Cd(II) and Zn(II) complexes with 2-mercaptopyridine: Synthesis, crystal structure, Hirshfeld surface analysis, luminescent properties, aggregation behaviours, current-voltage characteristic and antibacterial assay

Two transition metal complexes viz. [Cd(2-mcpH)4](NO3)2 (1) and [Zn(2-mcpH)4](NO3)2 (2) were synthesized by the reaction of cadmium(II) nitrate tetrahydrate or zinc(II) nitrate hexahydrate with 2-mercaptopyridine (2-mcpH) in 1:4 M ratio. These complexes have been fully characterized by UV-Vis, IR, NMR-spectroscopy and Single crystal X-ray analysis. Luminescent properties of complex 2 were also investigated. The emission seen in complex 2 is accredited due to the pi...pi* intra-ligand transitions. The structural architecture of both complexes manifested as monomeric tetra-coordinated M-centers, each adeptly coordinated by four 2-mcpH ligands. These arrangements effectively neutralized the complex charge, employing two nitrate groups. Concurrently, Hirshfeld surfaces analysis showed maximum interactions of 25.6%, 26.6% for H...H, and 25.0%, 25.1% for O...H contacts in complexes 1 and 2, respectively. In current-voltage (I-V) characteristic studies, it has been observed that both complexes showed Ohmic behavior. FESEM studies give convincing visual facts of the aggregation behaviour of two complexes. To appraise their potential, the ligand and complexes were subjected to antibacterial s. Complex 1 showed the most potent antibacterial effect, particularly against Gram-negative bacteria, while complex 2 exhibited a moderate effect against both Gram-negative and Gram-positive bacteria.