Ni(II) and Co(II) binary and ternary complexes of 3-formylchromone: spectroscopic characterization, antimicrobial activities, docking and modeling studies

Reactions of 3-formylchromone (L) with Ni(ii) and Co(ii) ions having different anions (acetate, perchlorate, nitrate, and chloride) yielded a series of binary and ternary octahedral complexes with the general formula [ML(n)L′(m)X(y)(S)(a)]Z(y)·bS, where M = Ni or Co, n = 1–3, L′ = auxiliary ligand = 8-hydroxyquinoline or 1,10-phenanthroline, m = 1 or 2, X = acetate or chloride, y = 0 or 2, S = H(2)O or MeOH, a = 0–2, Z = nitrate or perchlorate and b = 0–1.5. Elemental and thermal analyses and infra-red, electronic, mass, magnetic susceptibility and molar conductivity measurements were successfully utilized to characterize the structures of the chromone complexes. The chromone ligand acts as a neutral bidentate ligand through its formyl and γ-pyrone oxygen atoms. The obtained complexes were formed with molar ratios 1 : 2 and 1 : 3 M : L for the binary and 1 : 2 : 1 and 1 : 1 : 1 M : L : L′ for the ternary complexes. The kinetic parameters of the thermal degradation steps were estimated and explained using the Coats–Redfern equations. The synthesized complexes showed antimicrobial activity with higher activity toward Candida albicans and Bacillus subtilis. Docking studies showed good agreement with the antimicrobial activity. Molecular modeling of the synthesized complexes was performed using Hyperchem at the PM3 level and the calculated structures correlate with the experimental data.