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

• Synthesis of two new dinuclear complexes (CuII and ZnII) is reported.
• Structurally characterised complexes were optimized with DFT.
• They were tested for the potency to catalyse phosphate ester hydrolysis.
• Hydrolysis mechanism involves Lewis acid activation.
• Both the complexes show excellent activity.

Present work describes synthesis of dibridged dinuclear [Cu2L2(μ2-NN pyr)(NO3)2(H2O)2] and [Zn2L(μ-OH)(μ-NNpyr)(H2O)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 kcat values in the range of 2 × 10−3s−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.

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