1-(3-Chlorophenyl)-4-(3-phenylseleno propyl) piperazine (L); synthesis, spectroscopic characterization, DFT studies, antimicrobial evaluation and its reactivity toward group 12 metal chlorides

C₆H₅Se⁻Na⁺ (generated in situ by NaBH₄ reduction of (C₆H₅Se)₂) on reaction with ClC₃H₆C₄H₈N₂ClC₆H₅ under N₂ atmosphere results in C₆H₅SeC₃H₆C₄H₈N₂ClC₆H₅ (L) as a cream-colored solid. Its 1:1 metal complexes having the general formula [MLX₂], where M = Zn, Cd, Hg, and X = Cl, have been prepared. Ligand L and its complexes 1–3 are characterized on the basis of physico-chemical and spectral (FT-IR, ESI Mass, ¹H, ¹³C, DEPT 135° ¹³C {¹H}, and ⁷⁷Se{¹H} NMR) studies. IR spectroscopy revealed that L is coordinated solely through selenium and nitrogen to zinc, cadmium, and mercury ions forming a six-membered chelate ring around M(II) ions. Elemental analysis measurements along with ¹H, ¹³C, DEPT 135° ¹³C {¹H}, and ESI-mass data also confirm the bidentate coordination mode of the ligand. Moreover, the coordination from selenium atom is also supported by the downfield shift of signal in ⁷⁷Se{¹H} NMR spectroscopy. Using DFT-based optimization of structures, the HOMO-LUMO energy gaps and molecular electrostatic potential surface of ligand L and complexes 1–3 were theoretically calculated at the B3LYP/LANL2DZ level of theory. Ligand L and complexes 1–3 display significant antibacterial and antifungal activity.