Phenolate-bridged zinc(II) complexes relevant to biological phosphoester cleavage

Three zinc complexes based on 2,6-bis(N-2-pyridylmethyl)formimidoyl-4-methylphenolate (HL) by employing Zn(ClO4)2, Zn(CH3COO)2, and ZnCl2 have been synthesized and investigated as functional models of phosphoesterases. The molecular structure of [{Zn2L(µ 3-OH)(H2O)}2](ClO4)4 (1) obtained by reacting zinc perchlorate with HL was determined by X-ray diffraction analysis, revealing a tetranuclear species with four zinc centers and two ligands. Two zinc ions are accommodated within the two compartments of each ligand and are bridged by an additional hydroxide leading to Zn–Zn distances of 3.1235(9) and 3.1268(9) A, respectively. The hydroxide is involved in an additional bridge to the second LZn2 moiety forming a µ 3-OH. A water molecule is coordinated to two of the four zinc ions. The occurrence of a hydroxide group and of a coordinated water is relevant to the structure found in the native enzyme. The hydrolysis of the phosphoester bis(p-nitrophenol)phosphate ester (BNPP) in a mixture of DMSO and water at 5...