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

• Published in: Journal of molecular catalysis. A, Chemical Chemical, 2006-11, Vol.259 (1), p.11-16
• Main Authors: Lin, Huakuan, Liu, Qiang, Lin, Hai
• Format: Article
• Language: English
• Subjects: Catalysis; Chemistry; Exact sciences and technology; General and physical chemistry; Hydrolysis; Kinetics; Mechanism; Rare earth; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry
• ISSN: 1381-1169; 1873-314X
• DOI: 10.1016/j.molcata.2006.02.040

Two novel tripodal ligands, N, N′, N″-tri-(3′-phenylpropionic acid-2′-yl-)-1,3,5-triaminomethylbenzene (L1), N, N′, N″-tri-(4′-methylvaleric acid-2′-yl-)-1,3,5-triaminomethylbenzene (L2) have been synthesized. The hydrolytic kinetics of p-nitrophenyl phosphate (NPP) 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. This paper expounds the result from the structure of the ligands and the properties of the metal ions, and deduces the catalysis mechanism. ▪ Two novel tripodal ligands, N, N′, N″-tri-(3′-phenylpropionic acid-2′-yl-)-1,3,5-triaminomethylbenzene (L1), N, N′, N″-tri-(4′-methylvaleric acid-2′-yl-)-1,3,5-triaminomethylbenzene (L2) have been synthesized. The hydrolytic kinetics of p-nitrophenyl phosphate (NPP) 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. In the study it is found that the catalytic effect of GdL2 was the best in the four complexes for hydrolysis of HPNP. Its k LnL H − 1 , k LnL and p K a are 0.0198 mol −1 dm 3 s −1, 0.0000187 mol −1 dm 3 s −1 and 7.76, respectively. This paper expounds the result from the structure of the ligands and the properties of the metal ions, and deduces the catalysis mechanism.