Molecular, Stochiometric, Stability and Biological Investigations of Novel Multifunctional Salen Metal Chelates: From Synthesis to Therapeutic Potential Supported by Theoretical Approaches

ABSTRACT

Three novel complexes comprising a 2,6‐bis((E)‐1‐(2‐(4‐bromophenyl)hydrazono)ethyl)pyridine (BPHE) ligand with Pd^II, Zn^II, and VO^II metal centers have been synthesized and thoroughly characterized using FT‐IR, mass spectrometry, UV–vis spectroscopy, thermogravimetric analysis, and conductivity measurement data. The thermodynamic and kinetic aspects of their thermal degradation phases have been evaluated. Conductivity measurements confirmed that all the chelates exhibited electrolytic behavior where BPHEPd (60.50 Ω⁻¹ cm² mol⁻¹), BPHEZn (58.40 Ω⁻¹ cm² mol⁻¹), and BPHEV (94.21 Ω⁻¹ cm2 mol⁻¹). Based on stability and stoichiometry measurements, the BPHE ligand operates as a tridentate donor, bonding to Pd(II) in a diamagnetic square planar configuration, Zn(II) in a diamagnetic tetrahedral arrangement, and VO(II) in a square pyramidal geometry with a magnetic moment of 1.79 B.M. Also, the stability and formation constants of the investigated complexes were determined and follow the order of BPHEV > BPHEPd > BPHEZn complexes. The pH profile revealed that the wide range of pH stability of the tested complexes (pH = 4–11). To delve into the reactivity and potential biomedical implications of these metal complexes, we performed density functional theory (DFT) computations under gas‐phase conditions utilizing the B3LYP/6‐311g(d,p)/LANL2DZ methodology. The antimicrobial efficacy of BPHE and its corresponding complexes was then assessed in vitro against various strains of bacteria and fungi. Notably, the ligand exhibited minimal antimicrobial activity. However, the metal complexes formed with Pd^II displayed substantial antimicrobial potency (43.52 ± 0.15 and 37.20 ± 0.08) mm against M. luteus bacteria and Candida albicans fungi, respectively. The anti‐cancer potential of these substances was also scrutinized through in vitro assays, revealing a dose‐dependent decrease in the viability of the evaluated cancerous cell lines. The high cytotoxicity was clearly recorded for the BPHEPd complex with IC₅₀% (3.62 μg/mL) against the MCF‐7 cell line. In the realm of antioxidant capabilities, the complexes were subjected to in vitro analysis, which affirmed that the Pd^II complex had the highest free radical scavenging capacity among them with an IC₅₀ value of 15.12 μg/mL, surpassing that of ascorbic acid, which served as the benchmark.