Phosphate ester hydrolysis catalyzed by a dinuclear cobalt(II) complex equipped with intramolecular β-cyclodextrins

• A dinuclear Co(II) complex, Co2L, coupling to β-CDs was synthesized and characterized.
• Supramolecular effect protects the dinuclear Co(II) center from oxidation in air.
• High activity toward bis(4-nitrophenyl) phosphate hydrolysis was observed at neutral pH.
• Metal effect was discussed by comparing the analogous Zn2L, Cu2L and Co2L.
• Unexpected phosphotase-like activity was observed for Co2L.

Dinuclear metallohydrolases are ubiquitously involved in biological transformations. For understanding and application purpose, significant efforts have been dedicated to the structural or/and functional mimics. Herein, a dinuclear Co(II) complex, Co2L, with intramolecular β-CDs is presented. The β-CDs confine a hydrophobic microenvironment that contributes to the valence stability of the ligated Co(II) ions. Species of Co2L in aqueous solution is clarified according to the results of potentiometric titration and UV–vis titration experiments. A highly positive-charged species [Co2HL]4+ is present at quasi-neutral condition, which contributed significantly to the binding and activity toward bis(4-nitrophenyl) phosphate (BNPP) assisted by the hydrophobic interactions exerted by intramolecular β-CDs. The kcat/KM value of Co2L is determined to be 9.8 × 10−2 M−1 s−1 at pH 6.5 and 308 K, which exceeds that of the reported zinc analog (Zn2L) by three orders of magnitude. Unexpectedly, Co2L also catalyzes hydrolysis of a phosphate monoester, 4-nitrophenyl phosphate (NPP). The observed phosphate esterase activities are rarely reported among synthetic Co(II) complexes.

A dinuclear Co(II) complex equipped with intramolecular β-CDs effectively catalyzed the hydrolysis of phosphate esters. Metal effect is discussed.Figure optionsDownload high-quality image (136 K)Download as PowerPoint slide