Binding studies of (N-(methylpyridin-2-yl)-amidino-O-methylurea)copper(II) complexes to four nitrogenous bases and 5′-GMP

Abstract

Two copper(II) complexes of N-(methylpyridin-2-yl)-amidino-O-methylurea (L) containing different anions, Cl− (1) and ClO4− (2), were prepared and investigated the nucleobase-binding ability toward adenine (A), cytosine (C), guanine (G) and thymine (T). Eight bound adducts were characterized by elemental analysis, spectroscopic methods (infrared, electrospray ionization mass, diffuse reflectance, UV–Vis and electron spin resonance) and thermal analysis. Results have shown the coordination of one or two nucleobase molecules to the copper(II) center of 1 and 2 through the N(7) adenine, N(3) cytosine, N(7) guanine and O(4) thymine by the replacement of anion ligands. Further investigation on the binding potential of 1 and 2 was carried out towards 5′-guanosine monophosphate (5′-GMP), a DNA model, and have found that the N(7) atom of 5′-GMP can bind to their copper(II) center. These two coordination compounds, which display the similar base-binding capability, exhibit the antibacterial activity against the three bacteria involved in human-food poisoning (Salmonella, Escherichia coli and Campylobacter) with the most potent toward Campylobacter for 1 and Salmonella and E. coli for 2. Such a behavior suggests that differences in the anionic ligands on 1 and 2 slightly influence on their antibacterial properties.