Synthesis, spectral characterization, magnetic, thermal and molecular docking studies of new thiosemicarbazone-based Schiff base ligands derived from Benzil and Benzoin, and Their Co (II) and Ni (II) Complexes

Abstract

Two new thiosemicarbazone-type Schiff base ligands, [L1] and [L2], were synthesized in high purity by refluxing (7 h, 70–75 °C, glacial acetic acid catalyst) an ethanolic solution of N-phenylhydrazinecarbothioamide with benzil and benzoin, respectively, and were subsequently reacted with hydrated CoCl2 and NiCl2 (2:1 ligand:metal molar ratio, 4 h reflux at 70–75 °C) to give the corresponding octahedral Co(II) and Ni(II) chelates. The ligands and their metal complexes were characterized by melting point, yield, elemental composition, FT-IR, UV-Visible, 1H- and 13C-NMR, mass spectrometry, magnetic susceptibility, thermogravimetric analysis (TGA), and frontier molecular orbital (HOMO/LUMO) calculations. The spectral evidence supports coordination of the metal ions through the azomethine nitrogen and thioamide sulfur/nitrogen donor sites, giving predominantly octahedral geometries for the hydrated Co(II) and Ni(II) chelates, in agreement with their measured magnetic moments. Molecular docking of L1 and L2 against the human enzyme Phosphodiesterase 3A (PDE3A) was performed to evaluate their potential as enzyme-binding scaffolds, and the resulting binding energies, hydrogen-bonding interactions and docking scores are reported and discussed in the context of the reported pharmacological relevance of PDE3A.