title: Rapid hydrolysis of phosphate ester promoted by Ce(IV) conjugating with a β-cyclodextrin monomer and dimer.
abstract: Two N-donor ligands (L(1) and L(2)) derived from a β-cyclodextrin (βCD) monomer and dimer were employed to mediate the hydrolytic activity and stability of the Ce(IV) ion in aqueous solution. Complexes Ce(IV)-L(1) and Ce(IV)-L(2) were prepared in situ and characterized by means of UV-vis and NMR measurements. Ce(IV)-L(1) catalyzed the hydrolysis of a DNA model, bis(4-nitrophenyl)phosphate (BNPP) with k(cat) = 5.2 × 10(-3) s(-1) (half-life t(1/2) ≈ 2 minutes) under mild conditions, which represented an approximate 130 million-fold acceleration with respect to the spontaneous hydrolysis of BNPP. The dinuclear species, [Ce(2)L(1)(2)(OH)(5)](3+), contributed splendidly to the catalytic efficiency which echoed the active species postulation of [Ce(2)(OH)(7)](+) in the literature. Ce(IV)-L(2) exhibited efficient binding with BNPP giving 1/K(M) = 2.1 × 10(5) M(-1) which exceeded other Ce(IV) species, e.g. [Ce(4)(OH)(15)](+), by 2 orders of magnitude, which highlighted the hydrophobicity effect of βCDs. Such a highly binding affinity leads to the second-order rate constant, k(cat)/K(M) = 2.3 × 10(2) M(-1) s(-1), which probably ranks as the highest in the non-enzymatic cleavage of BNPP under similar conditions. Additionally, Ce(IV)-L(2) showed favorable tolerance to basic aqua owing to the bulky protection of double βCD pendants.
authors.affiliation: MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry and Chemical Engineering, Sun Yat-Sen University, Guangzhou 510275, China.
authors.forename: Meng
authors.initials: M
authors.lastname: Zhao
authors.forename: Cong
authors.initials: C
authors.lastname: Zhao
authors.forename: Xue-Qin
authors.initials: XQ
authors.lastname: Jiang
authors.forename: Liang-Nian
authors.initials: LN
authors.lastname: Ji
authors.forename: Zong-Wan
authors.initials: ZW
authors.lastname: Mao
mesh_terms: D002384:Catalysis; D002563:Cerium / Q000737:chemistry*; D019281:Dimerization; D004950:Esterases / Q000737:chemistry; D006868:Hydrolysis; D007700:Kinetics; D009596:Nitrophenols / Q000737:chemistry*; D013816:Thermodynamics; D047392:beta-Cyclodextrins / Q000737:chemistry*
chemical_list: D009596:Nitrophenols; D047392:beta-Cyclodextrins; D002563:Cerium; C002887:bis(4-nitrophenyl)phosphate; D004950:Esterases; C031215:betadex