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Murto P, Li B, Fu Y, Walker LE, Brown L, Bond AD, Zeng W, Chowdhury R, Cho HH, Yu CP, Grey CP, Friend RH, Bronstein H. Steric Control of Luminescence in Phenyl-Substituted Trityl Radicals. J Am Chem Soc 2024; 146:13133-13141. [PMID: 38695282 PMCID: PMC11099960 DOI: 10.1021/jacs.4c00292] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2024] [Revised: 04/17/2024] [Accepted: 04/18/2024] [Indexed: 05/16/2024]
Abstract
Triphenylmethyl (trityl) radicals have shown potential for use in organic optoelectronic applications, but the design of practical trityl structures has been limited to donor/radical charge-transfer systems due to the poor luminescence of alternant symmetry hydrocarbons. Here, we circumvent the symmetry-forbidden transition of alternant hydrocarbons via excited-state symmetry breaking in a series of phenyl-substituted tris(2,4,6-trichlorophenyl)methyl (TTM) radicals. We show that 3-fold phenyl substitution enhances the emission of the TTM radical and that steric control modulates the optical properties in these systems. Simple ortho-methylphenyl substitution boosts the photoluminescence quantum efficiency from 1% (for TTM) to 65% at a peak wavelength of 612 nm (for 2-T3TTM) in solution. In the crystalline solid state, the neat 2-T3TTM radical shows a remarkably high photoluminescence quantum efficiency of 25% for emission peaking at 706 nm. This has implications in the design of aryl-substituted radical structures where the electronic coupling of the substituents influences variables such as emission, charge transfer, and spin interaction.
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Affiliation(s)
- Petri Murto
- Yusuf
Hamied Department of Chemistry, University
of Cambridge, Cambridge CB2 1EW, U.K.
- Cavendish
Laboratory, University of Cambridge, Cambridge CB3 0HE, U.K.
| | - Biwen Li
- Cavendish
Laboratory, University of Cambridge, Cambridge CB3 0HE, U.K.
| | - Yao Fu
- Yusuf
Hamied Department of Chemistry, University
of Cambridge, Cambridge CB2 1EW, U.K.
| | - Lucy E. Walker
- Yusuf
Hamied Department of Chemistry, University
of Cambridge, Cambridge CB2 1EW, U.K.
- Cavendish
Laboratory, University of Cambridge, Cambridge CB3 0HE, U.K.
| | - Laura Brown
- Yusuf
Hamied Department of Chemistry, University
of Cambridge, Cambridge CB2 1EW, U.K.
| | - Andrew D. Bond
- Yusuf
Hamied Department of Chemistry, University
of Cambridge, Cambridge CB2 1EW, U.K.
| | - Weixuan Zeng
- Yusuf
Hamied Department of Chemistry, University
of Cambridge, Cambridge CB2 1EW, U.K.
| | | | - Hwan-Hee Cho
- Cavendish
Laboratory, University of Cambridge, Cambridge CB3 0HE, U.K.
| | - Craig P. Yu
- Yusuf
Hamied Department of Chemistry, University
of Cambridge, Cambridge CB2 1EW, U.K.
- Cavendish
Laboratory, University of Cambridge, Cambridge CB3 0HE, U.K.
| | - Clare P. Grey
- Yusuf
Hamied Department of Chemistry, University
of Cambridge, Cambridge CB2 1EW, U.K.
| | - Richard H. Friend
- Cavendish
Laboratory, University of Cambridge, Cambridge CB3 0HE, U.K.
| | - Hugo Bronstein
- Yusuf
Hamied Department of Chemistry, University
of Cambridge, Cambridge CB2 1EW, U.K.
- Cavendish
Laboratory, University of Cambridge, Cambridge CB3 0HE, U.K.
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2
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Hattori Y, Yamamoto K, Kitajima R, Uchida K. Bright Fluorescent p-Phenylene-bridged Triarylmethyl Highly Stable Diradical. Chemistry 2024; 30:e202304124. [PMID: 38380885 DOI: 10.1002/chem.202304124] [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: 12/11/2023] [Revised: 02/13/2024] [Accepted: 02/19/2024] [Indexed: 02/22/2024]
Abstract
Two units of highly stable luminescent triarylmethyl radical, (3,5-dichloro-4-pyridyl)bis(2,4,6-trichlorophenyl)methyl radical (PyBTM), were bridged by p-phenylene linker. The photoluminescence quantum yield (PLQY) of PyBTM-PhPyBTM was at most 0.4 % in various organic solvents. Adding two mesityl groups on the terminals did not improve the PLQY. In the MesPyBTM-PhPyBTM-Mes, the mesityl group did not worked as an electron donor unlike the previously reported monoradical MesPyBTM. However, adding two n-hexyl groups on the bridging p-phenylene did greatly improve it, and the PLQY of the PyBTM-(Hex2Ph)PyBTM was 7 % in dichloromethane and acetone, and 12 % in poly(methyl methacrylate) (PMMA) film. Twisting p-phenylene linker by hexyl groups hindered the π-conjugation and suppressed the non-radiative decay of the excited state.
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Affiliation(s)
- Yohei Hattori
- Materials Chemistry Course, Faculty of Advanced Science and Technology, Ryukoku University Seta, Otsu, Shiga, 520-2194, Japan
| | - Kohei Yamamoto
- Materials Chemistry Course, Faculty of Advanced Science and Technology, Ryukoku University Seta, Otsu, Shiga, 520-2194, Japan
| | - Ryota Kitajima
- Materials Chemistry Course, Faculty of Advanced Science and Technology, Ryukoku University Seta, Otsu, Shiga, 520-2194, Japan
| | - Kingo Uchida
- Materials Chemistry Course, Faculty of Advanced Science and Technology, Ryukoku University Seta, Otsu, Shiga, 520-2194, Japan
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3
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Nakamura K, Matsuda K, Xiaotian R, Furukori M, Miyata S, Hosokai T, Anraku K, Nakao K, Albrecht K. Effects of halogen atom substitution on luminescent radicals: a case study on tris(2,4,6-trichlorophenyl)methyl radical-carbazole dyads. Faraday Discuss 2024; 250:192-201. [PMID: 37966049 DOI: 10.1039/d3fd00130j] [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
A series of halogen-substitute carbazole TTM radicals was synthesized. The effect of halogen substituents on radical luminescence was systematically evaluated. It was found that the well-known heavy atom effect does not work in the emission of radicals and that halogen substitution of the donor carbazole can change the HOMO and alter the absorption and emission wavelengths. In addition, the photostability was found to be improved with respect to TTM but not significantly different from that of closed-shell fluorescent molecules.
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Affiliation(s)
- Kazuhiro Nakamura
- Department of Applied Science for Electronics and Materials, Interdisciplinery Graduate School of Engineering Sciences, Kyushu University, Fukuoka 816-8580, Japan
| | - Kenshiro Matsuda
- Department of Applied Science for Electronics and Materials, Interdisciplinery Graduate School of Engineering Sciences, Kyushu University, Fukuoka 816-8580, Japan
| | - Rui Xiaotian
- Department of Applied Science for Electronics and Materials, Interdisciplinery Graduate School of Engineering Sciences, Kyushu University, Fukuoka 816-8580, Japan
| | - Minori Furukori
- Department of Pure and Applied Chemistry, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan
- National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan.
| | - Satoshi Miyata
- National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan.
| | - Takuya Hosokai
- Department of Pure and Applied Chemistry, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan
- National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan.
| | - Kosuke Anraku
- Department of Applied Science for Electronics and Materials, Interdisciplinery Graduate School of Engineering Sciences, Kyushu University, Fukuoka 816-8580, Japan
| | - Kohei Nakao
- Institute for Materials Chemistry and Engineering, Kyushu University, 6-1 Kasuga-Koen Kasuga-Shi, Fukuoka 816-8580, Japan.
| | - Ken Albrecht
- Institute for Materials Chemistry and Engineering, Kyushu University, 6-1 Kasuga-Koen Kasuga-Shi, Fukuoka 816-8580, Japan.
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4
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Mizuno A, Matsuoka R, Mibu T, Kusamoto T. Luminescent Radicals. Chem Rev 2024; 124:1034-1121. [PMID: 38230673 DOI: 10.1021/acs.chemrev.3c00613] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2024]
Abstract
Organic radicals are attracting increasing interest as a new class of molecular emitters. They demonstrate electronic excitation and relaxation dynamics based on their doublet or higher multiplet spin states, which are different from those based on singlet-triplet manifolds of conventional closed-shell molecules. Recent studies have disclosed luminescence properties and excited state dynamics unique to radicals, such as highly efficient electron-photon conversion in OLEDs, NIR emission, magnetoluminescence, an absence of heavy atom effect, and spin-dependent and spin-selective dynamics. These are difficult or sometimes impossible to achieve with closed-shell luminophores. This review focuses on luminescent organic radicals as an emerging photofunctional molecular system, and introduces the material developments, fundamental properties including luminescence, and photofunctions. Materials covered in this review range from monoradicals, radical oligomers, and radical polymers to metal complexes with radical ligands demonstrating radical-involved emission. In addition to stable radicals, transiently formed radicals generated in situ by external stimuli are introduced. This review shows that luminescent organic radicals have great potential to expand the chemical and spin spaces of luminescent molecular materials and thus broaden their applicability to photofunctional systems.
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Affiliation(s)
- Asato Mizuno
- Department of Life and Coordination-Complex Molecular Science, Institute for Molecular Science, 5-1 Higashiyama, Myodaiji, Okazaki, Aichi 444-8787, Japan
| | - Ryota Matsuoka
- Department of Life and Coordination-Complex Molecular Science, Institute for Molecular Science, 5-1 Higashiyama, Myodaiji, Okazaki, Aichi 444-8787, Japan
- SOKENDAI (The Graduate University for Advanced Studies), Shonan Village, HayamaKanagawa 240-0193, Japan
| | - Takuto Mibu
- Department of Life and Coordination-Complex Molecular Science, Institute for Molecular Science, 5-1 Higashiyama, Myodaiji, Okazaki, Aichi 444-8787, Japan
| | - Tetsuro Kusamoto
- Department of Life and Coordination-Complex Molecular Science, Institute for Molecular Science, 5-1 Higashiyama, Myodaiji, Okazaki, Aichi 444-8787, Japan
- SOKENDAI (The Graduate University for Advanced Studies), Shonan Village, HayamaKanagawa 240-0193, Japan
- JST-PRESTO, 4-1-8, Honcho, Kawaguchi, Saitama 332-0012, Japan
- Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan
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5
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Ohisa S, Honda S. Luminescence enhancement by symmetry-breaking in the excited state in radical organic light-emitting diodes. Commun Chem 2023; 6:238. [PMID: 37919478 PMCID: PMC10622504 DOI: 10.1038/s42004-023-01039-5] [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: 09/08/2023] [Accepted: 10/23/2023] [Indexed: 11/04/2023] Open
Abstract
Organic π-conjugated radicals have recently joined the ranks of high-efficiency light-emitting materials, however, their light-emission mechanism is still a matter of debate. Here, the authors highlight a recently proposed luminescent enhancement mechanism and record-breaking efficiency of a radical organic light-emitting diode.
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Affiliation(s)
- Satoru Ohisa
- Science & Technology Research Laboratories, Japan Broadcasting Corporation (NHK), 1-10-11 Kinuta, Setagaya-ku, Tokyo, 157-8510, Japan.
| | - Satoshi Honda
- Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo, 153-8902, Japan.
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6
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Murto P, Chowdhury R, Gorgon S, Guo E, Zeng W, Li B, Sun Y, Francis H, Friend RH, Bronstein H. Mesitylated trityl radicals, a platform for doublet emission: symmetry breaking, charge-transfer states and conjugated polymers. Nat Commun 2023; 14:4147. [PMID: 37438369 DOI: 10.1038/s41467-023-39834-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2023] [Accepted: 06/29/2023] [Indexed: 07/14/2023] Open
Abstract
Neutral π-radicals have potential for use as light emitters in optoelectronic devices due to the absence of energetically low-lying non-emissive states. Here, we report a defect-free synthetic methodology via mesityl substitution at the para-positions of tris(2,4,6-trichlorophenyl)methyl radical. These materials reveal a number of novel optoelectronic properties. Firstly, mesityl substituted radicals show strongly enhanced photoluminescence arising from symmetry breaking in the excited state. Secondly, photoexcitation of thin films of 8 wt% radical in 4,4'-bis(carbazol-9-yl)-1,1'-biphenyl host matrix produces long lived (in the order of microseconds) intermolecular charge transfer states, following hole transfer to the host, that can show unexpectedly efficient red-shifted emission. Thirdly, covalent attachment of carbazole into the mesitylated radical gives very high photoluminescence yield of 93% in 4,4'-bis(carbazol-9-yl)-1,1'-biphenyl films and light-emitting diodes with maximum external quantum efficiency of 28% at a wavelength of 689 nm. Fourthly, a main-chain copolymer of the mesitylated radical and 9,9-dioctyl-9H-fluorene shows red-shifted emission beyond 800 nm.
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Affiliation(s)
- Petri Murto
- Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, CB2 1EW, UK
| | | | - Sebastian Gorgon
- Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK
| | - Erjuan Guo
- Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK
- State Key Laboratory of Materials Processing and Die and Mould Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan, China
| | - Weixuan Zeng
- Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, CB2 1EW, UK
| | - Biwen Li
- Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK
| | - Yuqi Sun
- Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK
| | - Haydn Francis
- Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, CB2 1EW, UK
| | - Richard H Friend
- Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK.
| | - Hugo Bronstein
- Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, CB2 1EW, UK.
- Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK.
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7
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Ma Z, Zhang L, Cui Z, Ai X. Improving the Luminescence and Stability of Carbon-Centered Radicals by Kinetic Isotope Effect. Molecules 2023; 28:4805. [PMID: 37375360 DOI: 10.3390/molecules28124805] [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: 05/25/2023] [Revised: 06/13/2023] [Accepted: 06/14/2023] [Indexed: 06/29/2023] Open
Abstract
The kinetic isotope effect (KIE) is beneficial to improve the performance of luminescent molecules and relevant light-emitting diodes. In this work, the influences of deuteration on the photophysical property and stability of luminescent radicals are investigated for the first time. Four deuterated radicals based on biphenylmethyl, triphenylmethyl, and deuterated carbazole were synthesized and sufficiently characterized. The deuterated radicals exhibited excellent redox stability, as well as improved thermal and photostability. The appropriate deuteration of relevant C-H bonds would effectively suppress the non-radiative process, resulting in the increase in photoluminescence quantum efficiency (PLQE). This research has demonstrated that the introduction of deuterium atoms could be an effective pathway to develop high-performance luminescent radicals.
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Affiliation(s)
- Zhichao Ma
- School of Materials Science and Engineering, Collaborative Innovation Center of Information Technology, Collaborative Innovation Center of Marine Science and Technology, Hainan University, No 58, Renmin Avenue, Haikou 570228, China
| | - Lintao Zhang
- School of Materials Science and Engineering, Collaborative Innovation Center of Information Technology, Collaborative Innovation Center of Marine Science and Technology, Hainan University, No 58, Renmin Avenue, Haikou 570228, China
| | - Zhiyuan Cui
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, No. 2699, Qianjin Avenue, Changchun 130012, China
| | - Xin Ai
- School of Materials Science and Engineering, Collaborative Innovation Center of Information Technology, Collaborative Innovation Center of Marine Science and Technology, Hainan University, No 58, Renmin Avenue, Haikou 570228, China
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