Synthesis, crystal structure, and BSA binding studies of new Co(II) and Ni(II) complexes of 2-(hydroxymethyl)-1H-imidazole-4,5-dicarboxylate

Abstract Two new complexes [Co(H3hmIDC)2(H2O)2]·3H2O (1) and [Ni(H3hmIDC)2(H2O)2] (2), where H4hmIDC = 2-(hydroxymethyl)-1H-imidazole-4,5-dicarboxylic acid, have been synthesized and characterized by analytical and spectral techniques. X-ray single crystal diffraction shows that both complexes possess mononuclear structure, but the detail structures are different. Complex 1 belongs to triclinic space group P-1, while 2 belongs to the monoclinic space group P21/c. The mechanism of interaction between the complexes and bovine serum albumin (BSA) were examined by fluorescence emission spectra. The results indicated that the fluorescence intensity of BSA was decreased considerably upon the addition of the complexes through a static quenching mechanism with formation of one binding site. The associated changes in enthalpy and entropy indicating that hydrogen bonding and van der Waals forces were the dominant intermolecular forces for BSA-complex 1 binding system, and hydrophobic interactions was the dominant intermolecular forces for BSA-complex 2 binding system. Furthermore, the effects of the complexes upon the conformation of BSA were analyzed using synchronous fluorescence spectrum and the results showed that the interaction of complex 1 or 2 with BSA affected the conformation of tryptophan residue and then affected the conformation of BSA.