1
|
Yagi S, Kawano M, Abe J. Drastically Accelerated Radical Recombination Kinetics of a Hexaarylbiimidazole Derivative. J Phys Chem Lett 2024; 15:6190-6193. [PMID: 38836752 DOI: 10.1021/acs.jpclett.4c01477] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2024]
Abstract
More than 60 years have passed since the discovery of hexaarylbiimidazole (HABI), which exhibits a characteristic photochromism that produces colored lophyl radicals through a radical dissociation reaction induced by light irradiation and reverts to its original state through a radical recombination reaction in the dark. Lophyl radicals are relatively stable among organic radicals, have low reactivity with oxygen, and have a very slow radical recombination reaction rate. HABI has been used industrially as a photoinitiator to date. However, the guidelines for molecular design to accelerate the thermal reverse reaction of HABI are still unknown and remain a challenge. We found that suppressing the rotation of the phenyl groups attached to the 4- and 5-positions of the imidazole ring of HABI is effective in accelerating the radical recombination reaction. The simple molecular design strategy to accelerate the thermal reverse reaction of HABI is expected to improve the performance of photoinitiators and photoresponsive materials that utilize HABI as a photoresponsive unit.
Collapse
Affiliation(s)
- Shiori Yagi
- Department of Chemistry and Biological Science, College of Science and Engineering, Aoyama Gakuin University, Sagamihara, Kanagawa 252-5258, Japan
| | - Masaki Kawano
- Department of Chemistry, School of Science, Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8551, Japan
| | - Jiro Abe
- Department of Chemistry and Biological Science, College of Science and Engineering, Aoyama Gakuin University, Sagamihara, Kanagawa 252-5258, Japan
| |
Collapse
|
2
|
Okamoto K, Hatano S, Abe M. Thermal Reaction Behavior of Triphenylimidazolyl Radical with a Bulky Substituent. J Org Chem 2022; 87:6877-6885. [PMID: 35503527 DOI: 10.1021/acs.joc.2c00672] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The triphenylimidazolyl radical (TPIR) is generated by the irradiation of the photochromic molecule hexaarylbiimidazole (1,2'-HABI). Usually, the unsubstituted TPIRs form 1,2'-HABI thermally at room temperature. In this study, we report the thermal reaction behavior of TPIR with a tBu group (tBu-TPIR) under N2 atmosphere and the novel reactivities of TPIRs. Under N2 atmosphere at room temperature, tBu-TPIRs form SpI with a spiro carbon and a novel HABI isomer tBu-1,4'-HABI, whose bonding pattern is different from that of the original unsubstituted HABI (1,2'-HABI). The results of 1H NMR spectroscopy, EPR measurements, and DFT calculations revealed that SpI is generated via three steps: (1) intramolecular hydrogen transfer from the tBu group to the nitrogen atom of the imidazole ring, (2) intramolecular cyclization of alkyl radicals, and (3) intermolecular hydrogen transfer with another tBu-TPIR. Furthermore, we found that the thermal reaction of tBu-TPIR at a low temperature affords the diastereomers of other isomers (tBu-4,4'-HABI_RS and tBu-4,4'-HABI_RR); in other words, the thermal reaction of tBu-TPIR depends on temperature.
Collapse
Affiliation(s)
- Kazunori Okamoto
- Basic Chemistry Program, Graduate School of Advanced Science and Engineering, Hiroshima University, Higashi-Hiroshima 739-8526, Japan
| | - Sayaka Hatano
- Basic Chemistry Program, Graduate School of Advanced Science and Engineering, Hiroshima University, Higashi-Hiroshima 739-8526, Japan
| | - Manabu Abe
- Basic Chemistry Program, Graduate School of Advanced Science and Engineering, Hiroshima University, Higashi-Hiroshima 739-8526, Japan
| |
Collapse
|
3
|
Truong VX, Barner-Kowollik C. Photodynamic covalent bonds regulated by visible light for soft matter materials. TRENDS IN CHEMISTRY 2022. [DOI: 10.1016/j.trechm.2022.01.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
|
4
|
Gotico P, Herrero C, Protti S, Quaranta A, Sheth S, Fallahpour R, Farran R, Halime Z, Sircoglou M, Aukauloo A, Leibl W. Proton-controlled Action of an Imidazole as Electron Relay in a Photoredox Triad. Photochem Photobiol Sci 2022; 21:247-259. [PMID: 34988933 DOI: 10.1007/s43630-021-00163-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Accepted: 12/18/2021] [Indexed: 11/24/2022]
Abstract
Electron relays play a crucial role for efficient light-induced activation by a photo-redox moiety of catalysts for multi-electronic transformations. Their insertion between the two units reduces detrimental energy transfer quenching while establishing at the same time unidirectional electron flow. This rectifying function allows charge accumulation necessary for catalysis. Mapping these events in photophysical studies is an important step towards the development of efficient molecular photocatalysts. Three modular complexes comprised of a Ru-chromophore, an imidazole electron relay function, and a terpyridine unit as coordination site for a metal ion were synthesized and the light-induced electron transfer events studied by laser flash photolysis. In all cases, formation of an imidazole radical by internal electron transfer to the oxidized chromophore was observed. The effect of added base evidenced that the reaction sequence depends strongly on the possibility for deprotonation of the imidazole function in a proton-coupled electron transfer process. In the complex with MnII present as a proxy for a catalytic site, a strongly accelerated decay of the imidazole radical together with a decreased rate of back electron transfer from the external electron acceptor to the oxidized complex was observed. This transient formation of an imidazolyl radical is clear evidence for the function of the imidazole group as an electron relay. The implication of the imidazole proton and the external base for the kinetics and energetics of the electron trafficking is discussed.
Collapse
Affiliation(s)
- Philipp Gotico
- Institut de Biologie Intégrative de La Cellule (I2BC), Université Paris Saclay, CEA, CNRS, 91191, Gif-sur-Yvette, France
| | - Christian Herrero
- Institut de Chimie Moléculaire Et Des Matériaux d'Orsay (ICMMO), Université Paris Saclay, 91405, Orsay, France
| | - Stefano Protti
- PhotoGreen Lab, Department of Chemistry, University of Pavia, 27100, Pavia, Italy
| | - Annamaria Quaranta
- Institut de Biologie Intégrative de La Cellule (I2BC), Université Paris Saclay, CEA, CNRS, 91191, Gif-sur-Yvette, France
| | - Sujitraj Sheth
- Institut de Biologie Intégrative de La Cellule (I2BC), Université Paris Saclay, CEA, CNRS, 91191, Gif-sur-Yvette, France
| | - Reza Fallahpour
- Department of Chemistry, University of Zürich UZH, Freiestrasse 3, CH-3012, Bern, Switzerland
| | - Rajaa Farran
- Institut de Biologie Intégrative de La Cellule (I2BC), Université Paris Saclay, CEA, CNRS, 91191, Gif-sur-Yvette, France.,Lebanese International University, Mazraa, Beirut, 146404, Lebanon
| | - Zakaria Halime
- Institut de Chimie Moléculaire Et Des Matériaux d'Orsay (ICMMO), Université Paris Saclay, 91405, Orsay, France
| | - Marie Sircoglou
- Institut de Chimie Moléculaire Et Des Matériaux d'Orsay (ICMMO), Université Paris Saclay, 91405, Orsay, France
| | - Ally Aukauloo
- Institut de Chimie Moléculaire Et Des Matériaux d'Orsay (ICMMO), Université Paris Saclay, 91405, Orsay, France
| | - Winfried Leibl
- Institut de Biologie Intégrative de La Cellule (I2BC), Université Paris Saclay, CEA, CNRS, 91191, Gif-sur-Yvette, France.
| |
Collapse
|
5
|
|
6
|
Honda S, Ikuta N, Oka M, Yamaguchi S, Handa S. Cyclic Perfluoropolyether: Distinct Film Formability and Thermostabilization Upon Recyclable Cyclic-Linear Topological Transformation. Macromol Rapid Commun 2021; 43:e2100567. [PMID: 34669216 DOI: 10.1002/marc.202100567] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2021] [Revised: 10/18/2021] [Indexed: 11/11/2022]
Abstract
Perfluoropolyether (PFPE) is an industrially important fluoropolymer and has great industrial importance due to its flexible, noncombustible, and chemically robust properties. However, exploration and application of chemically modified homogeneous PFPEs are hampered by their immiscibility against nonfluorine-containing molecules. Here, the synthesis is reported of cyclic PFPE with hexaarylbiimidazoles (HABIs) in chains from linear PFPE having 2,4,5-triphenylimidazole (lophine) end groups. While phase separation between the end groups and main chains took place for linear PFPE, HABIs and main chains in cyclic PFPE are miscible to form transparent glass films. The design of cyclic PFPE also enables cyclic to linear topological transformation based on conversion of HABIs into lophines upon mild heating in the glass film state. Sequential linear-to-cyclic and cyclic-to-linear topological transformations enable fabrication of thermostabilized transparent films derived from PFPE.
Collapse
Affiliation(s)
- Satoshi Honda
- Department of Basic Science, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo, 153-8902, Japan
| | - Naoya Ikuta
- Department of Basic Science, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo, 153-8902, Japan
| | - Minami Oka
- Department of Basic Science, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo, 153-8902, Japan
| | - Shuhei Yamaguchi
- Technology and Innovation Center, Daikin Industries, Ltd., 1-1, Nishi-Hitotsuya, Settsu, Osaka, 566-8585, Japan
| | - Shinya Handa
- Technology and Innovation Center, Daikin Industries, Ltd., 1-1, Nishi-Hitotsuya, Settsu, Osaka, 566-8585, Japan
| |
Collapse
|
7
|
|
8
|
Li YH, Chen YC. Triphenylamine-hexaarylbiimidazole derivatives as hydrogen-acceptor photoinitiators for free radical photopolymerization under UV and LED light. Polym Chem 2020. [DOI: 10.1039/c9py01605h] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
In this study, three triphenylamine-based hexaarylbiimidazole (HABI) derivatives featuring different numbers of methoxy groups (none for HABI1, two for HABI2, and four for HABI3) have been synthesized.
Collapse
Affiliation(s)
- Yan-Heng Li
- Department of Chemical and Materials Engineering
- National Kaohsiung University of Science and Technology
- Kaohsiung 80778
- Republic of China
| | - Yung-Chung Chen
- Department of Chemical and Materials Engineering
- National Kaohsiung University of Science and Technology
- Kaohsiung 80778
- Republic of China
- Photo-sensitive Material Advanced Research and Technology Center (Photo-SMART)
| |
Collapse
|
9
|
Calvino C, Weder C. Microcapsule-Containing Self-Reporting Polymers. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2018; 14:e1802489. [PMID: 30265445 DOI: 10.1002/smll.201802489] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Revised: 08/28/2018] [Indexed: 06/08/2023]
Abstract
Self-reporting polymers, which can indicate damage or exposure to excessive stress with a clearly perceptible optical signal, are potentially useful for several technological applications, including stress-sensitive sensors that enable in situ monitoring of mechanical events and structural health monitoring systems. A versatile and simple concept to realize this function is the exploitation of microcapsules that are filled with solutions of dyes that are released and chemically or physically activated when the protective shell is damaged. Such microcapsules can readily be incorporated into polymers and the composites thus made can be processed into films, coatings, or other objects. Mechanochromic effects can be realized with different types of dyes and activation schemes. In this concept article, a selection of recent key studies is presented to provide an overview of the state of the field. Different architectures and operating principles and their advantages and drawbacks are reviewed. The parameters that influence the design of microcapsule-based mechanochromic systems are considered and unexplored chromophore systems that might be useful to design future self-reporting polymers are discussed. Finally, specific aspects of capsule design, fabrication, and integration into polymers are presented. Throughout the article, challenges and opportunities of the concept are highlighted and possible future directions are discussed.
Collapse
Affiliation(s)
- Céline Calvino
- Adolphe Merkle Institute, University of Fribourg, Chemin des Verdiers 4, CH-1700, Fribourg, Switzerland
| | - Christoph Weder
- Adolphe Merkle Institute, University of Fribourg, Chemin des Verdiers 4, CH-1700, Fribourg, Switzerland
| |
Collapse
|
10
|
Herder M, Lehn JM. The Photodynamic Covalent Bond: Sensitized Alkoxyamines as a Tool To Shift Reaction Networks Out-of-Equilibrium Using Light Energy. J Am Chem Soc 2018; 140:7647-7657. [DOI: 10.1021/jacs.8b03633] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Martin Herder
- Institut de Science et d’Ingénierie Supramoléculaires, Université de Strasbourg, 8 allée Gaspard Monge, 67000 Strasbourg, France
| | - Jean-Marie Lehn
- Institut de Science et d’Ingénierie Supramoléculaires, Université de Strasbourg, 8 allée Gaspard Monge, 67000 Strasbourg, France
| |
Collapse
|
11
|
Stepwise two-photon absorption processes utilizing photochromic reactions. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY C-PHOTOCHEMISTRY REVIEWS 2018. [DOI: 10.1016/j.jphotochemrev.2017.12.006] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
|
12
|
Verstraeten F, Göstl R, Sijbesma RP. Stress-induced colouration and crosslinking of polymeric materials by mechanochemical formation of triphenylimidazolyl radicals. Chem Commun (Camb) 2018; 52:8608-11. [PMID: 27326922 DOI: 10.1039/c6cc04312g] [Citation(s) in RCA: 92] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Under mechanical stress, the hexaarylbiimidazole (HABI) motif can cleave to triphenylimidazolyl radicals when incorporated into a polymer matrix. The mechanically produced coloured radicals can initiate secondary radical reactions yielding polymer networks. Thus, the HABI mechanophore combines optical reporting of bond scission and reinforcement of polymers in a single molecular moiety.
Collapse
Affiliation(s)
- F Verstraeten
- Technische Universiteit Eindhoven, Molecular Science and Technology, Group Supramolecular Polymer Chemistry, P.O. Box 513, 5600 MB Eindhoven, The Netherlands.
| | - R Göstl
- Technische Universiteit Eindhoven, Molecular Science and Technology, Group Supramolecular Polymer Chemistry, P.O. Box 513, 5600 MB Eindhoven, The Netherlands.
| | - R P Sijbesma
- Technische Universiteit Eindhoven, Molecular Science and Technology, Group Supramolecular Polymer Chemistry, P.O. Box 513, 5600 MB Eindhoven, The Netherlands.
| |
Collapse
|
13
|
Hexaarylbiimidazoles as visible light thiol-ene photoinitiators. Dent Mater 2015; 31:1075-1089. [PMID: 26119702 DOI: 10.1016/j.dental.2015.06.005] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2014] [Revised: 04/09/2015] [Accepted: 06/02/2015] [Indexed: 11/22/2022]
Abstract
OBJECTIVES The aim of this study is to determine if hexaarylbiimidazoles (HABIs) are efficient, visible light-active photoinitiators for thiol-ene systems. We hypothesize that, owing to the reactivity of lophyl radicals with thiols and the necessarily high concentration of thiol in thiol-ene formulations, HABIs will effectively initiate thiol-ene polymerization upon visible light irradiation. METHODS UV-vis absorption spectra of photoinitiator solutions were obtained using UV-vis spectroscopy, while EPR spectroscopy was used to confirm radical species generation upon HABI photolysis. Functional group conversions during photopolymerization were monitored using FTIR spectroscopy, and thermomechanical properties were determined using dynamic mechanical analysis. RESULTS The HABI derivatives investigated exhibit less absorptivity than camphorquinone at 469nm; however, they afford increased sensitivity at this wavelength when compared with bis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide. Photolysis of the investigated HABIs affords lophyl radicals. Affixing hydroxyhexyl functional groups to the HABI core significantly improved solubility. Thiol-ene resins formulated with HABI photoinitiators polymerized rapidly upon irradiation with 469nm. The glass transition temperatures of the thiol-ene resin formulated with a bis(hydroxyhexyl)-functionalized HABI and photopolymerized at room and body temperature were 49.5±0.5°C and 52.2±0.1°C, respectively. SIGNIFICANCE Although thiol-enes show promise as continuous phases for composite dental restorative materials, they show poor reactivity with the conventional camphorquinone/tertiary amine photoinitiation system. Conversely, despite their relatively low visible light absorptivity, HABI photoinitiators afford rapid thiol-ene photopolymerization rates. Moreover, minor structural modifications suggest pathways for improved HABI solubility and visible light absorption.
Collapse
|