Orientation of Chiral Schiff Base Metal Complexes Involving Azo-Groups for Induced CD on Gold Nanoparticles by Polarized UV Light Irradiation

Abstract

In this study, we report the synthesis, characterization, and chiroptical properties of azo-group-containing chiral salen type Schiff base Ni(II), Cu(II), and Zn(II) complexes absorbed on gold nanoparticles (AuNPs) of 10 nm diameters. Induced circular dichroism (CD) around the plasmon region from the chiral species weakly adsorbed on the surface of AuNP were observed when there were appropriate dipole−dipole interactions at the initial states. Spectral changes were also observed by not only cis-trans photoisomerization of azo-groups but also changes of orientation due to Weigert effect of azo-dyes after linearly polarized UV light irradiation. Spatial features were discussed based on dipole-dipole interactions mainly within an exciton framework.

Keywords

• chirality
• azobenzene
• photo-isomerization
• Weigert effect
• Schiff base complexes
• gold nanoparticles
• time-dependent density functional theory (TD-DFT)