Jia-qing Xie

Kinetic Study of the Hydrolysis of BNPP by the Cerium(III) Complex

5,5,7,12,12,14-Hexamethyl-1,4,8,11-tetraazacyclotetradecane (L) was synthesized and characterized. The kinetics of hydrolysis of bis(p-nitrophenyl)phosphate (BNPP) in the catalytic system containing macrocyclic ligand and cerium(III) was investigated. This catalytic system show high catalytic activity and better reproducibility and stability than other similar systems in the range of pH of around 5.6–7.2. The stoichiometry and spectral analysis showed that the real active species is the macrocyclic complex of cerium(III). Based on the analytical results of the specific absorption spectra, an intramolecular nucleophilic substitution mechanism for the catalytic hydrolysis of BNPP is proposed, a correlative kinetic mathematical model is established, and the corresponding thermodynamic and kinetic constants are calculated.

Studies on the Phenol Oxidation with H2O2 Catalyzed by Metallomicelle Made from Crowned Schiff Base Mn(III) Complexes

Metallomicelles made from two Schiff base manganese(III) complexes (MnL1 and MnL2) and surfactants (CTAB and Brij35) were used as mimetic peroxidase in the catalytic oxidation of phenol by H2O2. The catalytic activity of the complexes (MnL1 and MnL2) were investigated. The mechanism and a kinetic mathematic model of the phenol catalytic oxidation were also studied. The results show the optimum acidity of the enzyme-like system in the paper is ca. pH 7.0, the optimum temperature which is ca. 35°C and the optimum molar ratio of H2O2 to the complex is ca. 30 in the complexes-H2O2-buffered solution; the Schiff base manganese(III) complexes and their metallomicelles as peroxidase mimics exhibit good catalytic activity and similar catalytic character to natural enzyme.

studies of DNA binding and DAN cutting mechanism of an azamacrocyclic cerium complex with carboxyl branch

An azamacrocyclic compound with a carboxyl branch, 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclo-tetradecane-N/-acetic acid (L), and its cerium complex were synthesised and characterised. The mode of combination of the cerium complex with DNA was investigated by fluorescence and UV-Vis absorption spectroscopy. The cutting function of the cerium complex towards supercoiled DNA was studied by the gel electrophoresis method. The results show that metal complex can bind to the phosphate group of DNA double helix and promote the hydrolysis of the phosphodiester bond of supercoiled DNA (Form I); under certain conditions, supercoiled form DNA (Form I) was transformed into the nicked form DNA (Form II) under the strong cutting effect of the macrocyclic cerium complex; the cutting is completed by a hydrolysis mechanism.

Catalytic mechanism and activity of a nitrogen heterocycle lanthanum(III) complex in the hydrolysis of bis(4-nitrophenyl) phosphate ester

The system made up of a nitrogen heterocycle ligand and lanthanum(III) ion was used in the catalytic hydrolysis of bis(4-nitrophenyl) phosphate ester (BNPP). This catalytic system showed higher catalytic activity in this hydrolysis and better reproducibility and stability than other similar lanthanum(III) ion systems. The rate of the catalytic hydrolysis was about 108-fold faster than that of its spontaneous hydrolysis under the same conditions. Compared with previous Cu(II) or Ni(II) complexes containing the same ligand in water, the activity of the macrocyclic La(III) complexe is increased ca 104-fold. The experimental evidence showed that the mon-hydroxy complex made of the nitrogen heterocycle ligand and lanthanum(III) ion is the active species as catalyst in the catalytic hydrolysis of BNPP.

The catalytic oxidation of aqueous phenol by H 2 O 2 using a macrocyclic (N-donor) cobalt(II) complex

A new macrocyclic (N-donor) cobalt(II) complex, denoted CoR, was synthesized and characterized, and used as a mimetic peroxidase in the catalytic oxidation of phenol by H2O2. The catalytic system displayed high catalytic activity and the catalytic character of a metalloenzyme, although it did not attain the catalytic efficiency of enzymes. The final products were maleic and oxalic acids. Intermediate products, such as catechol and hydroquinone and p-benzoquinone, were detected by high-pressure liquid chromatography (HPLC) and UV-Vis spectrophotometry. The effects of temperature and the pH of the system on the rate of the catalytic oxidation were investigated. A reaction mechanism and kinetic model for the catalytic oxidation are proposed, which are supported by the results of the experimental and calculation data.

Kinetic Study on p-Nitrophenyl Picolinate Hydrolysis Promoted by the Complex Bis(O,O′-di(2-Benzyl)Dithiophosphato)Nickel(II)

The complex Ni[S2P(OCH2Ph)2]2 (MR) was synthesised and characterised by elemental analysis, IR spectroscopy and 1H NMR spectroscopy. The hydrolysis of p-nitrophenyl picolinate (PNPP) as promoted by this complex was investigated by the UV-vis method, the results showing that MR acts as a very efficient catalyst. The specific absorption spectra of the hydrolytic reaction systems indicated that the key intermediate, made up of PNPP and MR was formed during reaction. Based on these spectra, a mechanism for the catalytic hydrolysis of PNPP has been proposed and a kinetic mathematical model established.