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 1 )(L 2 )Cl] ( 1 ), [Cu(HL 1 )(L 1 )]∙Cl∙2H 2 O ( 2 ), [Co(L 1 ) 2 ]∙Cl ( 3 ) and [Cd(HL 1 )I 2 ]∙dmso ( 4 ), 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 1 , resulted from in situ condensation of benzhydrazide and 2-pyridinecarboxaldehyde, while a ligand HL 2 , in case of 1 , has been formed due to the oxidation of 2-pyridinecarboxaldehyde under reaction conditions. The crystallographic analysis revealed that the molecular building units in 1 - 4 are linked together into complex structures by hydrogen bonding, resulting in 1D, 2D and 3D supramolecular architectures for 1 , 2 and 4 , respectively, and the supramolecular trimer for 3 . The electronic structures of 1 - 4 were investigated by the DFT theoretical calculations. The non-covalent interactions in the crystal structures of 1 - 4 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 {R 3 C-H} 0 ⋯Cl - assemblies, we propose linear regressions for assessment of the interaction enthalpy (Δ H , kcal mol -1 ) and the binding energy (BE, kcal mol -1 ) between {R 3 C-H} 0 and Cl - sites starting from the electron density at the bond critical point ( ρ ( r BCP ), a.u.): Δ H = -678 × ρ ( r ) + 3 and BE = -726 × ρ ( r ) + 4. It was also has been found that compounds 1 , 3 and 4 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 Acinetobacter baumannii M β L.