Synthesis, characterization, and antitumor potency of Pd2+, ZrO2+, and VO2+ complexes with tridentate Schiff base: in vitro biological and in-silico insights

Abstract

Schiff base complexes of ZrO²⁺, VO²⁺, and Pd²⁺ have been produced and characterized by IR, TGA, UV/Vis, and 1 H NMR methods, as well as powder X-ray diffraction (XRD), elemental (CHN) analysis, mass spectrometry, conductivity, and magnetic characteristics. Density Functional Theory (DFT) computations applying the Gaussian 09 software were employed to estimate the equilibrium geometry of the ligand and its complexes at the B3LYP level of theory. The 6-311G++(d, p) basis set was used for the C, H, O, N and Br atoms, and lanl2dz for the Pd, V, and Zr atoms. ZrO²⁺ and Pd²⁺ complexes demonstrate diamagnetic behavior, but magnetic susceptibility investigations verify the paramagnetism of the VO²⁺ complex. Based on spectroscopic and magnetic susceptibility studies, the ZrO²⁺and VO²⁺ complexes have square pyramidal geometries, and Pd²⁺ ZrO²⁺ complex has a square planar geometry. All complexes demonstrate strong antimicrobial potency against various bacterial and fungal species. Pd²⁺ > ZrO²⁺ > VO²⁺ > H₂B is the order of antimicrobial effectiveness, revealing the biggest inhibition zone against Gram-negative bacteria by the Pd²⁺ complex. The order of the rise in antifungal capability against A. flavus is Pd²⁺ > ZrO²⁺ > VO²⁺> H₂B. Additionally, the complexes exhibit notable cytotoxicity against cancer cell lines, such as HCT-116, in contrast to Vinblastine. Moreover, these compounds also demonstrate great potential as free radical scavengers. Finally, possible binding mechanisms at the active sites of bacterial and fungal receptors were explored through docking studies.