Synthesis, spectroscopic characterization, DFT analysis and molecular docking of Mn(II), Co(II) and Ni(II) complexes of hydrazone derived from 5-chloroisatin and 2,4-dinitrophenylhydrazine

Abstract

Octahedral Co(II), Mn(II) and Ni(II) complexes have been synthesized with a tridentate ONC-donor hydrazone ligand 5‑chloro-3-(2-(2,4-dinitrophenyl)hydrazono)indolin-2-one (H2L). The chemical structures of the complexes were elucidated by spectroscopic methods. The spectral data show an octahedral geometry where a cyclometallation was formed through deprotonation of the 6-C-H carbon of the 2,4-dinitrophenyl ring with O and azomethine N coordinating to the metal atom. DFT calculations were used to investigate the structures and the electronic properties of the complexes and their optimized structures were generated. Molecular docking studies on the transmissible gastroenteritis virus protease (4F49) and the COVID-19 main protease (6LU7) revealed that Ni(II) complex displayed the highest binding affinity (-9.7 kcal/mol and -8.2 kcal/mol) to the active site of proteins 4F49 and 6LU7 respectively. The protein-complex interactions studied for all the compounds exhibit favourable binding affinities, surpassing the -5.0 kcal/mol threshold reported in the literature. These studies indicate that Ni(II), Co(II) and Mn(II) cyclometallated complexes of the hydrazone ligand are potential inhibitors of SARS-CoV-2 and the gastroenteritis virus.