Crystal structure of a copper( II )–famotidine complex and solution studies of the Cu 2+ –famotidine–histidine ternary system

The crystal structure of the complex [CuL][ClO4]2(L = 3-{[2-diaminomethyleneamino)thiazol-4-yl]methylsulfanyl}-N2-sulfamoylpropionamidine, famotidine) has been determined. It provides a full description of the metal binding sites and reveals the impact of metal co-ordination on the conformation of the drug molecule. Even metal ion binding is not able to change some conformational features of famotidine, which could be an important factor biologically. Potentiometric and spectroscopic data were obtained for the ternary species in the Cu2+–famotidine–histidine system and show that famotidine is a very competitive chelating agent even in the presence of the strongly co-ordinating amino acid.