Synthesis of Cobalt(III) Complexes Derived from Pyridoxal: Structural Cleavage Evaluations and In Silico Calculations for Biological Targets

Abstract

This study sought to investigate the synthesis of eight complexes constituted by a cobalt(III) (CoIII) metallic center coordinated to two units of iminic ligands LnC (n = 1–4, L1C–L4C), which are derivatives of pyridoxal hydrochloride and anilines with thioether function containing one to four carbons. Depending on the source of the cobalt ion and the addition (or not) of a non-coordinating counterion, complexes with distinct structures may form, being categorized into two series: [CoIII(LnC)(L0C)] (n = 1–4, C1’–C4’) with a LnC ligand and a ligand that has a thiolate function which cleaves the C-S(thioether) bond (L0C) and [CoIII(LnC)2]PF6 (n = 1–4, C1–C4) with two similar units of the same LnC ligand. The occurrence (or not) of cleavage in the eight complexes was observed by elucidating the solid-state structures by single crystal X-ray diffraction. This exciting method allows the synthesis of CoIII complexes without cleaving the C-S bonds from the ligands, thereby not requiring an inert atmosphere in the reaction systems. The synthesized complexes were evaluated by in silico calculations on viable biological targets such as deoxyribonucleic acid, superoxide dismutase enzyme, human serum albumin, and the structural spike glycoprotein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) with the receptor binding domain (RBD) in both up and down conformations without and in complex with the cellular receptor angiotensin-converting enzyme 2 (ACE2). Overall, in silico results suggested that all the inorganic complexes under study are potential anticancer/antiviral agents; however, C4 and C4’ are the best candidates for future in vitro assays.