Supramolecular Diversity, Theoretical Investigation and Antibacterial Activity of Cu, Co and Cd Complexes Based on the Tridentate N,N,O-Schiff Base Ligand Formed In Situ.

The four new complexes, [Cu(HL)(L)Cl] (), [Cu(HL)(L)]∙Cl∙2HO (), [Co(L)]∙Cl () and [Cd(HL)I]∙dmso (), have been prepared by one-pot reactions of the respective chloride or iodide metal salt with a non-aqueous solution of the polydentate Schiff base, HL, resulted from in situ condensation of benzhydrazide and 2-pyridinecarboxaldehyde, while a ligand HL, in case of , has been formed due to the oxidation of 2-pyridinecarboxaldehyde under reaction conditions. The crystallographic analysis revealed that the molecular building units in - are linked together into complex structures by hydrogen bonding, resulting in 1D, 2D and 3D supramolecular architectures for , and , respectively, and the supramolecular trimer for . The electronic structures of - were investigated by the DFT theoretical calculations. The non-covalent interactions in the crystal structures of - were studied by means of the Hirshfeld surface analysis and the QTAIM theory with a special focus on the C-H⋯Cl bonding. From the DFT/DLPNO-CCSD(T) calculations, using a series of charged model {RC-H}⋯Cl assemblies, we propose linear regressions for assessment of the interaction enthalpy (Δ, kcal mol) and the binding energy (BE, kcal mol) between {RC-H} and Cl sites starting from the electron density at the bond critical point ((), a.u.): Δ = -678 × () + 3 and BE = -726 × () + 4. It was also has been found that compounds , and during in vitro screening showed an antibacterial activity toward the nine bacteria species, comprising both Gram-positive and Gram-negative, with MIC values ranging from 156.2 to 625 mg/L. The best results have been obtained against ML.