Zn-Schiff's Base Complex as an "On-Off-On" Molecular Switch and a Fluorescence Probe for Cu and Ag Ions.

The present study presents a thorough theoretical analysis of the electronic structure and conformational preference of Schiff's base ligand N,N-bis(2-hydroxybenzilidene)-2,4,6-trimethyl benzene-1,3-diamine (HL) and its metal complexes with Zn, Cu and Ag ions. This study aims to investigate the behavior of HL and the binuclear Zn complex (1) as fluorescent probes for the detection of metal ions (Zn, Cu and Ag) using density functional theory (DFT) and time-dependent density functional theory (TDDFT). The six conformers of the HL ligand were optimized using the B3LYP/6-311 +  + G** level of theory, while the L-metal complexes were optimized by applying the B3LYP functional with the LANL2DZ/6-311 +  + G** mixed basis set.