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 Ni^II synthetic hydrolase [Ni₂(HBPPAMFF)­(μ-OAc)₂(H₂O)]­BPh₄ (<b>1</b>) (H₂BPPAMFF = 2-[(<i>N</i>-benzyl-<i>N</i>-2-pyridylmethylamine)]-4-methyl-6-[<i>N</i>-(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 Ni^II complex covalently attached to the silica surfaces was fully characterized by different techniques. The catalytic turnover number (<i>k</i>_cat) of the immobilized Ni^IINi^II 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 (<i>E</i> = <i>k</i>_cat/<i>K</i>_M) and the supported catalyst can be reused for subsequent diester hydrolysis reactions