The photochromism of 1-alkyl-2-(arylazo)imidazoles trapped in water pool by AOT -heptane reverse micelle

Department of Chemistry, Jadavpur University, Kolkata-700 032, India

E-mail : c_r_sinha@yahoo.com,

Manuscript received online 13 June 2012, accepted 17 July 2012

1-Aikyl-2-(arylazo)imidazole exists in trans-geometry about -N =N- group at ambient condition. UV light irradiation in (363-371 nm) in solution phase of the compounds has changed their trans-geometry to cis-structure. The cis-to-trans isomerisation proceeds slowly in visible light irradiation while it is appreciably fast on heating. The photoisomerisation rate is controlled by microenvironlment of photochrome. In this work we have examined the influence of reverse micelle (AOT/n-heptane/water) on kinetics and mechanism of photoisomerisation of azoimidazoles. The effect of [AOT] and water pool size [W] on the quantum yields of trans-to-cis isomerisation are examined. The rate of trans-to-cis transformation is increased by 5-66% with increase in [AOT]. The quantum yield is also increased by 30-120% under identical condition. The activation energy (E_a) of cis-to-trans is calculated and in presence of reverse micelle the activation energy is reduced. It justifies the enhancement of rate.