Oxidative electrochemical aryl C–C coupling of spiropyrans

Abstract

The isolation and definitive assignment of the species formed upon electrochemical oxidation of nitro-spiropyran (SP) is reported. The oxidative aryl C-C coupling at the indoline moiety of the SP radical cation to form covalent dimers of the ring-closed SP form is demonstrated. The coupling is blocked with a methyl substituent para to the indoline nitrogen.

Dithienylethene‐Based Gated Ambichromic Dyads

“…[4b] The second process involving the BOX radical cation is an oxidative C—C coupling toward the molecule dimerization and is easily identified by the appearance of a new reversible redox system around 0.4 V on the back scan. As expected, the CV of reference hybrid 4 clearly shows the result of the dimerization process, which is kinetically favored when any substituent is present on the indoline heterocycle in position 5 …”

The evolution of spiropyran: fundamentals and progress of an extraordinarily versatile photochrome

“…Ivashenko et al showed subsequently that blocking coupling by methyl-substitution in the para-position prevents dimerization and the oxidative cyclic voltammetry thus becomes reversible (Scheme 21). 149 The blocking of the oxidative coupling by the methyl group demonstrates that the radical character lies predominantly at this position and not the chromene unit (Scheme 22). 148 Dimerization by oxidative coupling was shown later in self-assembled monolayers of nitrospiropyran also.…”

Square‐wave Voltammetric Determination of Propyphenazone, Paracetamol, and Caffeine: Comparative Study between Batch Injection Analysis and Conventional Electrochemical Systems

“…The electrochemical oxidation of PRO occurs in the tertiary nitrogen of the aromatic ring resulting in a radical cation. The proposed mechanism is in agreement with the electrochemical oxidation of N,N‐dimethylaniline which also presents a tertiary nitrogen attached to an aromatic ring .…”