Photochromic behaviour of Copper(I) and Silver (I) complexes of 1-alkyl-2-(arylazo)imidazoles in miceller media

Abstract

Photochromism, a fast reversible structural change even at less than a femto second order upon irradiation of light, is largely influenced by the environment such as, polarity of media, existence of non-covalent interactions, hydrogen bonding etc. In this work, the micelle environment has been imposed on [Cu(RaaiR')₂]ClO₄ and [Ag(RaaiR')₂]NO₃ (RaaiR^' = 1-alkyl-2-(arylazo)imidazole) in MeOH solution using Triton-X-100 (CMC, 108 ± 1.16 at 298 K), CTAB (CMC, 51.64 ± 1.04 at 298 K) and SDS (CMC, 207.01 ± 1.51 at 298 K). 1-alkyl-2-(arylazo)imidazole undergoes <em>trans-</em>to<em>-cis</em> and <em>vice-versa</em> isomerization about –N=N- bond upon light irradiation. The quantum yield (ϕ_t_→_c) of the photoisomerization follows the order - nonionic micelle (Triton-X-100) > Cationic micelle (CTAB) > no micelle > anionic micelle (SDS). The <em>cis</em>-to-<em>trans</em> isomerization is a thermally induced process. The activation energy of <em>cis</em>-to-<em>trans</em> isomerization is calculated by controlled temperature (298–313 K) experiment. Triton-X-100 and CTAB amplify the activation energy of <em>cis</em> → <em>trans</em> thermal isomerization while SDS reduces it.