Rare open zinc cluster of a novel multidentate Schiff base containing 1,2,3-triazole derivative: Stepwise synthesis, characterization, XRD, HSA, %Vbur, τ and CV studies

Abstract

A novel multidentate Schiff base ligand, N'4,N'5-bis((E)-3,5-di-tert-butyl-2-hydroxybenzylidene)-1-(2-(2-((E)-3,5-di-tert-butyl-2-hydroxybenzylidene)hydrazinyl)-2-oxoethyl)-1H-1,2,3-triazole-4,5-dicarbohydrazide (5), was successfully synthesized via an acid-catalyzed condensation reaction. The process involved reacting 1-(2-hydrazineyl-2-oxoethyl)-1H-1,2,3-triazole-4,5-dicarbohydrazide (4) with three equivalents of the appropriate aldehyde under traditional Schiff base conditions. The synthetic route began with the preparation of 1,2,3-triazole tris-ester (3) from diethyl acetylenedicarboxylate (1) and ethyl azidoacetate (2), employing a highly efficient solvent-free reaction that yielded 96 %. Subsequent hydrazinolysis of the tris-ester afforded the tris-acid hydrazide (4) in 92 % yield.

NMR spectroscopy confirmed the structure of the hydrazide with distinct NH₂ and NH protons resonating at 4.29–4.59 ppm and 8.79–9.39 ppm, respectively. Ligand 5, containing hydroxyl and nitrogen donor groups, was employed to synthesize binuclear zinc complexes with two independent zinc centers: Zn (Jos and Suja, 2023 (1)) displayed square pyramidal geometry, while Zn (Juyal et al., 2023 (2)) exhibited distorted octahedral geometry. The zinc complex crystallized in a triclinic system (P₋₁ space group) and formed a dimer stabilized by hydrogen bonding, with a packing arrangement that featured a major void stabilized by a 10-member hydrogen-bonded ring system.

Hirshfeld surface analysis (HSA) and cyclic voltammetry (CV) were performed to understand the complex's physical and electrochemical properties. Using ChimeraX software, the percent buried volume (%Vbur) was calculated, providing insights into steric interactions between the ligand and the zinc coordination sites. This analysis was essential for optimizing ligand design, minimizing steric hindrance around the metal centre. The findings of this study could aid in advancing Schiff base ligands and zinc complexes for materials science applications, though additional research is required. The results highlight the critical role of steric hindrance, NH, OH, NCH₂, NCH, ethanol solvents, and acetic acid groups attached to the zinc metal in influencing the structural and reactive properties of metal-ligand complexes, offering valuable insights into their behaviour within chemical systems.