Metal Complexes of a Thiosemicarbazone with Heterocyclic Bases as Coligands: Spectral Characterization, Crystal Structures, DFT and In silico Docking Studies

Copper(II) and zinc(II) complexes, [Cu(esct)(4-pico)] (1), [Zn(esct)(5,5′-dmbipy)]·H₂O (2), [Cu(esct)(5,5′-dmbipy)] (3), (where H₂esct = 3-ethoxysalicylaldehye-N⁴-cyclohexylthiosemicarbazone) were synthesized by reacting copper acetate/zinc acetate with the thiosemicarbazone derivative (H₂esct) along with heterocyclic bases. The thiosemicarbazone forms doubly deprotonated anions in all the complexes to coordinate via thiolate S, azomethine N and phenolate O atoms. The complexes were characterized by various spectroscopic techniques like infrared, UV–vis, ¹H NMR and EPR spectra. The single crystal XRD studies confirmed the structures. All the three complexes got crystallized in triclinic space group P \(\overline{1 }.\) Complexes are found to have four, five and six coordination around the metal center. The importance of van der Waals interactions in them is explained by Hirshfeld surface analysis. We have used Density Functional Theory (DFT) methods and optimized ground states of the studied complexes using the Gaussian 09 package. Electrostatic potential plots of complexes were investigated. Further, docking studies were carried out with various Epidermal Growth Factor Receptor (EGFR) enzymes.

Graphical Abstract

Three mixed ligand Cu(II) and Zn(II) complexes prepared from a thiosemicarbazone showed interesting geometries and structures