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

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 trans-to-cis and vice-versa isomerization about -N=N- bond upon light irradiation. The quantum yield (phi(t -> c)) of the photoisomerization follows the order - nonionic micelle (Triton-X-100) > Cationic micelle (CTAB) > no micelle > anionic micelle (SDS). The cis-to-trans isomerization is a thermally induced process. The activation energy of cis-to-trans isomerization is calculated by controlled temperature (298-313 K) experiment. Triton-X-100 and CTAB amplify the activation energy of cis -> trans thermal isomerization while SDS reduces it.