Synthesis and Characterization of Novel Hydrazone Complexes: Exploring DNA/BSA Binding and Antimicrobial Potential

Research involving coordination chemistry with Schiff base hydrazones finds applications in various areas, particularly in bioinorganic chemistry and biomedicine. This work aims to contribute to this field by employing the ligand (E)-2-((2-(benzothiazol-2-yl)hydrazone)methyl)phenol (H₂L), synthesized via a condensation reaction with salicylic aldehyde. The ligand was isolated, characterized, and subsequently complexed with nickel(II) chloride and copper(II) nitrate, yielding three new crystalline complexes: [Ni(HL)₂] (<b>1</b>), [Ni₂(L)₂(Py)₂(EtOH)]·DMF·0.5H₂O (<b>2</b>), and [Cu₃(L^#)₂(DMF)₂] (<b>3</b>) (where Py = pyridine). The metal complexes were structurally characterized using IR, UV-vis, TGA-DSC, and SCXRD techniques. These analyses confirmed the coordination of the ligand to the metal center via nitrogen and oxygen donor atoms, establishing the formation of mono-, bi-, and trinuclear complexes, respectively. DNA interaction studies were performed through spectroscopic titration and viscosity measurements, indicating that the complexes interact via an intercalative mode, with the interaction order being <b>3</b> > <b>2</b>> <b>1</b>. Partition coefficient analysis revealed that complexes <b>1</b> and <b>3</b> have a greater tendency to partition into the organic phase, suggesting their potential to cross lipid membranes, while complex <b>2</b> and the ligand are more hydrophilic. Fluorescence-based BSA binding studies demonstrated interactions between the complexes and the biomolecule, following the same order as observed in the DNA interaction. Biological tests showed that the ligand lacked antimicrobial and antiyeast activity, while the metal complexes are biologically active. Notably, the copper complex displayed the strongest antibacterial effect, likely due to copper's essential biological role.