A naphthalene-based and hydroxyamide-functionalized hybrid Schiff base and its dimeric and dinuclear Zn(II) complex: synthesis, structural and theoretical characterization, optical, DPPH scavenging and in silico ADME properties

Abstract

A novel hybrid ligand 2b (3,5-bis((E)-((2-hydroxynaphthalen-1-yl)methylene)amino)-N-(2hydroxyphenyl)benzamide) was obtained from the amidation reaction between Schiff base 1b (3,5-bis((E)-((2-hydroxynaphthalen-1-yl)methylene)amino)benzoic acid) and 2hydroxyaniline by using dicyclohexylcarbodiimide. The coordination of 2b with zinc ions resulted in the formation of neutral dinuclear and non-electrolyte complex of 3b [Zn 2 L 2 (H 2 O) 4 ].2H 2 O at a stoichiometric 2:2 mol ratio, where each zinc(II) cation is sixcoordinate in a distorted octahedral geometry with two coordinated water molecules. They were characterized by IR, NMR and UV-Vis spectroscopy both experimentally and theoretically.Thermal and mass analyses provided information regarding the presence of water molecules.DFT simulations were performed to obtain the lowest-energy structures of the compounds. The calculated frontier molecular orbital gaps correlated well with the optical bandgaps. 1b-2b emitted strong greenish-blue and green emissions in dilute DMSO and DMF solutions. The emission color of 3b shifted to bluish-green/green. Their emission properties were evaluated in binary aqueous mixtures with varying water content (f w = 0-90%). Upon increasing the water fraction, the intensity was enhanced by changing the spectral profiles of the media. 1b-3b possess lower DPPH scavenging activity than ascorbic acid. The absorption, distribution, metabolism, and elimination (ADME) parameters were calculated for the ligands.