The iron(III) and nickel(II) complexes with tetradentate thiosemicarbazones. Synthesis, experimental, theoretical characterization, and antiviral effect against SARS-CoV-2.

The discovery of new inhibitors that can be used in the treatment of viral diseases, including Covid-19, is an area open to research, and there is a need for innovative compounds with increased efficiency that provide inhibition by suppressing enzyme, and receptor mechanisms. The iron(III) and nickel(II) complexes were synthesized by template condensation of 4-methoxy-salicylaldehyde with S-methylthiosemicarbazone derivatives of 1,1,1-trifluoroacetylacetone (for ) and methylacetoacetate (for ). The complex structures having NO-chelating thiosemicarbazidato ligand were identified by analytical, spectroscopic, and X-ray crystallography results. Coordination environment of iron(III) center in complex has a distorted square pyramidal geometry consisting of the NO donor set and a chlorine atom, while that of is square plane with the set. Inhibitory effect of compound against SARS-CoV-2 virus specific 3C-like protease enzyme was investigated experimentally. It was determined that the highest inhibition concentration of was 100 μM. Percent inhibition activity at this concentration was on average 30.62 ± 3.809%. Binding of both compounds to the 3C-like protease enzyme specific to the SARS-CoV-2 virus was analyzed using docking calculations. As a result of the docking calculation of , it has been observed that the compound has a binding energy of -7.4 kcal / mol to 3CL-like protease. It has been observed that the protein amino acids GLY143, THR26, and ASN142 contribute to the high binding affinity of the . The experimental and theoretical results obtained for the two complexes support each other.