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

Abstract

Photochromism, a reversible structural change of distinctive absorption feature of each isomer upon irradiation of light, is largely influenced by external environment such as polarity of media, existence of noncovalent interactions, hydrogen bonding etc. In this work, the Photochromism of [Cu(RaaiR^/)₂]ClO₄ and [Ag(RaaiR^/)₂]NO₃ complexes (RaaiR^/ = 1-alkyl-2-(arylazo)imidazole) have been examined in the micelle media in MeOH using Triton-X-100, CTAB and SDS. 1-Alkyl-2-(arylazo)imidazole undergoes trans-to-cis isomerization about –N=N- bond upon light irradiation. The quantum yield (f_t®c) of the photoisomerization follows the sequence nonionic micelle (Triton-X-100) > Cationic micelle (CTAB) >  no micelle > anioic  micelle (SDS). Although the cis-to-trans isomerization is also carried out photochemically but thermal process is faster and is followed. The activation energy (E_a) of cis-to-trans isomerization is calculated by controlled temperature (298 – 313 K) experiment. Triton-X-100 and CTAB amplify the activation energy (E_a) of cis ® trans thermal isomerization while in presence of SDS it is decreased.