Observation of Reciprocal Induced CD between Colloidal Gold Nanoparticles and Chiral Schiff Base Zn (II) Complexes with Parallel Dipole Moments

The authors have prepared suprameolecular systems of chiral Schiff base ZnAZSB (Zn(II) complexes with azo-groups) or without ZnSB (azo-groups) and colloidal AuNP (gold nanoparticles) of 10, 40 and 80 nm diameters. They exhibited gradual shifts of surface plasmon bands as well as fluorescence bands. The authors observed and discussed induced CD bands on gold nanoparticles from chiral ZnAZSB or ZnSB. Absence of cis-trans photoisomerization of ZnAZSB with AuNP also supported direct contact near the surface of AuNP. Quenching and splitting of fluorescence bands of ZnSB (λex = 550 nm and λem = 400 nm) depending on concentration of ZnSB and size of AuNP also suggested intermolecular (electric) interaction on the surface of AuNP. Decrease of the intensity of the CD band around 380 nm resulted from reciprocal induced CD effect due to parallel arrangement of electric transition moments of ZnAZSB or ZnSB and surface of AuNP.