Synthesis and charactrization of Imidazole Model Complexes of Inhibited Hydrolases

Abstract

Previous studies in this work showed that model dinuclear hydrolases of the general formula [M2(m-H2O)(OAc)4(tmen)2]; where, M= Mn (Mn), Co, Ni reacted with hydroxamic acids to give a wide range of some hydroxamate bridged complexes whose structures mimic closely observed inhibited ureases. In veiw of the frequent occurrence of histidine as a ligating molecule in many metalloenzymes inlikely the hydrolases, it was decided to investigate the chemistry of a series of imidazole complexes analogous to the above models based on tmen as capping ligand.Model dinuclear hydrolases [M2(m-H2O)(OAc)4(Im)4]; M= Ni (1), (2) and Co (3), prepared and fully characterized. Reaction of mono- and dihydroxamic acids with the model dinuclear hydrolases prepared above gave a wide range of some hydroxamate bridged complexes whose structures mimic closely observed inhibited ureases. For example, reaction of a monohydroxamic acid such as N-phenylacetohydroxamic acid [CH3C(=O)NC6H5OH], (N-PhAHA) with the dimeric complex [Ni2(H2O)(OAc)4(Im)4] gave the dark/green complex. [Ni2(OAc)(N-phAA)2(Im)4][OAc].2H2O and reaction of a dihydroxamic acid such as glutarodihydroxamic acid [(CH2)3{C(=O)NHOH}2.H2O],  (GluH2A2) with the dimeric complex [Ni2(H2O)(OAc)4(Im)4] gave a Blue/green crystals of [Ni2(OAc){C(=O)N(O)(CH2)3C(=O)}(Im)4][OTF]2.In general, the above series based on the imidazole ligand was found to be suscceptable to easy dissociation in polar solvents such as methanol as approved by spectroscopic studies (IR, NMR, C.H.N. , elementary analysis and X-ray crystallography).