Catalytic Kinetics of the Schiff Base Metal Complexes Bearing Side Chain of Cyclic morpholine in Carboxylic Ester Hydrolysis

It has been reported that two Schiff base transition metal complexes bearing the side chain of the morpholine ring were synthesized and characterized, and two complexes with the same base agent but different metal ions were used as a simulant hydrolase in the catalytic hydrolysis of p-nitrophenyl picolinate in this paper. The mechanism of PNPP catalytic hydrolysis is proposed and supported by the results of the spectral analysis and the kinetic calculation. A kinetic mathematical model, applied to the calculation of the kinetic and thermodynamics parameters of PNPP catalytic hydrolysis, has been established on the foundation of the mechanism proposed. The result of the study shows that the two complexes have a good catalytic activity in PNPP catalytic hydrolysis, and the rate of the PNPP catalytic hydrolysis was increased with the increase of the pH values in the buffer solution and affected by the polarization effect of metal ion of the complexes.     

Synthesis, mechanism and NMR spectra of lanthanide complexes with a novel unsymmetrical Schiff base

Owing to its two unsymmetrical-NH_2 groups sited on different terminals, 2, 6-diaminocaproic acid (lysine) was used as a reactant for synthesizing a novel unsymmetrical Schiff base with salicylaldehyde on one side and ovanillin on the other for the first time. It is a new way to synthesize such a special unsymmetrical Schiff base. It is named "hetero bis-Schiff base" for distinguishing it from others. The synthesis method, formation mechanism as well as twelve new lanthanide complexes with the above ligand are reported and discussed herein. They were characterized by elementary analysis, molar conductivity, IR-spectra and especially by ~1H and ~(13)C NMR spectra. The results obtained may provide a new promising method for synthesizing similar unsymmetrical Schiff bases and their complexes.     

Preliminary Screening of Non-platinum Complexes of Schiff Bases as Antitumour Agents Using Fluorimetry

Based on the consistency of the in vivo and in vitro interactions of drugs with DNA, a fluorimetric method has been developed as a new in vitro method for preliminary screening of antitumour agents. This method was tested using Schiff bases synthesized from salicylaldehyde with 1-alanine, 1-asparagine and 1-histidine, and complexes of these Schiff bases with Cu(Ⅱ), Zn(Ⅱ), Ni(Ⅱ) and Sn(Ⅳ) as potential antitumour agents.The study of the interaction of the complexes with DNA by a fluorescence probe ethidium bromide (EthBr)-DNA system indicated the parallelism between the binding constants and antineoplastic ratios. The relationship between structure and antitumonr activity was investigated.     

Rare earth complexes with noncyclic polyether-methionine Schiff base

A novel Schiff base (TAMET) was synthesized by the condensation of tetraglycol aldehyde with methionine and a mild oxidant CrO3· (C5H5N)2 was selected for the reaction. Seven new rare earth complexes with this Schiff base have been synthesized and characterized by elemental analysis, TG-DTA, molar conductivity, magnetic susceptibility and IR, especially 1H NMR spectra. Information was obtained from reflectance spectra and the coordination of sulfur atom to rare earths was discussed. The experimental results show that thesecompounds have some biological activity and could dispose of O2.     

Computational Investigation on the Ethylene-induced Esterase from Citrus Sinensis

In order to understand the interaction between ethylene-induced esterase(EIE, EC 3.1.1.) from Citrus sinensis and α-naphthyl acetate, a 3D model of EIE was generated based on the crystal structure of the tobacco salicylic acid binding protein 2(SABP2). With the aid of the molecular mechanics and molecular dynamics methods, the final refined model was obtained and its reliability was further assessed. In this study, the docking results show that the main-chain amide of residue His85 and residue Val18 can form hydrogen bonds to the carbonyl oxygen group of α-naphthyl acetate. MM-PBSA method was applied to calculating the binding free energy between EIE mutants and α-naphthyl acetate. Our calculated binding free energy of each of the two mutant complexes is increased compared with that of the one of the wild type, which is unfavorable to the reaction. It is well consistent with the experimental data. The above results clearly indicate that His85 and Val18 in EIE function as the oxyanion role and take part in the catalytic reaction. The new structural insights obtained from this computational study are expected to stimulate further biochemical studies on the structures and mechanisms of EIE and other members of the plant α/β hydrolases.     

Synthesis and Crystal Structure of Lanthanide Schiff Base Complex [2-OC6H4CHN（2,6-i-Pr2C6H3）]2ErCl（THF）

1 INTRODUCTION The Schiff base ligands have been used to provide a stereochemically rigid ligand framework in homogenous precatalysts of some metals, such as salen Cr catalysts in asymmetric ring-opening re- action of epoxide[1] and salen Al in ring-opening polymerization of lactide and related cyclic esters[2]. Recently, it was reported that the bidentate Schiff base complexes of early and late transition metals can be served as promising alternatives to metal- locene catalysts for th…     

手性铜(Ⅱ)-席夫碱配合物催化苯乙烯不对称环丙烷化反应

Twelve chiral copper(Ⅱ) Schiff base complexes, derived from (R) (+) 2 amino 1,1 diaryl 1 propanol with substituted salicylaldehydes, were examined as a catalyst for asymmetric cyclopropanation of styrene with ethyl diazoacetate. It was found that the substituents at 3 and 5 positions of salicylaldehyde in the ligands had great effects on catalytic activity and enantioselectivity of the catalyst. The complex with strong electron withdrawing group (NO 2) at 5 position and the smallest stereo hinder (H) at 3 position of salicylaldehyde showed highly catalytic activity and enantioselectivity, up to ee =87 4% for trans and ee =82 8% for cis isomers respectively, and the ratio 39/61 of cis to trans isomers was obtained at 40 ℃ with 1,2 dichloroethane as solvent.     

Theoretical Studies on the Mechanism of Photocycloaddition Reaction Between 6 Azauracil and Acetone

The mechanism of photocycloaddition reaction between 6-azauracll and acetone was studied by using semiemptrical SCFMO AMI method. It was found that this reaction is not a concerted one. The calculated results are as follows:(1) A T1 state exciplex is on the T1 state energy surface; (2) T exciplex as a reactant will proceed along the energy surface of T1 state to form a diradical intermediate. The energy barrier of this reaction step is 63. 6 kJ/mol; (3) The T1 state diradical intermediate happens to be close in energy to the ground state intermediate with a similar geometry. Such a situation turns out to be very favorable for an intersystem crossing (jump from the T, state to the ground state) ; (4) The final product will be formed from the ground S0 state intermediate via an energy barrier 88. 2 kJ/mol.     

Metal complexes of anthranilic acid derivatives: A new class of noncompetitive α-glucosidase inhibitors

Metal complexes of anthranilic acid derivatives that constitute a novel class of non-sugar-type aglucosidase inhibitors were synthesized and assessed in vitro for inhibitory activity. All of the Ag(I)complexes(9–16) inhibited a-glucosidase at the nanomolar scale, while 3,5-dichloroanthranilic acid silver(I)(9) was the most potent(IC_(50)= 3.21 nmol/L). Analysis of the kinetics of enzyme inhibition indicated that the mechanism of the newly prepared silver complexes was noncompetitive. The structure-activity relationships were also analyzed, and they are discussed in this report.     

Preparation and Catalytic Properties of Polymer-Bound Schiff Base Ternary Complexes

The polymer-bound Schiff base ternary manganese complexes [PS-SalPhe-Mn-L (L = Phen, Bipy and 8HQ)] have been prepared from the polymer-bound Schiff base ligand, a manganese salt and the second ligand, such as 1,10-phenanthroline (phen), 2,2‘-bipyridyl (bipy) and 8-quinolinol (8HQ). The polymer-bound Schiff base ternary manganese complexes were characterized by means of infrared spectrometry and ICPAES. The catalytic activities of the complexes have been studied in the aerobic epoxidation of long-chain linear aliphatic olefins. It is shown that 1-octene or 1-decene can be directly oxidized by molecular oxygen when catalyzed by PS-SalPhe-Mn-L(L=Phen, Bipy and 8HQ), and 1,2-epoxy alkane can be afforded in these reactions.     

Synthesis and catalytic activity of Ln (III) complexes with an unsymmetrical Schiff base including multi“非汉字符号” C=N—groups

Complexes with the unsymmetrical Schiff base can be used effectively as the stimulated metal protein and catalyst with higher activity. In order to obtain an unsymmetrical bis-Schiff base, Elder[1] suggested that the nickel bis-Schiff base complex was prepared firstly, then the corre-sponding unsymmetrical bis-Schiff base was synthesized by stripping the ligand from this com-plex with dimethylglyoxime. The resulting product with an additional —NH2 group may be con-densed with another aldehy…     

Enolic Schiff Base Zinc Amide Complexes: Highly Active Catalysts for Ring-Opening Polymerization of Lactide and ε-Caprolactone

A series of zinc silylamido complexes based upon NNO tridentate enolic Schiff base framework have been synthesized and characterized. These complexes were tested for the ring opening polymerization of lactide and ε-caprolactone, exhibiting notably high activity at ambient temperature. The influence of imine bridge length and substituents of diketone over the course of polymerization was investigated in details. Remarkably, 4 a was confirmed to be a rare example of exceedingly active and robust zinc catalysts, achieving major transformation of lactide under extremely low loading(0.025 mol%) within 18 min. The influence of various monomers as well as the polymerization mechanism have also been discussed.     

Synthesis and catalytic activity of novel heteronuclear Ln(Ⅲ)-Cu(Ⅱ) complexes with noncyclic polyether-amino acid Schiff base

A series of novel heteronuclear Ln(Ⅲ)-Cu(Ⅱ) complexes with noncyclic polyether-amino acid Schiff base were synthesized. The general formula is [LnCu_2(H_2TALY)(NO_3)_5](NO_3)_2' nH_2O(Ln=La, Nd, Sm, Gd, n= 4; Ln=Yb, Y, n=3), where H_2TALY = tetraglycol aldehyde bis-lysine Schiff base. It is the first time to report the synthetic method for this new Cu(Ⅱ) complexes and Ln(Ⅲ)-Cu(Ⅱ) heteronuclear complexes. The complexes were characterized by elemental analysis, IR spectra, TG-DTA, magnetic susceptibility, and especially by a 500 MHz NMR spectrometer for 2D-COSY NMR. Coordination mechanism and structures of complexes have been suggested as well. Of particular interest is the potential that the novel complexes obtained may be used as a catalyst, which prompted us to investigate them. It shows 100% conversion with the viscosity-average molecular weight 120 000 for the polymerization of methyl methacrylate (MMA) without addition of any cocatalyst. Furthermore, the complexes with such aliphatic Schiff bas     

Dioxygen Affinity and Catalytic Performance of Bis-(furaldehyde) Schiff Bases Co(II) Complexes in Cyclohexene Oxidation

As mimetic oxygen carrier or oxidation catalyst, Schiff base cobalt complexes such as Co (II) salen have been widely studied1-4. However their high-price greatly limited their application. The synthesis of cheap furaldehyde Schiff bases and their complexes with Co (II), as well as the dioxygen affinity and biomimetic catalytic oxidation performance of these complexes are worth trying to study. In this paper, the saturated dioxygen uptake of cobalt complexes with different bis-(furaldehyd…     

Tuning the base properties of Mg–Al hydrotalcite catalysts using their memory effect

Herein,the relationship between the structure and base properties of Mg–Al hydrotalcite catalysts was comprehensively investigated in relation to heat treatment and rehydration processes,which are well known as memory effects of hydrotalcite.The structure of Mg–Al hydrotalcites changed from layered double hydroxide(LDH)to mixed metal oxide and subsequently to a spinel structure during heat treatment,and it was returned from mixed metal oxide to a LDH structure by rehydration.Based on various characterizations,we successfully proposed a detailed mechanism of memory effect.We also confirmed that the Mg–Al hydrotalcites had weak or strong base sites and that their base properties could be systematically tuned by heat treatment and rehydration.The prepared Mg–Al hydrotalcites were applied to a model reaction,isomerization of glucose to fructose,as base catalysts.Among the catalysts tested,the rehydrated Mg–Al hydrotalcite efficiently produced fructose due to its appropriate base and structure properties.We finally concluded that the base sites of Mg–Al hydrotalcites can be designed as desired by heat treatment and rehydration.Moreover,through systematic design of the base sites of Mg–Al hydrotalcites,these can be promising catalysts for various heterogeneous reactions over base catalysts,giving excellent catalytic performances.     

Extraction of cobalt(Ⅱ) from aqueous solution by N,N'-carbonyl difatty amides

The development of economic and environmentally friendly extractants to recover cobalt metal is required due to the increasing demand for this metal.In this study,solvent extraction of Co(Ⅱ) from aqueous solution using a mixture of N,N’-carbonyl difatty amides(CDFAs) synthesised from palm oil as the extractant was carried out.The effects of various parameters such as acid,contact time,extractant concentration,metal ion concentration and stripping agent and the separation of Co(Ⅱ) from other metal ions such as Fe(Ⅱ),Ni(Ⅱ),Zn(Ⅲ) and Cd(Ⅱ) were investigated.It was found that the extraction of Co(Ⅱ) into the organic phase involved the formation of 1:1 complexes.Co(Ⅱ) was successfully separated from commonly associated metal ions such as Fe(Ⅱ),Ni(Ⅱ),Zn(Ⅲ) and Cd(Ⅱ).Co(Ⅱ) stripping from the loaded organic phase was studied in aqueous solution.These results are useful to recover Co(Ⅱ) from aqueous solution utilising(CDFAs) as an extractant.     

STUDIES ON THE PROPERTIES OF SCHIFF BASE TYPE ARYLMERCURY COMPOUNDS Ⅲ TRANSMETALLATION REACTION OF SCHIFF BASE TYPE ARYLMERCURY COMPOUNDS WITH METALLIC TIN

The transmetallation reaction of 4 Schiff base type arylmercury compoundswith metallic tin has been carried out in refluxing xylene.It was found that thereaction proceeds in the same manner as that of chloro[2-(phenylazo)phenyl]mercury(Ⅱ)to give dichlorobisaryltin(Ⅳ).The ~1H NMR spectra of the products provide evidence forthe presence of N→Sn intramolecular coordination.The formation ofdichlorobisaryltin(Ⅳ)as a unique product probably arises from the N→Sn intramolecularcoordination which results in the increasing of the stability of the molecule.     

Study on the recovery of hydrogen from refinery (hydrogen + methane) gas mixtures using hydrate technology

A novel technique for separating hydrogen from (H2 CH4) gas mixtures through hydrate formation/dissociation was proposed. In this work, a systematic experimental study was performed on the separation of hydrogen from (H2 CH4) feed mixtures with various hydrogen contents (mole fraction x = 40%-90%). The experimental results showed that the hydrogen content could be enriched to as high as ~94% for various feed mixtures using the proposed hydrate technology under a temperature slightly above 0℃ and a pressure below 5.0 MPa. With the addition of a small amount of suitable additives, the rate of hydrate formation could be increased significantly. Anti-agglomeration was used to disperse hydrate particles into the condensate phase. Instead of preventing hydrate growth (as in the kinetic inhibitor tests), hydrates were allowed to form, but only as small dispersed particles. Anti-agglomeration could keep hydrate particles suspended in a range of condensate types at 1℃ and 5 MPa in the water-in-oil emulsion.     

Synthesis and Structure of anti-Configuration Complex [Cu(tssb)_2]·2[(H_3O)Cl]·4H_2O

1 INTRODUCTION The complexes of amino acid Schiff base have attracted considerable attention because of their bio- activities[1, 2]. Taurine is a special amino acid in be- ings, and recently the complexes of taurine conden- sation salicylaldehyde Schiff …     

Synthesis of dimethyl adipate from cyclopentanone and dimethyl carbonate over solid base catalysts

A facile route for the synthesis of dimethyl adipate (DAP) from cyclopentanone and dimethyl carbonate (DMC) in the presence of solid base catalysts has been developed.It was found that the intermediate carbomethoxycyclopentanone (CMCP) was produced from cyclopentanone with DMC in the first step,and then CMCP was further converted to DAP by reacting with a methoxide group.The role of the basic catalysts can be mainly ascribed to the activation of cyclopentanone via the abstraction of a proton in the α-position by base sites,and solid bases with moderate strength,such as MgO,favor the formation of DAP.