Design, structural investigations and antimicrobial activity of pyrazole nucleating copper and zinc complexes

The present study accounts for the construction of two novel complexes by the interaction of pyrazole nucleating ligand with Cu(II) (1) and Zn(II) (2) ions in 1:1 equivalent ratio, and their structural investigation by elemental analyses, FT-IR, NMR and thermal studies. Complex 1, additionally characterized by single crystal X-ray crystallography, reveals the coordination of the pyrazole nucleating ligand to the metal ions by the imine nitrogen, carbonyl oxygen and phenolic oxygen of the ligand and chloride ion. Furthermore, the coordination environment of the central atom adopts slightly distorted square-planar geometry with sum of interbond angles equal to 701.49 degrees. The analysis of CAN bond lengths shows that the double bond is localised within imine moiety and respective bonds shows considerable degree of delocalisation within pyrazole ring. The mixed basis set 6-311G(d) and LANL2DZ with B3LYP functional is applied for DFT calculation to determine the bonding insights into the structure of the complex. Natural Population Analysis (NPA) is also carried out to define the nature of the charge on copper atom in complex 1. In addition, Hirshfeld surface analysis is also carried out to know the various intermolecular interactions. The ligand and its complexes were evaluated against Pseudomonas aeruginosa, Escherichia coli, Shigella sonnei, Bacillus subtilis, Aspergillus niger, Aspergillus flavus, Fusarium oxysporum, Penicillium notatum microbial species, and showed significant effects on the tested microbes. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

This study presents the synthesis and structural investigation of two novel complexes formed by the interaction of pyrazole nucleating ligand with Cu(II) and Zn(II) ions. Various analytical techniques were used, including X-ray crystallography, NMR, and thermal analysis. The complexes showed significant inhibitory effects on various microbial species as evaluated in the study.