Synthesis, Characterization, DNA, Fluorescence, Molecular Docking, and Antimicrobial Evaluation of Novel Pd(II) Complex Containing O, S Donor Schiff Base Ligand and Azole Derivative

Pd(II) with the Schiff base ligand 2-Hydroxy-3-Methoxy Benzaldehyde-Thiosemicarbazone (HMBATSC) (L2) and 2-aminobenzothiazole (2-ABZ) (L1) was synthesized. The Schiff base ligand and the Palladium(II) complex were characterized by C.H.N.S, FT-IR, conductance studies, magnetic susceptibility, XRD, and TGA. From the elemental analysis and spectral data, the complex was proposed to have the formula [Pd(HMBATSC)(2-ABZ)H2O]. The interaction between the Pd(II) complex and DNA was examined through various methods, including UV–Vis spectroscopy, fluorescence techniques, and DNA viscosity titrations. The findings provided strong evidence that the interaction between the Pd(II) complex and DNA occurs through the intercalation mode. The analysis yielded the following values: a Stern–Volmer quenching constant (ksv) of 1.67 × 104 M−1, a quenching rate constant (kq) of 8.35 × 1011 M−1 s−1, a binding constant (kb) of 5.20 × 105 M−1, and a number of binding the sites (n) of 1.392. DFT studies suggest that the azole derivative may act as an electron donor through pyridine nitrogen, while the Schiff base ligand may act as an electron donor via oxygen and sulfur atoms. TDDFT calculations indicate that the intramolecular charge transfer from the Schiff base to Pd(II) is responsible for the complex’s fluorescence quenching. The powder X-ray diffraction data revealed that the complex is arranged in a monoclinic system. The resulting Pd(II) complex was investigated for its antimicrobial activity and demonstrated antibacterial efficiency. Interestingly, it showed potent activity against E. coli and E. niger that was found to be more powerful than that recorded for Neomycin.