Kinetics and mechanism of promoted hydrolysis of 2-hydroxypropyl-p-nitrophenyl phosphate (HPNP) by complexes of RPAla and RPVal with La(III), Gd(III)

Two multidentate ligands: N,N′-di-(propionic acid-2′-yl-)-2,9-di-aminomethylphenanthroline (L1) and N,N′-di-(3′-methylbutyric acid-2′-yl-)-2,9-di-aminomethylphenanthroline (L2) were synthesized. The hydrolytic kinetics of 2-hydroxypropyl-p-nitrophenyl phosphate (HPNP) catalyzed by complexes of L1 and L2 with La(III), Gd(III) have been studied. Both LnL and LnLH−1 have been examined as catalysis for the hydrolysis of HPNP in aqueous solution at 298 K, I = 0.10 mol dm−3 KNO3 at pH range 7.4–9.1, respectively. Kinetic studies show that both LnL and LnLH−1 have activity, but LnLH−1 is more active than LnL in the hydrolysis reaction of HPNP. The second-order rate constants of hydrolysis of HPNP are kGdL1H−1=0.0466 mol−1 dm3 s−1kGdL1H−1=0.0466 mol−1 dm3 s−1, kGdL1 = 0.000037 mol−1 dm3 s−1 for GdL1H−1 and GdL1, respectively. New mechanism was proposed for the hydrolysis reaction of HPNP catalyzed by LnL and LnLH−1.

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