Framework and catalytic activity of a metallomicelle system made from an azacrown ether, lanthanum(III) ion and a cationic surfactant

摘要

A metallomicelle system comprising an azacrown ether, lanthanum(III) ion and a cationic surfactant was constructed and used as catalyst in the hydrolysis of bis(4-nitrophenyl) phosphate ester (BNPP). The interaction between La(III) and the azacrown ether, and the resulting complex and BNPP, were analysed by fluorescence spectroscopy. The catalytic rate of BNPP hydrolysis was measured kinetically by UV-Vis spectrophotometry. The results indicated that the metallomicelle system exhibited relatively high stability and excellent catalytic function in BNPP hydrolysis, the rate of which, compared with the spontaneous hydrolysis, increased by a factor of ca 2 × 10~7 due to the catalytic effect of the active species and the local concentration effect of the micelle in the metallomicellar system. The results also showed that the complex, comprising La(III) ion, and the azacrown ether, is the active catalytic species, while the micelles provide a useful catalytic environment for reaction. On the basis of these results, a reaction mechanism for the catalytic hydrolysis of BNPP is proposed.