Fast and Efficient Oxidative Cycloreversion Reaction of a π‐Extended Photochromic Terarylene. Issue 29 (6th July 2016)

• Record Type: Journal Article
• Authors: Calupitan, Jan Patrick; Nakashima, Takuya; Hashimoto, Yuichiro; Kawai, Tsuyoshi
• Is Part Of: Chemistry. Volume 22:Issue 29(2016)
• Page Start: 10002
• Page End: 10008
• Publication Date: 2016-07-06
• Subjects: chain reaction -- density functional calculations -- kinetics -- photochromism -- terarylene; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201600708
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: We report herein a dramatic improvement in the kinetics and efficiency of an oxidative cycloreversion reaction of photochromic dithiazolylthiazoles. The cycloreversion reaction of a colored isomer of dithiazolylthiazole proceeds not only by photo‐irradiation, but also through chemical oxidation with a net efficiency far exceeding 100 % owing to a chain reaction mechanism. By introducing aromatic groups on the reactive carbon atoms at the ends of a photoreactive 6π system in a dithiazolylthiazole, the net bleaching reaction rates were increased by up to 1300‐fold, and turnover rates increased by two orders of magnitude. Based on a combination of classical kinetic analyses and DFT calculations, we attribute this improvement to acceleration of the rate‐determining step to produce the active species in the chain‐reaction oxidative cycloreversion. Abstract : Accelerated oxidative cycloreversion : The kinetics and efficiency of an oxidative decoloration reaction in a photochromic terthiazole have been found to be extremely improved by substituents at both ends of a reactive 6π system. Aryl substituents at the ends of the 6π system dramatically accelerate the non‐photochemical cycloreversion reaction in the radical cation state, which is the rate‐limiting step in the oxidative cycloreversion with a chain reaction mechanism (see graphic).