Ester catalytic hydrolysis by a tridentate N,N′,N″-copper bridged cyclodextrin dimer

A new pyridine bridged cyclodextrin dimer mono-copper complex (CuL) was synthesized and characterized. The hydrolysis of carboxylic acid esters, bis(4-nitrophenyl)carbonate (BNPC) and 4-nitrophenyl acetate (NA), and phosphate ester, a DNA model bis(4-nitrophenyl)phosphate (BNPP), promoted by CuL has been investigated. The resulting hydrolysis rate constants showed that CuL had a very high rate of catalysis for BNPC hydrolysis, yielding a 2.73 × 103-fold rate enhancement over uncatalyzed hydrolysis at pH 7.00, compared to only a 78.2-fold rate enhancement for NA hydrolysis. The initial first-order rate constant of catalytic hydrolysis for BNPP was 1.01 × 10−7 s−1 at pH 8.5, 35 °C and 0.1 mM catalyst concentration, about 1260-fold acceleration over uncatalyzed hydrolysis. The second rate constant kBNPP of BNPP hydrolysis promoted by CuL was found to be 5.94 × 10−4 M−1 s−1.

Graphical abstractA new pyridine bridged cyclodextrin dimer copper complex (CuL) was prepared, characterized and demonstrated as a potent catalyst for ester hydrolysis. The cooperative binding action of both hydrophobic cavities with substrate plays an important role on ester cleavage.Figure optionsDownload full-size imageDownload as PowerPoint slideResearch Highlights► Copper complex based on cyclodextrin dimer as ester hydrolysis catalyst. ► The copper complex exhibited high rate for diesters hydrolysis. ► The cooperation of two cavities of CDs plays an important role on ester cleavage.