Journal of Colloid and Interface Science 247, 366–371 (2002) doi:10.1006/jcis.2001.8069, available online at http://www.idealibrary.com on Metallomicellar Catalysis: Catalytic Cleavage of p-Nitrophenyl Picolinate by Cu 2+ Complex of 4-Chloride-2,6-bis(N-hydroxyethylaminomethyl)- benzophenol in Micellar Solution Xiang Yan, ∗, † Jiang Bingying, ∗ Zeng Xiancheng, ∗,1 and Xie Jiaqing ∗ ∗ Department of Chemistry, Sichuan University, Chengdu 610064, People’s Republic of China; and †Department of Environment Engineering, Beijing University of Aeronautics & Astroautics, Beijing 100083, People’s Republic of China Received May 17, 2001; accepted October 29, 2001; published online February 5, 2002 The hydrolysis of p-nitrophenyl picolinate (PNPP) catalyzed by the Cu(II) complex of 4-chloride-2,6-bis( N-hydroxyethyl- aminomethyl)-benzophenol was investigated kinetically by observ- ing the rates of release of p-nitrophenol in the presence of three surfactants, which are hexadecyltrimethylammonium bromide, n- lauroylsarcosine sodium, and polyoxyethylene(23) lauryl ether, at different pH and 25 ◦ C. The scheme for the reaction involving a ternary complex comprising ligand, metal ion, and substrate in a micelle was established, and the relative kinetic and thermodynamic parameters were determined, including first-order rate constant (k N ), association constant ( K s ) for ternary complex, and pK a for the hydroxide ion of the ternary complex. The reaction mechanism was discussed. C  2002 Elsevier Science (USA) Key Words: catalysis; metallomicelle; kinetic; hydrolysis of p- nitrophenyl picolinate. INTRODUCTION It is well established that the rates and pathways of all kinds of chemical reactions can be altered in many cases by perform- ing the reactions in micellar media instead of pure bulk sol- vents. Micelles can concentrate the reactants within their small volumes (1–4); stabilize substrates, intermediates, or products (5, 6); and orient substrates (7–9) so that ionization potential and oxidation–reduction properties, dissociation constants, physi- cal properties, quantum efficiencies, and reactivity are changed (10–12). Thus micelles can also alter the reaction rate, mecha- nism (13), and regio- and stereochemistry (14, 15). On the basis of these important characteristics, micellar catalysis has been extensively studied in past decades as a model of enzyme catal- ysis of the cleavage of esters and amides, deacylation, etc., and surprising catalytic efficiency has been observed: for many re- actions rate increases of 5- to 100-fold over those of reactions in homogeneous solutions, even on the order of 10 6 -fold (16–21). 1 To whom correspondence should be addressed at Department of Chemistry, Box 74, Sichuan University, Chengdu, Sichuan 610064, People’s Republic of China. E-mail: zengxc@prinds.scu.edu.cn. Although the evident rate enhancement of reactions has been provided in micellar medium through the concentration and medium effect which imitate the hydrophobic microenviron- ment of natural hydrolases to an extent, this cannot mimic the active sites of hydrolases in which metal ions play an important role. So in recent years, the attention on artificial enzyme de- signers was focused, in particular, on metallomicellar catalysis, which is made up of transition metal complexes and surfac- tants (22, 23). As a new artificial enzyme model, metallomicel- lar catalysis not only may provide a hydrophobic microenviron- ment for hydrolysis of carboxylic and phosphoric acid esters and amide, but may also mimic enzyme active sites with the hydrox- yls properly bound to the ligand activated by metal ions, which act as effective nucleophiles in neutral aqueous media (24–26). In our previous works, D-glucosamine Schiff base metal complexes (27) and the binuclear metal complex coordinating tripeptide (28, 29), as catalysts to catalyze hydrolysis of car- boxylic acid esters, have been studied kinetically in the presence of hexadecyltrimethylammonium bromide, and satisfactory rate acceleration results were obtained. To better understand the effects of different metallomicelles formed from different kinds of surfactants and a fixed metal com- plex on hydrolysis of PNPP, we prepared the Cu 2+ complex of 4-chloride-2,6-bis( N -hydroxyethylaminomethyl)-benzophenol 1. Kinetic behavior was determined respectively in the presence of three surfactants: were hexadecyltrimethylammonium bromide (CTAB), n-lauroylsarcosine sodium (LSS), and poly- oxyethylene(23) lauryl ether (Brij 35). The quantitative treat- ment of metallomicellar catalysis involving a ternary complex with ligand, metal ion, and substrate has been established for 1 catalyzing the hydrolysis of p-nitrophenyl picolinate (PNPP). 366 0021-9797/02 $35.00 C  2002 Elsevier Science (USA) All rights reserved.