SYNTHESIS AND STUDY OF Zn COMPLEXES WITH N'-ACYL-SALICYLHYDRAZIDES

Abstract

Zn complexes with potentially tridentate (carbonyl and hydroxyl oxygen atoms of the salicylic fragment and nitrogen atom of the amide group) were synthesized by the ligand N'-phthalimido-salicylamide (H2L) and potentially heptadentate (carbonyl and hydroxyl oxygen atoms of the salicylic fragment, two nitrogen atoms of the hydrazide moiety and two oxygen atoms of the carbonyl and carboxyl groups of the maleic fragment) with the ligand N'-maleoal-salicylhydrazide (H4L) with 78% and 86% yield, respectively. The structural features of the N'-phthalimido-salicylamide (H2L) and N'-maleoyl-salicylhydrazide (H4L) obtained were established by IR and 1H and 13C NMR spectroscopy. In the 1H NMR spectra, signals from proton-containing groups are detected in the expected region. Also the structure of the ligands confirms 13C NMR spectroscopy. The yield of ligands is 92% and 95%, respectively. It was found that both ligands, in the conducted synthesis reactions, behave as bidentate, are in the enol form. Ligand-N- (salicylamide) -phthalimide is coordinated with zinc ion through the oxygen atoms of the phenol and nitrogen amide groups. The N’-maleoyl-salicylhydrazide ligand is coordinated with the zinc ion through the oxygen atoms of the salicylic residue and the nitrogen atom of the amide group of the maleic residue. The structures of synthesized Zn coordination compounds with H2L and H4L have been studied by IR and electronic absorption spectrometry, elemental analysis and thermogravimetry. These analyzes helped to establish that the metal ion in complex compounds is bound to two water molecules by a hydrogen bond and forms a distorted octahedral geometry. Coordination with water molecules is also confirmed by the TG curves, in which the first and second stages of weight loss are attributed to the removal of solvent molecules — coordinated water molecules and DMF.