Study on kinetics and mechanism of mononuclear rare earth metal complexes in promoting the hydrolysis of 2-hydroxy-propyl-p-nitrophenyl phosphate (HPNP)

• DOI: 10.1016/j.molcata.2006.11.033
• Publication Date: 2006-11-30T10:14:48Z
• Authors: Qiang Liu; Huamei Chen; Hai Lin; Huakuan Lin
• Keywords: 01 natural sciences; 0104 chemical sciences

Abstract Two novel tripodal ligands, N , N ′, N ″-tri-(3′-phenylpropionic acid-2′-yl)-1,3,5-tri-aminomethylbenzene (L1), N , N ′, N ″-tri-(4′-methylvaleric acid-2′-yl)-1,3,5-triamino-methylbenzene (L2) have been synthesized. The hydrolytic kinetics of 2-hydroxy-propyl- p -nitrophenyl phosphate (HPNP) catalyzed by complexes of L1, and L2 with La(III) and Gd(III) have been studied in aqueous solution at 298 K, I = 0.10 mol dm −3 KNO 3 at pH 6.7–8.2, respectively. GdL2 has the best catalytic effect in the four complexes for hydrolysis of HPNP. Its k LnLH−1 , k LnL and p K a are 0.0927 mol −1 dm 3 s −1 , 0.000101 mol −1 dm 3 s −1 and 7.73, respectively. Due to smaller radius of Gd(III) compared with that of La(III), its complexes have lower p K a and better catalytic ability compared with corresponding La(III) complexes. This paper expounds the result from the structure of the ligands and the properties of the metal ions, and deduces the catalysis mechanism.