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

Synthesis of a polydentate ligand comprising imidazole donors, 1,3-bis[(4-m ethyl-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-pyramid al coordination geometry with the basal positions occupied by the four nitr ogen atoms of a tetradentate BIPO ligand and the apical position by a water molecule, complexes 2 and 3 exhibit elongated octahedral coordination geom etries with the axial positions occupied by a pair of aqua molecules, where as complex 4 exhibits an elongated octahedral geometry with the axial posit ions occupied by an aqua molecule and a perchlorate oxygen atom. The crysta l structures of the four complexes are discussed in relation to the prefere nce 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 X 10(-2) +/- 0.01, 1.45 X 10(-2) +/- 0.01 and 0.98 X 10(-2) +/- 0.01 M-1 s(-1), respectively. (C) 1999 Elsevier Science Ltd. All rights reserved.