Synthesis, structures and hydrolytic properties of metal complexes with 1,3-bis[(4-methyl-5-imidazol-1-yl)ethylideneamino]propan-2-ol

Abstract

Synthesis of a polydentate ligand comprising imidazole donors, 1,3-bis[(4-methyl-5-imidazol-1-yl)ethylideneamino]propan-2-ol (BIPO), and its Zn II ( 1), Mn II ( 2), Ni II ( 3) and Cu II ( 4) complexes are reported. Single-crystal structural analysis shows that complex 1 adopts a distorted square-pyramidal coordination geometry with the basal positions occupied by the four nitrogen atoms of a tetradentate BIPO ligand and the apical position by a water molecule, complexes 2 and 3 exhibit elongated octahedral coordination geometries with the axial positions occupied by a pair of aqua molecules, whereas complex 4 exhibits an elongated octahedral geometry with the axial positions occupied by an aqua molecule and a perchlorate oxygen atom. The crystal structures of the four complexes are discussed in relation to the preference of zinc ion in carbonic anhydrase, and suggest that in the presence of nitrogen donor ligands, Zn II has a significant tendency to form a four- or five-coordination. Hydrolysis of 4-nitrophenyl acetate with complexes 1– 3 shows that the k obs for complexes 1, 2 and 3 were 2.74×10 −2± 0.01, 1.45×10 −2± 0.01 and 0.98×10 −2± 0.01 M −1s −1, respectively.