Pyrazole bridged dinuclear Cu(II) and Zn(II) complexes as phosphatase models: Synthesis and activity

Abstract Present work describes synthesis of dibridged dinuclear [Cu 2 L 2 (μ 2 -NN pyr)(NO 3 ) 2 (H 2 O) 2 ] and [Zn 2 L(μ-OH)(μ-NNpyr)(H 2 O) 2 ] complexes derived from a pyrazole based ligand bis(2-hydroxy-3-methoxybenzylidene)-1H-pyrazole-3,5-dicarbohydrazide. The ligand shows dimeric chelate behaviour towards copper against monomeric for zinc counterpart. Spectroscopic evidences affirm octahedral environment around the metal ions in solution state and non-electrolytic nature of the complexes. Both the complexes are active catalysts towards phosphomonoester hydrolysis with first order k cat values in the range of 2 × 10 −3 s −1 . Zinc complex exhibited promising catalytic efficiency for the hydrolysis. The dinuclear complexes hydrolyse via Lewis acid activation, whereby the phosphate esters are preferentially bound in a bidentate bridging fashion and subsequent nucleophilic attack to release phosphate group.