Design of a Dinuclear Nickel(II) Bioinspired Hydrolase to Bind Covalently to Silica Surfaces: Synthesis, Magnetism, and Reactivity Studies

Presented herein is the design of a dinuclear NiII synthetic hydrolase [Ni2(HBPPAMFF)­(μ-OAc)2(H2O)]­BPh4 (1) (H2BPPAMFF = 2-[(N-benzyl-N-2-pyridylmethylamine)]-4-methyl-6-[N-(2-pyridylmethyl)­aminomethyl)])-4-methyl-6-formylphenol) to be covalently attached to silica surfaces, while maintaining its catalytic activity. An aldehyde-containing ligand (H2BPPAMFF) provides a reactive functional group that can serve as a cross-linking group to bind the complex to an organoalkoxysilane and later to the silica surfaces or directly to amino-modified surfaces. The dinuclear NiII complex covalently attached to the silica surfaces was fully characterized by different techniques. The catalytic turnover number (kcat) of the immobilized NiIINiII catalyst in the hydrolysis of 2,4-bis­(dinitrophenyl)­phosphate is comparable to the homogeneous reaction; however, the catalyst interaction with the support enhanced the substrate to complex association constant, and consequently, the catalytic efficiency (E = kcat/KM) and the supported catalyst can be reused for subsequent diester hydrolysis reactions.