The spectroscopic characterization, photochromism of cadmium(II)-iodo complexes of 1-alkyl-2-(arylazo)imidazoles and DFT computation of representative complexes

Abstract

[Cd(Raai-CnH2n+1)(μ-I)I]2 and [Cd(Raai-CnH2n+1)2I2] are synthesized by the reaction of CdI2 with 1-alkyl-2-(arylazo)imidazole (Raai-CnH2n+1, n=4, 6, 8) in MeOH in 1:1 and 1:2M ratio of salt and ligands, respectively. The complexes have been characterized by spectral data (UV–Vis, IR, 1H NMR, Mass). The coordinated Raai-CnH2n+1 shows photochromism, E(trans)-to-Z(cis) isomerisation, upon UV light irradiation. The reverse process, Z-to-E, is very slow in visible light irradiation process while the reaction is sensitive to change of reaction temperature. The quantum yields (ϕE→Z) for E-to-Z and the activation energy (Ea) of Z-to-E isomerisation are calculated and found that the complexes show subordinate results compared to free ligand. DFT computations of two representative complexes were carried out to explain the spectral and photochromic phenomena.