Proton Catalysis in the Redox Responsivity of a Mini‐Sized Photochromic Diarylethene. Issue 37 (23rd July 2013)

• Record Type: Journal Article
• Authors: Massaad, Julie; Micheau, Jean‐Claude; Coudret, Christophe; Serpentini, Charles Louis; Guirado, Gonzalo
• Is Part Of: Chemistry. Volume 19:Issue 37(2013)
• Page Start: 12435
• Page End: 12445
• Publication Date: 2013-07-23
• Subjects: Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201301566
• Languages: English
• ISSNs: 0947-6539

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>A thermally irreversible dithienylethene (DTE) photochrom can be turned into a thermally reversible one in presence of Cu^II triflate. A ring opening (DTEC closed→DTEO open) occurs through the formation of a copper‐containing fast transient intermediate. Stopped‐flow experiments monitored at 410 and 780 nm have allowed to show that the stoichiometry of this intermediate is DTE/Cu=1:1. At longer monitoring times (i.e., several seconds after mixing), the intermediate undergoes a slow decay while the residual DTEC closed form opens. A joint detailed kinetic and electrochemical analysis has unveiled a proton catalysis scenario in which electron transfer between DTEC and Cu^II, ligand exchange, protonation‐deprotonation equilibria of the cation radicals and ring opening are embedded into two main reaction cycles. At the beginning of the reaction, Cu^II is reduced into Cu^I and DTE is degraded without ring opening. Then, as the reaction progresses, the triflic acid released from the Cu^II reduction switches‐on a propagation cycle during which ring opens without any more Cu^II consumption. Cyclic voltammetry, spectro‐electrochemical measurements, delayed photocoloration experiments in presence of Cu^II and acid–base additions have confirmed the main features of the proton catalysis.</p> </abstract>