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

Reactions between 3-amine-2-((pyridin-2-ylmethyl)selanyl)pyridine ( L ) and MX 2 (M = Co, Cu, Zn; X = Cl, Br) result in the formation of the metal( ii ) molecular complexes 1-5 with the general formula [MX 2 ( 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 [ReOCl 3 (PPh 3 ) 2 ] as precursor. Firstly, the formation of 6 was observed in the mother liquor, through C sp 3 -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 [ReOCl 3 (PPh 3 ) 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 [CoCl 2 ( L )] ( 1 ), [CuCl 2 ( L )] ( 3 ), [CuBr 2 ( L )] ( 4 ) and, [ZnCl 2 ( L )] ( 5 ) possess significant bactericidal activity when compared with those of the free ligand and metal salts used in the synthesis. New coordination compounds bearing 2-pyridylselenium and d -block metals were synthesized and structurally characterized. The complexes showed antibacterial activity against Staphylococcus aureus and Escherichia coli.