Comparative optical studies of naphthalene based Schiff base complexes for colour tunable application

Two Schiff base ligands were synthesized by the chemical reaction of 2,3-diaminonaphthalene with salicylaldehyde (HL1) and 2,3-diaminonaphthalene with 2-hydroxy-1-naphthaldehyde (HL2). The ligand HL2 have an additional phenyl group in the structure compared to HL1. This additional phenyl group in the molecular structure is expected to modify the optical and photometric properties of the ligand. The complexation of Zn metal ions with ligands occur via N-azomethine followed by the deprotonation of OH group. The complexes HC1 and HC2 were characterized by FTIR, HNMR, UV-VIS and PL techniques. The optical properties like absorption and fluorescence were studied to get the idea about the transitions among molecular orbitals as well as quantum yield. The complex having an additional phenyl group shows a blue shift in emission wavelength with an improvement in quantum yield. HOMO-LUMO energy gap along with some molecular parameters were estimated in order to know the chemical reactivity as well as to understand charge transfer process in the ligands and complexes.