Coordination compounds containing 2-pyridylselenium ligands: synthesis, structural characterization, and antibacterial evaluation

Abstract

Reactions between 3-amine-2-((pyridin-2-ylmethyl)selanyl)pyridine (L) and MX₂ (M = Co, Cu, Zn; X = Cl, Br) result in the formation of the metal(II) molecular complexes 1–5 with the general formula [MX₂(L)]. The organic ligand is coordinated to the metal center through nitrogen atoms of the pyridine rings, without interaction with the selenium atom. The rhenium(V) complex [ReO(apySe)₂]Cl (6) is formed in two different ways, using [ReOCl₃(PPh₃)₂] as precursor. Firstly, the formation of 6 was observed in the mother liquor, through C_sp³–Se bond cleavage of the ligand L and formation of new Re–Se bonds. Secondly, the direct reaction between bis(3-amino-2-pyridyl)diselane (apySe)₂ and [ReOCl₃(PPh₃)₂] gave complex 6 in higher yields. The coordination compounds were characterized by spectroscopic and crystallographic methods. Furthermore, the antibacterial activity of the complexes 1–5 was evaluated against Gram-positive bacteria, Staphylococcus aureus (ATCC® 25923), and Gram-negative bacteria, Escherichia coli (ATCC® 25922). The results suggest that the complexes [CoCl₂(L)] (1), [CuCl₂(L)] (3), [CuBr₂(L)] (4) and, [ZnCl₂(L)] (5) possess significant bactericidal activity when compared with those of the free ligand and metal salts used in the synthesis.