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

✍ Scribed by Qiang Liu; Huamei Chen; Hai Lin; Huakuan Lin

• Publisher: Elsevier Science
• Year: 2007
• Tongue: English
• Weight: 548 KB
• Volume: 269
• Category: Article
• ISSN: 1381-1169
• DOI: 10.1016/j.molcata.2006.11.033

✦ Synopsis

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 pK 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 pK 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.