Cargando…
Photochemical α-Cleavage Reaction of 3’,5’-Dimethoxybenzoin: A Combined Time-Resolved Spectroscopy and Computational Chemistry Study
Benzoin is one of the most commonly used photoinitiators to induce free radical polymerization. Here, improved benzoin properties could be accomplished by the introduction of two methoxy substituents, leading to the formation of 3’,5’-dimethoxybenzoin (DMB) which has a higher photo-cleavage quantum...
Autores principales: | , , , , , |
---|---|
Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
MDPI
2020
|
Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7435414/ https://www.ncbi.nlm.nih.gov/pubmed/32756525 http://dx.doi.org/10.3390/molecules25153548 |
_version_ | 1783572334328676352 |
---|---|
author | Li, Yuanchun Zhang, Xiting Yan, Zhiping Du, Lili Tang, Wenjian Phillips, David Lee |
author_facet | Li, Yuanchun Zhang, Xiting Yan, Zhiping Du, Lili Tang, Wenjian Phillips, David Lee |
author_sort | Li, Yuanchun |
collection | PubMed |
description | Benzoin is one of the most commonly used photoinitiators to induce free radical polymerization. Here, improved benzoin properties could be accomplished by the introduction of two methoxy substituents, leading to the formation of 3’,5’-dimethoxybenzoin (DMB) which has a higher photo-cleavage quantum yield (0.54) than benzoin (0.35). To elucidate the underlying reaction mechanisms of DMB and obtain direct information of the transient species involved, femtosecond transient absorption (fs-TA) and nanosecond transient absorption (ns-TA) spectroscopic experiments in conjunction with density functional theory/time-dependent density functional theory (DFT/TD-DFT) calculations were performed. It was found that the photo-induced α-cleavage (Norrish Type I reaction) of DMB occurred from the nπ* triplet state after a rapid intersystem crossing (ISC) process (7.6 ps), leading to the generation of phenyl radicals on the picosecond time scale. Compared with Benzoin, DMB possesses two methoxy groups which are able to stabilize the alcohol radical and thus result in a stronger driving force for cleavage and a higher quantum yield of photodissociation. Two stable conformations (cis-DMB and trans-DMB) at ground state were found via DFT calculations. The influence of the intramolecular hydrogen bond on the α-cleavage of DMB was elaborated. |
format | Online Article Text |
id | pubmed-7435414 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2020 |
publisher | MDPI |
record_format | MEDLINE/PubMed |
spelling | pubmed-74354142020-08-28 Photochemical α-Cleavage Reaction of 3’,5’-Dimethoxybenzoin: A Combined Time-Resolved Spectroscopy and Computational Chemistry Study Li, Yuanchun Zhang, Xiting Yan, Zhiping Du, Lili Tang, Wenjian Phillips, David Lee Molecules Article Benzoin is one of the most commonly used photoinitiators to induce free radical polymerization. Here, improved benzoin properties could be accomplished by the introduction of two methoxy substituents, leading to the formation of 3’,5’-dimethoxybenzoin (DMB) which has a higher photo-cleavage quantum yield (0.54) than benzoin (0.35). To elucidate the underlying reaction mechanisms of DMB and obtain direct information of the transient species involved, femtosecond transient absorption (fs-TA) and nanosecond transient absorption (ns-TA) spectroscopic experiments in conjunction with density functional theory/time-dependent density functional theory (DFT/TD-DFT) calculations were performed. It was found that the photo-induced α-cleavage (Norrish Type I reaction) of DMB occurred from the nπ* triplet state after a rapid intersystem crossing (ISC) process (7.6 ps), leading to the generation of phenyl radicals on the picosecond time scale. Compared with Benzoin, DMB possesses two methoxy groups which are able to stabilize the alcohol radical and thus result in a stronger driving force for cleavage and a higher quantum yield of photodissociation. Two stable conformations (cis-DMB and trans-DMB) at ground state were found via DFT calculations. The influence of the intramolecular hydrogen bond on the α-cleavage of DMB was elaborated. MDPI 2020-08-03 /pmc/articles/PMC7435414/ /pubmed/32756525 http://dx.doi.org/10.3390/molecules25153548 Text en © 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). |
spellingShingle | Article Li, Yuanchun Zhang, Xiting Yan, Zhiping Du, Lili Tang, Wenjian Phillips, David Lee Photochemical α-Cleavage Reaction of 3’,5’-Dimethoxybenzoin: A Combined Time-Resolved Spectroscopy and Computational Chemistry Study |
title | Photochemical α-Cleavage Reaction of 3’,5’-Dimethoxybenzoin: A Combined Time-Resolved Spectroscopy and Computational Chemistry Study |
title_full | Photochemical α-Cleavage Reaction of 3’,5’-Dimethoxybenzoin: A Combined Time-Resolved Spectroscopy and Computational Chemistry Study |
title_fullStr | Photochemical α-Cleavage Reaction of 3’,5’-Dimethoxybenzoin: A Combined Time-Resolved Spectroscopy and Computational Chemistry Study |
title_full_unstemmed | Photochemical α-Cleavage Reaction of 3’,5’-Dimethoxybenzoin: A Combined Time-Resolved Spectroscopy and Computational Chemistry Study |
title_short | Photochemical α-Cleavage Reaction of 3’,5’-Dimethoxybenzoin: A Combined Time-Resolved Spectroscopy and Computational Chemistry Study |
title_sort | photochemical α-cleavage reaction of 3’,5’-dimethoxybenzoin: a combined time-resolved spectroscopy and computational chemistry study |
topic | Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7435414/ https://www.ncbi.nlm.nih.gov/pubmed/32756525 http://dx.doi.org/10.3390/molecules25153548 |
work_keys_str_mv | AT liyuanchun photochemicalacleavagereactionof35dimethoxybenzoinacombinedtimeresolvedspectroscopyandcomputationalchemistrystudy AT zhangxiting photochemicalacleavagereactionof35dimethoxybenzoinacombinedtimeresolvedspectroscopyandcomputationalchemistrystudy AT yanzhiping photochemicalacleavagereactionof35dimethoxybenzoinacombinedtimeresolvedspectroscopyandcomputationalchemistrystudy AT dulili photochemicalacleavagereactionof35dimethoxybenzoinacombinedtimeresolvedspectroscopyandcomputationalchemistrystudy AT tangwenjian photochemicalacleavagereactionof35dimethoxybenzoinacombinedtimeresolvedspectroscopyandcomputationalchemistrystudy AT phillipsdavidlee photochemicalacleavagereactionof35dimethoxybenzoinacombinedtimeresolvedspectroscopyandcomputationalchemistrystudy |