Journal ArticleDOI
Trans-cis isomerization of vinylketones through triplet 1,2-biradicals.
R. A. A. Upul Ranaweera,Tianeka Scott,Qian Li,Sridhar Rajam,Alexander Duncan,Rui Li,Anthony S. Evans,Cornelia Bohne,John P. Toscano,Bruce S. Ault,Anna D. Gudmundsdottir +10 more
TLDR
DFT calculations were used to aid in the characterization of the excited states and biradicals involved in the cis-trans isomerization and to support the mechanism for the cis theomerization on the triplet surface.Abstract:
The irradiation of trans-vinylketones 1a–c yields the corresponding cis isomers 2a–c. Laser flash photolysis of 1a and 1b with 308 and 355 nm lasers results in their triplet ketones (T1K of 1), which rearrange to form triplet 1,2-biradicals 3a and 3b, respectively, whereas irradiation with a 266 nm laser produces their cis-isomers through singlet reactivity. Time-resolved IR spectroscopy of 1a with 266 nm irradiation confirmed that 2a is formed within the laser pulse. In comparison, laser flash photolysis of 1c with a 308 nm laser showed only the formation of 2c through singlet reactivity. At cryogenic temperatures, the irradiation of 1 also resulted in 2. DFT calculations were used to aid in the characterization of the excited states and biradicals involved in the cis–trans isomerization and to support the mechanism for the cis–trans isomerization on the triplet surface.read more
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Tailoring flavins for visible light photocatalysis: organocatalytic [2+2] cycloadditions mediated by a flavin derivative and visible light
Viktor Mojr,Eva Svobodová,Karolina Strakova,Tomáš Neveselý,Josef Chudoba,Hana Dvořáková,Radek Cibulka +6 more
TL;DR: 1-Butyl-7,8-dimethoxy-3-methylalloxazine, when irradiated by visible light, was shown to allow an efficient cyclobutane ring formation via an intramolecular [2+2] cycloaddition of both styrene dienes, considered as electron-rich substrates, and electron-poor bis(arylenones), presumably proceeding via an energy transfer mechanism.
Journal ArticleDOI
Flavin Photocatalysts for Visible‐Light [2+2] Cycloadditions: Structure, Reactivity and Reaction Mechanism
Viktor Mojr,Gabriela Pitrová,Karolina Strakova,Dorota Prukała,Sabina Brazevic,Eva Svobodová,Irena Hoskovcová,Gotard Burdzinski,Tomáš Slanina,Tomáš Slanina,Marek Sikorski,Radek Cibulka +11 more
TL;DR: In this paper, new photocatalysts from the flavin family were found to mediate the [2+2] photocycloaddition reaction, and they were shown to allow an efficient (Φ ~ 3-10%) intramolecular cyclization of various types of substrates including substituted styrene dienes and bis(aryl enones), considered as electron-rich and electron-poor substrates, respectively.
Journal ArticleDOI
Solvent controlling excited state proton transfer reaction in quinoline/isoquinoline-pyrazole isomer QP-I: A theoretical study
TL;DR: In this paper, the authors theoretically study the excited state intramolecular proton transfer (ESIPT) mechanism about a quinoline/isoquinoline-pyrazole isomer QP-I system.
Journal ArticleDOI
Mechanism of Photochemical O‑Atom Exchange in Nitrosamines with Molecular Oxygen
Marilene Silva Oliveira,Marilene Silva Oliveira,Ashwini A. Ghogare,Inna Abramova,Edyta M. Greer,Fernanda M. Prado,Paolo Di Mascio,Alexander Greer +7 more
TL;DR: A density functional theory study of the structures and energetics of peroxy intermediates arising from reaction of nitrosamines with O2 is presented and found not to be introduced by moisture or by singlet oxygen.
Journal ArticleDOI
Singlet Photoreactivity of 3-Methyl-2-phenyl-2H-azirine
Geethika K. Weragoda,Anushree Das,Sujan K. Sarkar,H. Dushanee M. Sriyarathne,Xiaoming Zhang,Bruce S. Ault,Anna D. Gudmundsdottir +6 more
TL;DR: In this article, a density functional theory calculation was performed to support the characterisation of ylide 6 in solution and argon matrices, which has a transient absorption with λmax at ~340nm and a lifetime of 14 μs.
References
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