Synthesis, characterization, and anticancer evaluation of nano-sized schiff base metal chelates

Nano-sized bivalent metal chelates of thiophene-thiol Schiff's base Zn(II), Cu(II), Ni(II), and Co(II) were investigated by spectroscopic methods and quantum mechanical calculations. These chelates adopt the overall formula [M(TTSB)₂], given that TTSB = [4-methyl-2-((E)-((2-(((E)-thiophen-2-ylmethylene)amino)phenyl)imino)methyl)-benzenethiol] (C₁₉H₁₆N₂S₂), M = Cu(II), Ni(II), Co(II), and Zn(II). Quantum chemical calculations were used to supplement the experimental investigations. The [Zn(TTSB)2] chelate with a small energy gap value ∆E (0.900 eV) is more reactive than all other chelates, according to DFT simulations that examined ∆E for molecules in LUMO and HOMO. The tridentate NNS donor Schiff base and the metal ions (II) created three coordination bonds, which produced chelates with an octahedral geometry. The bivalent metal chelates' high-resolution TEM and X-ray diffraction (XRD) data demonstrated that the particles were nanometric in size and distributed uniformly across the chelates ' surfaces. Nano-sized metal (II) chelates exhibit higher viscosity than thiophene-thiol Schiff's base ligand (TTSB). Every synthetic molecule has undergone screening for antibacterial activity in vitro. The reference standard and test drugs' minimum inhibitory concentrations (MICs) were established. Excellent action against Candida albicans has been demonstrated by ligand, Cu(II), and Zn(II) chelates. The cytotoxicity of TTSB ligand and its chelates against HePG2 (human liver cancer cell line) and MCF-7 (Humanbreast adenocarcinoma cell line) was evaluated by the MTT assay for 24 h. The cytotoxicity experiments against HePG2 showed the order: [Zn(TTSB)₂] > [Cu(TTSB)₂] > [Co(TTSB)₂] > [Ni(TTSB)₂] > TTSB. Furthermore, biological investigations revealed that chelate Zn(II) induced apoptosis and halted the cell cycle at the G1 phase in HePG2 cancer cells. Notably, after 24 h, Zn(II) chelate significantly elevated reactive oxygen species (ROS) levels, suggesting a potential mechanism for its anticancer effects. To monitor Zn(II) chelate distribution within HePG2 cells, researchers employed confocal laser scanning microscopy. The findings demonstrated that Zn(II) chelate specifically localized to lysosomes, leading to lysosomal dysfunction.