complexes were prepared in 6 steps using commercially available (R)- or (S)-BINOL as the starting material without an optical resolution process. The trans-coordination and three-dimensional vaulted structures of the platinum complexes were elucidated from X-ray diffraction (XRD) studies. The complexes were found to show structural dependence of chiroptical responses in the dilute solution state such that the absolute values of [α]D, dissymmetry factors gabs in circular dichroism (CD), and glum in circularly polarized luminescence (CPL) increased upon shortening the length of the polymethylene bridges. The enhanced chiroptical responses were theoretically investigated using density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations, and the results are discussed in terms of the molecular structures and transition dipole moments of the ground states. The structural dependence of the chiroptical responses was ascribed to the distortion of the coordination platforms caused by restriction of the vaulting methylene linkers.
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Affiliation(s)
- Masahiro Ikeshita
- Department of Chemistry, Graduate School of Engineering Science, Osaka University, Machikaneyama, Toyonaka, Osaka 560-8531, Japan
- Department of Applied Molecular Chemistry, College of Industrial Technology, Nihon University, Narashino, Chiba 275-8575, Japan
| | - Nobuyuki Hara
- Department of Applied Chemistry, Faculty of Science and Engineering, Kindai University, 3-4-1 Kowakae, Higashi-Osaka, Osaka 577-8502, Japan
| | - Yoshitane Imai
- Department of Applied Chemistry, Faculty of Science and Engineering, Kindai University, 3-4-1 Kowakae, Higashi-Osaka, Osaka 577-8502, Japan
| | - Takeshi Naota
- Department of Chemistry, Graduate School of Engineering Science, Osaka University, Machikaneyama, Toyonaka, Osaka 560-8531, Japan
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Muthig AMT, Mrózek O, Ferschke T, Rödel M, Ewald B, Kuhnt J, Lenczyk C, Pflaum J, Steffen A. Mechano-Stimulus and Environment-Dependent Circularly Polarized TADF in Chiral Copper(I) Complexes and Their Application in OLEDs. J Am Chem Soc 2023; 145:4438-4449. [PMID: 36795037 DOI: 10.1021/jacs.2c09458] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
Abstract
Molecular emitters that combine circularly polarized luminescence (CPL) and high radiative rate constants of the triplet exciton decay are highly attractive for electroluminescent devices (OLEDs) or next-generation photonic applications, such as spintronics, quantum computing, cryptography, or sensors. However, the design of such emitters is a major challenge because the criteria for enhancing these two properties are mutually exclusive. In this contribution, we show that enantiomerically pure {Cu(CbzR)[(S/R)-BINAP]} [R = H (1), 3,6-tBu (2)] are efficient thermally activated delayed fluorescence (TADF) emitters with high radiative rate constants of kTADF up to 3.1 × 105 s-1 from 1/3LLCT states according to our temperature-dependent time-resolved luminescence studies. The efficiency of the TADF process and emission wavelengths are highly sensitive to environmental hydrogen bonding of the ligands, which can be disrupted by grinding of the crystalline materials. The origin of this pronounced mechano-stimulus photophysical behavior is a thermal equilibrium between the 1/3LLCT states and a 3LC state of the BINAP ligand, which depends on the relative energetic order of the excited states and is prone to inter-ligand C-H···π interactions. The copper(I) complexes are also efficient CPL emitters displaying exceptional dissymmetry values glum of up to ±0.6 × 10-2 in THF solution and ±2.1 × 10-2 in the solid state. Importantly for application in electroluminescence devices, the C-H···π interactions can also be disrupted by employing sterically bulky matrices. Accordingly, we have investigated various matrix materials for successful implementation of the chiral copper(I) TADF emitters in proof-of-concept CP-OLEDs.
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Affiliation(s)
- André Martin Thomas Muthig
- Department of Chemistry and Chemical Biology, TU Dortmund University, Otto-Hahn-Str. 6, 44227 Dortmund, Germany
| | - Ondřej Mrózek
- Department of Chemistry and Chemical Biology, TU Dortmund University, Otto-Hahn-Str. 6, 44227 Dortmund, Germany
| | - Thomas Ferschke
- Experimental Physics VI, Julius-Maximilian University, Am Hubland, 97074 Würzburg, Germany
| | - Maximilian Rödel
- Experimental Physics VI, Julius-Maximilian University, Am Hubland, 97074 Würzburg, Germany
| | - Björn Ewald
- Experimental Physics VI, Julius-Maximilian University, Am Hubland, 97074 Würzburg, Germany
| | - Julia Kuhnt
- Department of Chemistry and Chemical Biology, TU Dortmund University, Otto-Hahn-Str. 6, 44227 Dortmund, Germany
| | - Carsten Lenczyk
- Department of Chemistry and Chemical Biology, TU Dortmund University, Otto-Hahn-Str. 6, 44227 Dortmund, Germany
| | - Jens Pflaum
- Experimental Physics VI, Julius-Maximilian University, Am Hubland, 97074 Würzburg, Germany
| | - Andreas Steffen
- Department of Chemistry and Chemical Biology, TU Dortmund University, Otto-Hahn-Str. 6, 44227 Dortmund, Germany
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Oelschlegel M, Hua SA, Schmid L, Marquetand P, Bäck A, Borter JH, Lücken J, Dechert S, Wenger OS, Siewert I, Schwarzer D, González L, Meyer F. Luminescent Iridium Complexes with a Sulfurated Bipyridine Ligand: PCET Thermochemistry of the Disulfide Unit and Photophysical Properties. Inorg Chem 2022; 61:13944-13955. [PMID: 36001121 DOI: 10.1021/acs.inorgchem.2c01930] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Molecular systems combining light harvesting and charge storage are receiving great attention in the context of, for example, artificial photosynthesis and solar fuel generation. As part of ongoing efforts to develop new concepts for photoinduced proton-coupled electron transfer (PCET) reactivities, we report a cyclometallated iridium(III) complex [Ir(ppy)2(S-Sbpy)](PF6) ([1]PF6) equipped with our previously developed sulfurated bipyridine ligand S-Sbpy. A new one-step synthetic protocol for S-Sbpy is developed, starting from commercially available 2,2'-bipyridine, which significantly facilitates the use of this ligand. [1]+ features a two-electron reduction with potential inversion (|E1| > |E2|) at moderate potentials (E1 = -1.12, E2 = -1.11 V versus. Fc+/0 at 253 K), leading to a dithiolate species [1]-. Protonation with weak acids allows for determination of pKa = 23.5 in MeCN for the S-H···S- unit of [1H]. The driving forces for both the H atom and the hydride transfer are calculated to be ∼60 kcal mol-1 and verified experimentally by reaction with a suitable H atom and a hydride acceptor, demonstrating the ability of [1]+ to serve as a versatile PCET reagent, albeit with limited thermal stability. In MeCN solution, an orange emission for [1]PF6 from a triplet-excited state was found. Density functional calculations and ultrafast absorption spectroscopy are used to give insight into the excited-state dynamics of the complex and suggest a significantly stretched S-S bond for the lowest triplet-state T1. The structural responsiveness of the disulfide unit is proposed to open an effective relaxation channel toward the ground state, explaining the unexpectedly short lifetime of [1]+. These insights as well as the quantitative ground-state thermochemistry data provide valuable information for the use of S-Sbpy-functionalized complexes and their disulfide-/dithiol-directed PCET reactivity.
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Affiliation(s)
- Manuel Oelschlegel
- Institute of Inorganic Chemistry, University of Göttingen, Tammannstr. 4, D-37077 Göttingen, Germany
| | - Shao-An Hua
- Institute of Inorganic Chemistry, University of Göttingen, Tammannstr. 4, D-37077 Göttingen, Germany
| | - Lucius Schmid
- Department of Chemistry, University of Basel, CH-4056Basel, Switzerland
| | - Philipp Marquetand
- Institute of Theoretical Chemistry, University of Vienna, Währingerstraße 17, A-1090 Vienna, Austria
| | - Anna Bäck
- Institute of Theoretical Chemistry, University of Vienna, Währingerstraße 17, A-1090 Vienna, Austria
| | - Jan-Hendrik Borter
- Department of Dynamics at Surfaces, Max-Planck-Institute for Multidisciplinary Sciences, Am Faßberg 11, D-37077 Göttingen, Germany
| | - Jana Lücken
- Institute of Inorganic Chemistry, University of Göttingen, Tammannstr. 4, D-37077 Göttingen, Germany
| | - Sebastian Dechert
- Institute of Inorganic Chemistry, University of Göttingen, Tammannstr. 4, D-37077 Göttingen, Germany
| | - Oliver S Wenger
- Department of Chemistry, University of Basel, CH-4056Basel, Switzerland
| | - Inke Siewert
- Institute of Inorganic Chemistry, University of Göttingen, Tammannstr. 4, D-37077 Göttingen, Germany
| | - Dirk Schwarzer
- Department of Dynamics at Surfaces, Max-Planck-Institute for Multidisciplinary Sciences, Am Faßberg 11, D-37077 Göttingen, Germany
| | - Leticia González
- Institute of Theoretical Chemistry, University of Vienna, Währingerstraße 17, A-1090 Vienna, Austria
| | - Franc Meyer
- Institute of Inorganic Chemistry, University of Göttingen, Tammannstr. 4, D-37077 Göttingen, Germany.,International Center for Advanced Studies of Energy Conversion (ICASEC), D-37077 Göttingen, Germany
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