Syntheses and structural characterization of divalent metal complexes (Co, Ni, Pd and Zn) of sterically hindered thiourea ligand and a theoretical insight of their interaction with SARS-CoV-2 enzyme

Reacting two equivalents of sterically hindered 1,3-bis(2,6-diethylphenyl)thiourea ligand (L) with CoCl(2), NiBr(2), PdX(2) (X = Cl; Br) and ZnI(2) in acetonitrile afforded the corresponding bulky thiourea ligand stabilized four coordinated monomeric [L(2)CoCl(2)] (1), [L(2)NiBr(2)] (2), [L(2)PdX(2)] (3a: X = Cl; 3b: X = Br) and [L(2)ZnI(2)] (4.2CH(3)CN) complexes. Compound 1, 2 and 4.2CH(3)CN are tetrahedral whereas Pd complexes (3a and 3b) are square planar. In solution, palladium complexes are dominated by cis-isomers. Structural characterization shows inter- and intramolecular hydrogen bonding. Hirshfeld surface and fingerprint plots indicated significant intermolecular interactions in the crystal network. Molecular docking analysis revealed relatively higher SARS-CoV-2 enzyme interacting abilities of the synthesized complexes compared to the free ligand. All compounds have been characterized by elemental analyses, NMR spectroscopy and single-crystal X-ray diffraction.