Hydrolysis of BNPP Catalyzed by the Crowned Schiff Base Co(II) Complex Containing Benzoaza‐15‐Crown‐5 in Micellar Solution

It has been reported that three aza crowned Schiff base cobalt (II) complexes were synthesized and characterized, and the metallomicelle made up of the cobalt (II) complexes and surfactants(Brij35, CTAB, LSS), as mimic hydrolytic metalloenzyme, was used in catalytic hydrolysis of bis(4‐nitrophenyl) phosphate (BNPP). The analysis of specific absorption spectrums of the hydrolytic reaction systems indicated that key intermediates made up of BNPP and Co (II) complexes are formed in the reaction process of BNPP catalytic hydrolysis. The mechanism of BNPP catalytic hydrolysis proposed is based on the analytic result of specific absorption spectra. Based on the mechanism proposed, a kinetic mathematical model for the calculation of the kinetic parameter of BNPP catalytic hydrolysis has been established. The acid effect of reaction system, structure effect of the complexes, effect of temperature and effect of micelles on the rate of BNPP hydrolysis catalyzed by the complexes have been discussed.     

苯并氮杂冠醚-15-冠-5 Schiff碱钴(Ⅱ)配合物在胶束中催化BNPP水解研究

在催化磷酸二酯水解的模拟酶模型中,配合物配体结构扮演了非常重要的角色[1-2]。由于冠醚环具有主客体识别功能,在酶学理论中把它作为模拟酶的第一代生物有机体。镶嵌有过渡金属离子的冠醚配合物对催化磷酸二酯水解具有很好的活性[3];Schiff碱过渡金属离子配合物对催化磷酸二酯水解也具有很好的活性[4]。因此,冠醚Schiff碱过渡金属离子配合物对催化磷酸二酯水解也应具有很好的活性,这已有所报道[5]。但冠醚结构和过渡金属离子相同而取代基不同的配合物作为模拟酶催化磷酸二酯水解还未见报道。本文按文献设计合成了三种冠醚结构相同而取代基…     

Studies on PNPP Hydrolysis Catalyzed by Schiff Base Cobalt（Ⅱ） Complexes

Two cobalt（Ⅱ） complexes of the Schiff base with morpholino or aza-crown ether pendants, CoL^1 and CoL^2, as mimic hydrolytic metalloenzyme, were used in catalytic hydrolysis of carboxylic ester （PNPP）. The analysis of specific absorption spectra of the hydrolytic reaction systems indicates that key intermediates, made up of PNPP and Co（Ⅱ） complexes, have been formed in reaction processes of the PNPP catalytic hydrolysis. The mechanism of PNPP catalytic hydrolysis has been proposed based on the analytic result of specific absorption spectrum. A kinetic mathematical model, applied to the calculation of the kinetic parameter of PNPP catalytic hydrolysis, has been established based on the mechanism proposed. The acid effect of buffer solution, structural effect of the complexes, and effect of temperature on the rate of PNPP hydrolysis catalyzed by the complexes have been also discussed.     

Studies on PNPP Hydrolysis Catalyzed by Divalent Metal Ion Macrocyclic Schiff Base Complexes in Micellar Solution

Two transitional metal ion macrocyclic Schiff base complexes, NiL and CuL were synthesized and characterized, and the metallomicelles made up of the nickel(II) and copper(II) complexes and surfactants(LSS, Brij35, CTAB), as mimic hydrolytic metalloenzyme, were used in catalytic hydrolysis of carboxylic ester (PNPP). The analysis of specific absorption spectrums of the hydrolytic reaction systems indicates that key intermediates, made up of PNPP and Ni(II) or Cu(II) complexes, have formed in the reaction processes of the PNPP catalytic hydrolysis. In this, based on the analytic result of specific absorption spectrum, the mechanism of PNPP catalytic hydrolysis has been proposed; a kinetic mathematical model, applied to the calculation of the kinetic parameter of PNPP catalytic hydrolysis has been established on the foundation of the mechanism proposed; the acid effect of reaction system, structure effect of the complexes, effect of temperature and effects of micelle on the rate of PNPP hydrolysis catalyzed by the complexes also have been discussed.     

Hydrolysis of Bis(4‐Nitrophenyl) Phosphate Catalyzed by Metallomicelle Made Up of the Crowned Schiff Base Complex as Synthetic Hydrolase

A crowned Schiff base ligand and its cobalt(II) and manganese(III) complexes were synthesized and characterized, and the metallomicelles made from the complexes and micelles (Brij35, LSS, CTAB) were investigated to catalyze the hydrolysis of bis(4‐nitrophenyl) phosphate (BNPP). A kinetic mathematical model for simulating enzyme catalyzing reaction was proposed and employed to analyze the mechanism of BNPP catalytic hydrolysis. Michanelis constant and the apparent active energy for the catalytic reaction were calculated. The kinetic studies showed that the metallomicelle made from the micelle and crowned Schiff base transitional metal complexes is an effective mimetic hydrolytic enzyme for BNPP catalytic hydrolysis.     

Study of the Intramolecular Reaction of an Activated Phosphate Ester in the Micelle System Containing Macrocyclic Complex

The intramolecular nucleophilic substitution of an activated phosphate diester, bis(p-nitrophenyl) phosphate (BNPP) as the nucleic acids substitute, was investigated. A macro-cyclic ligand and the corresponding Cu (II) and Ni (II) complexes were synthesized and characterized. The metallomicelles made up of macrocyclic divalent metal complex and micelle, as mimic hydrolytic metalloenzyme, was used in BNPP catalytic hydrolysis. The metallomicelles displayed higher catalytic activity although they do not attain the catalytic efficiency of enzymes. The analysis of specific absorption spectra showed that the course of the BNPP catalytic reaction was different from that of the BNPP spontaneous hydrolysis, and was an intramolecular nucleophilic substitution reaction. Based on the analytic result of the specific absorption spectrum, an intramolecular nucleophilic substitution mechanism of BNPP catalytic hydrolysis was proposed and a correlative kinetic mathematical model was established, and the corresponding thermodynamic and kinetic constant was calculated. The result of this study proved validity of the mechanism and mathematical model proposed in the article.     

Hydrolysis of BNPP Catalyzed by Metallomicelles Made of Pr(III) Complexes

A macrocyclic ligand was synthesized and characterized. The kinetics of hydrolysis of bis(p-nitrophenyl)phosphate (BNPP) in the catalytic system containing macrocyclic ligand and praseodymium(III) was investigated. The analysis of specific absorption spectrums of the hydrolytic reaction systems indicated that key intermediates made up of BNPP and praseodymium(III) complexes are formed in the reaction process of BNPP catalytic hydrolysis. In this, the mechanism of BNPP catalytic hydrolysis proposed is based on the analytic result of specific absorption spectrum, and the corresponding kinetic constants are calculated. The results showed that the praseodymium(III) complexes as hydrolase mimics exhibit good catalytic activity and similar catalytic character to natural enzyme.     

一种活性磷酸酯的分子内亲核取代反应动力学研究

合成和表征了大环过渡金属配合物NiL(L:高氯酸-5,7,7,12,14,14-六甲基-1,4,8,11-四氮杂环十四烷)。配合物NiL与表面活性剂组成的金属胶束作为模拟水解金属酶用于催化BNPP水解。提出了BNPP催化水解的机理;建立了用于计算动力学常数的动力学模型;计算了相关的动力学和热力学常数。结果表明,这种金属胶束表现出较高的催化活性;BNPP催化水解反应是分子内亲核取代反应;所提出的机理和建立的动力学模型是合理的。     

Studies on PNPP Hydrolysis Catalyzed by Schiff Base Cobalt（Ⅱ） Complexes Containing Benzoaza-15-crown-5

Three novel Schiff base cobalt（Ⅱ） complexes containing benzoaza-15-crown-5, CoL^1, CoL^2 and CoL^3 were synthesized and characterized, and these complexes were used in catalytic hydrolysis of carboxylic ester （PNPP, p-nitrophenyl picolinate） as mimic hydrolytic metalloenzyme. The analysis of specific absorption spectra of the hydrolytic reaction systems indicated that the catalytic hydrolysis involved the key intermediates formed by PNPP with cobalt（Ⅱ） complexes. The CoL^3 bearing the electron withdrawing group shows better catalytic activity due to its stabilization effect on active species MLS^-. The catalytic mechanism of PNPP hydrolysis was also proposed. The kinetic parameter of PNPP catalytic hydrolysis has been calculated and the activation energy for the catalytic hydrolysis is 43.69, 39.76 and 35.44 kJ·mol^-1, respectively.     

Studies on BNPP Cleavage by Schiff Base Complexes Containing Benzoaza‐15‐Crown‐5 in DHAB Micellar Solution

Two novel benzoaza‐crown Schiff base cobalt (II) and manganese (III) complexes were synthesized and characterized. The hydrolysis of bis(4‐nitrophenyl) phosphate (BNPP) catalyzed by the two complexes was studied in buffer solution containing dihexadecyldimethylammonium bromide (DHAB) at 25°±0.1°C and different pH values. The kinetic mathematical model of BNPP hydrolysis was proposed, and the effects of different reaction conditions on BNPP hydrolysis were discussed. The results indicate that the two complexes (MnLCl and CoL) can efficiently accelerate the catalytic cleavage of BNPP in DHAB micellar solution. The pseudo‐first‐order rate constants (k _obsd) of BNPP hydrolysis catalyzed by the metallomicelles of MnLCl/DHAB and CoL/DHAB are 2.32×10⁷ times and 1.45×10⁷ times higher than that of the BNPP spontaneous hydrolysis, respectively. Possible reasons for the huge rate accelerations include the lower critical micelle concentration (cmc) of DHAB and formation of metallomicelles made of complexes and DHAB. Furthermore, the BNPP cleavage catalyzed only by the two complexes was investigated in buffer solution. It was found that the hydrolytic rates of BNPP catalyzed only by the two complexes were about 1% of those catalyzed by MnLCl/DHAB and CoL/DHAB systems at 25°C, pH=7.00, and [BNPP]=2.0×10^?4 mol · dm^?3.     

冠醚化Schiff 碱配合物金属胶束催化BNPP水解动力学

研究了两种新的冠醚化Schiff 碱过渡金属配合物与表面活性剂Brij35(聚氧乙烯(23)十二烷基醚)形成的金属胶束对BNPP（对硝基苯酚磷酸二酯）的催化水解反应. 探讨了催化反应机理, 建立了一种金属胶束催化BNPP水解的动力学数学模型; 计算了模拟酶催化反应的相关参数和表观活化能. 结果表明, 此类金属胶束作为模拟水解金属酶对BNPP水解反应表现出良好的催化活性.     

Studies on the reaction kinetics and the mechanism of hydrolysis of bis(4-nitrophenyl) phosphate (BNPP) catalyzed by oxamido-bridged dinuclear copper(II) complexes in micellar solution

Oxamido-bridged dinuclear copper(II) complexes, used as symmetric two-center catalysts for the cleavage of BNPP, were synthesized and characterized. The reaction kinetics and the mechanism of hydrolysis of BNPP catalyzed by metallomicelles, made from complex (A) or (B) and a surfactant (LSS or CTAB), were investigated. A kinetic mathematical model for BNPP cleavage was also proposed. The results showed that the reaction rate for the catalytic hydrolysis of BNPP, compared with spontaneous hydrolysis of BNPP, increased by a factor of ca. 1 × 10⁶ due to the synergistic effect of two copper ions in the complex and the local concentration effect of the micelle. The study indicates that the metallomicelle-containing oxamido-bridged dinuclear copper(II) complex may be a potential catalyst for the hydrolysis of BNPP.     

Studies on the reaction kinetics and the mechanism of hydrolysis of bis(4-nitrophenyl)phosphate (BNPP) by hydroxamic acid complexes containing benzo-15-crown-5

A hydroxamic acid (HL) containing benzo-15-crown-5 and their copper(II), zinc(II), cobalt(II) and manganese(II) complexes have been synthesized and studied as catalysts for the cleavage of bis(4-nitrophenyl)phosphate (BNPP). The catalytic properties of these complexes and the kinetics and mechanism of BNPP hydrolysis have been investigated. The kinetic mathematical model of BNPP cleavage catalyzed by these complexes has been proposed. The effects of reaction temperature and metal ion in the complexes on the rate of BNPP catalytic hydrolysis have been discussed. The results show that the hydroxamic acid complexes containing benzo-15-crown-5 exhibit high activity in the BNPP catalyzed hydrolysis; the pseudo-first-order-rate constants of BNPP hydrolysis catalyzed by the complexes increase along with the increases of pH of the buffer solution from 7.50 to 9.50; the activity of different metal ions decreases in the order: Co²⁺ > Cu²⁺ > Zn²⁺ > Mn²⁺; the pseudo-first-order-rate constants of BNPP hydrolysis catalyzed by the complexes is 2.24 × 10⁵ ~ 3.24 × 10⁵ times as large as that of spontaneous hydrolysis of BNPP.     

双Schiff碱过渡金属配合物在胶束溶液中催化BNPP水解的研究

双Schiff碱过渡金属配合物和胶束形成的金属胶束作为模拟磷酸二酯水解酶用于催化BNPP水解，探讨了催化作用机理；提出了一种金属胶束催化BNPP水解的动力学数学模型。研究表明，本文所用的金属胶束在适当酸度、温度、介质的条件下对催化BNPP水解具有较高的活性。     

阳离子表面活性剂金属胶束作为模拟磷酸酯水解酶的研究

在模拟水解酶的研究中,模拟模型中配体的功能已经受到普遍重视,冠醚是外腔疏水而内腔亲水的物质,因此已被用作模拟水解酶模型中的配体。这些模型可以分为两类,一是金属离子镶嵌在冠醚环中所形成的穴状配合物模型,二是以冠醚基作为支链的冠醚化Schiff碱配合物。穴状配合物模型作为模拟水解酶用于催化磷酸酯的研究已经取得了一定的进展。     

含肟基的钴和铜双核金属配合物催化磷酸二酯水解

本文合成了双核铜（II）和钴（II）配合物,并用动力学方法研究了它们对双-（对硝基苯基）磷酸二酯（BNPP）水解的催化活性。实验结果表明,单去质子化的肟基可以作为反应过程中的分子内亲核剂。双核铜（II）配合物比与其具有相似结构的单核配合物催化底物水解的活性高很多的事实表明,在双核配合物作催化剂的体系中很可能包含两个金属中心的双路易斯酸催化的机理。     

Studies on Phenol Oxidation with H2O2 Catalyzed by Schiff Base Cobalt(II) Complexes in Micellar Solution

The two Schiff base cobalt(II) complexes, CoL¹ and CoL², were synthesized and characterized. The metallomicelle made up of the cobalt(II) complexes and surfactants (CTAB, LSS and Brij35), as mimic peroxidase metalloenzyme, were used in the catalytic oxidation of phenol by H₂O₂. The mechanism and a kinetic mathematic model of the phenol catalytic oxidation were studied. The acid effect of reaction system, structural effect of the complexes, and effect of temperature on the rate of the phenol oxidation catalyzed by the mimetic peroxidases have been discussed. The results showed that the schiff base cobalt(II) complexes and their metallomicelles as peroxidase mimics exhibit good catalytic activity and similar catalytic character to natural enzyme.     

Phosphate Diester Cleavage Promoted by the Metallomicelles of Ce(III) Complexes of Aza-Crown Ether with Different Numbers of Nitrogen Atoms

The design of artificial hydrolase has attracted extensive attention due to their scientific significance and potential application in the field of gene medicine and molecular biology. This work reports the catalytic activation of two aza-crown ether Ce(III) complexes and their metallomicelles as artificial hydrolase in bis(4-nitrophenyl) phosphate ester (BNPP) hydrolysis. The chemical composition of two complexes was determined by the fluorescence spectra and the mole ratio method for electronic absorption spectra. The bonding effect of BNPP and solubilizing effect of the complexes were proved by a method of fluorescence spectroscopy. The catalytic activity of different catalytic systems in BNPP hydrolysis was measured with UV-vis spectrophotometric method. These catalytic systems showed high catalytic activity for promoting BNPP hydrolysis at the almost physiological conditions. BNPP hydrolysis rate in these catalytic system is about 10⁷- to 10⁹-fold faster than that of the BNPP spontaneous hydrolysis in aqueous solution at the same conditions. The metallomicelle systems exhibited higher catalytic activity compared with the complex solution systems in BNPP hydrolysis, and hexadecyltrimethyl ammonium bromide micelle provides a useful catalytic environment for reaction. The acid effect of the catalytic system is ascribed to the formation of metal-bound hydroxide serving as a better kind of nucleophile.     

Metallomicellar catalysis: accelerated hydrolysis of BNPP by copper(II), zinc(II), and nickel(II) complexes of long alkanol-imidazole in CTAB micellar solution

Two alkanol-imidazole ligands have been synthesized. Metal (Cu(II), Zn(II), Ni(II)) complexes of these ligands have been investigated as catalysts for the hydrolysis of bis(p-nitrophenyl) phosphate (BNPP) in the buffered CTAB co-micellar solution at 30 degrees C and various pH values, respectively. The ternary complex kinetic model for metallomicellar catalysis was employed to analyze the results, to obtain the kinetic and thermodynamic parameters. The effect of the structure of the ligands and the microenvironment of the reaction on the hydrolytic reaction of BNPP has been discussed in detail. The results indicate that the hydrophobic interaction between the substrate and the metallomicellar catalyst and the micellar microenvironment are important factors.