COORDINATION POLYMERIZATION OF BENZOTRIAZOLE ON THE SURFACE OF METALLIC COPPER

The coordination polymerization of benzotriazole with metallic copper has been investigated by infrared and X-ray photoelectron spectroscopies. We found that benzotriazole could react with copper (0) under mild conditions to form bis (benzotriazolato) copper (Ⅱ) and benzotriazolato copper (Ⅰ)which covered the surface of copper metal in the shape of polymeric materials. Since benzotriazole is of great interest as a ligand in that its presence in many biological system with metal ions, and is considered as a corrosion inhibitor, this work will be in favour of the study of protective corrosion.     

Microwave-assisted Polymerization of D,L-Lactide with Stannous Octanoate as Catalyst

Poly (lactic acid) (PLA) is an important member of the polyesters which are used as biomedical materials in bioresorbable suture, implantates and drug controlled release systems1. PLA is prepared by two routs2: ring-opening polymerization of dimeric cyclic lactide or direct polycondensation of lactic acid. The ring-opening polymerization has attracted much more scientific and industrial interests than the later one, but both methods need long time for the polymerization reactions to be compl…     

Synthesis and Structure of the Copper(Ⅰ) Complex [Cu(PPh3)2(BH4)]

Mononuclear copper( Ⅰ ) complex [Cu(PPh3)2(BH4)] has been synthesized by ligand replacement reaction in methanol and characterized by elemental analyses, molecular weight determination, IR spectra and X-ray single crystal analysis,its conductivity has also been measured. The crystal is monoclinic, space group C2/c, a =24.776(4), b=9.173(7), c=15.564(2)A; β=116.10(1)°, V=3176.73 A3, Z =4, F(000)=1256, μ(MoKα)=8.11 cm-1, Dc=1. 26 g/cm3, M=602.79, R=0. 039, Rw= 0. 050. The results show that PPh3 coordinates as monodentate ligand to the Cu ( Ⅰ ) atoms, and BH4 behaves as a bidentate ligand in the prepared complex.The central copper atom belongs to tetrahedron coordination geometry.     

Stereoselective ring-opening polymerization of rac-lactide by bulky chiral and achiral N-heterocyclic carbenes

Despite the extraordinary success has been achieved in metal catalyst-promoted stereoselective ring-opening polymerization(ROP) of rac-lactide(rac-LA), well-controlled stereoselective rac-LA ROP by organic catalyst still remains a scientific challenge. Here we report our investigations into organocatalytic stereoselective ROP of rac-LA by utilizing novel bulky chiral and achiral N-heterocyclic carbenes(NHC), 1,3-bis-(1′-naphthylethyl)imidazolin-2-ylidene. The effect of polymerization conditions(e.g. solvent, temperature, alcohol initiator) on ROP behavior by these bulky NHCs has been fully studied, leading to the formation of isotactic-rich stereoblock polylactide(P_i = 0.81) under optimized conditions with high activity(Conv. = 98% in 30 min) and narrow molecular weight dispersity(? = 1.05).     

SYNTHESIS AND CHARACTERIZATION OF Co(Ⅱ) COMPLEX OF 14-MEMBERED HEXAAZA MACROCYCLIC LIGAND WITH AXIALLY COORDINATED BROMIDES

The macrocyclic ligand complex, [Co(C_(18)H_(18)N_6) Br_2]·1/2H_2O, has been synthesized by the template condensation of 2, 6-diacetylpyridine with hydrazine in the presence of cobalt (Ⅱ) dibromide and characterized by IR, ESR, electronic spectra and magnetic properties. Based on these data, the complex is proposed to be an approximate elongated octahedron with low spin state. The absorption bands of d-d transition are assigned, and the values of various ligand field parameters have been evaluated and are discussed in terms of their chemical utilities. ESR study on the complex has been carried out. The values of g(?)and g(?) have been determined. From ligand field parameter values and gvalues, μ_(eff)=2.06 BM has been obtained, which is consistent with the experimental value(2.04BM).     

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…     

Hybrid Copolymerization via the Combination of Proton Transfer and Ring-opening Polymerization

Phosphazene base,t-BuP2,was employed to catalyze the proton transfer polymerization(PTP)of 2-hydroxyethyl acrylate(HEA),and PTP was further combined with ring-opening polymerization(ROP)to exploit a new type of hybrid copolymerization.The studies on homopolymerization showed that t-BuP2 was a particularly efficient catalyst for the polymerization of HEA at room temperature,giving an excellent monomer conversion.Throughout the polymerization,transesterification reactions were unavoidable,which increased the randomness in the structures of the resulting polymers.The studies on copolymerization showed that t-BuP2 could simultaneously catalyze the hybrid copolymerization via the combination of PTP and ROP at 25°C.During copolymerization,HEA not only provided hydroxyl groups to initiate the ROP ofε-caprolactone(CL)but also participated in the polymerization as a monomer for PTP.The copolymer composition was approximately equal to the feed ratio,demonstrating the possibility to adjust the polymeric structure by simply changing the monomer feed ratio.This copolymerization reaction provides a simple method for synthesizing degradable functional copolymers from commercially available materials.Hence,it is important not only in polymer chemistry but also in environmental and biomedical engineering.     

KINETICS OF POLYMERIZATION OF ACRYLONITRILE INITIATED BY VANADIUM(V)-THIOUREA REDOX SYSTEM

The kinetics of polymerization of acrylonitrile (AN) initiated by quinquevalent vanadium (V~(5+))-thiourea (TU) redox system has been investigated in aqueous nitric acid in the temperature range from 30 to 50℃. The polymerization rate (R_p) can be expressed as follows: In the copolymerization of acryionitrile with methyl acrylate (MA), the reactivity ratios were found to be 1.0 and 1.1, respectively. The experimental observations suggest that the initiating species is probably a complex consisting of a central ion of Lewis acid-VO_2~+ and the ligands of Lewis bases-acrylonitrile, thiourea, and nitrate anions, while the initiating system in lower concentration, the polymerization of acrylonitrile does not occur if the thiourea is acidified prior to its reaction with quinquevalent vanadium. This indicates that the primary radicals (or the monomeric radicals in the present article) are produced by associated thiourea rather than isothlourea.     

Synthesis,Crystal Structure and Copper Complex of 1,3-Alternate p-tert-Butylthiacalix[4]arene 2-picolyl Schiff Base

A p-tert-butylthiacalix[4]arene-based polydentated ligand with four Schiff base units on 1,3-alternate position at lower rim has been prepared in three steps,which coordinated to copper ion to form a novel dicopper complex.The structures of the polydentated thiacalixarene ligand and copper complex were fully characterized by spectroscopy and X-ray single crystal diffraction method.     

N-乙基-1，10-菲罗啉-2-甲胺镍(Ⅱ)配合物的合成、晶体结构及性质研究(英)

A novel ligand N-ethyl-1,10-phenanthroline-2-methanamine and its Ni(Ⅱ) complex have been synthesized. The crystal structure of the complex has been determined by X-ray diffraction method. The Ni(Ⅱ) is five-coordinated by three nitrogen atoms from the ligand and two Cl^- anions in a distorted trigonal bipyramidal environment: the N(2), Cl(1) and Cl(2) in equatorial plane; the N(1) and N(3) in axial positions. The UV-spectra and IR-spectra of the ligand and its Ni(Ⅱ) complex were recorded and discussed. The thermodynamic properties of the ligand with various bivalent metals were studied by potentiometric titrations and the order of the stability constants is in agreement with the Irving-Williams order in coordination chemistry. CCDC: 221750.     

Binuclear Aluminum Complexes Supported by Linked Bis(β-diketiminate) Ligands for Ring-Opening Polymerization of Cyclic Esters

Binuclear aluminum alkyl complexes 2a–4g supported by linked bis(β-diketiminate) ligands were synthesized via the reaction of AlEt_3 or AlMe_3 and the corresponding proligand in a 2:1 molar ratio with moderate yields. The isolated complexes were well-characterized by ~1H-NMR, ~(13)C-NMR and elemental analysis. The binuclear nature of aluminum complex 2b was further confirmed by an X-ray diffraction study. All complexes 2a–4g could efficiently initiate the ring-opening polymerization(ROP) of ε-caprolactone in toluene. The substituents at the aromatic rings and the linker unit in the auxiliary ligands exerted significant influence on the catalytic behavior of the investigated aluminum complexes. Complex 4g(R~1 = R~2 = Cl) containing propylenyl bridging unit exhibited the highest catalytic activity among these complexes, which might be attributed to the increased electrophilicity of the metal center as well as more opened coordination sphere. The molecular weights of obtained poly(ε-caprolactone)s deviating considerably from the theoretical values indicated that the ROP of ε-caprolactone by complexes 2a–4g was not well-controlled, which was also judged from the broad molecular weight distributions(MWD = 1.47-2.47) of produced poly(ε-caprolactone)s. These complexes proved to be inactive toward the polymerization of rac-lactide alone. In the presence of alcohol the polymerization occurred, which was actually initiated by the decomposition species of the aluminum complex upon the treatment with isopropanol.     

SINGLE LANTHANUM TRIS(N-PHENYLETHYL-3,5-DI-t-BUTYLSALICYLALDIMINATO)S INITIATOR FOR RING-OPENING POLYMERIZATION OF 1,4-DIOXAN-2-ONE IN BULK

A rare earth Schiff base complex:lanthanum tris(N-phenylethyl-3,5-di-t-butylsalicylaldiminato)s [La(OPEBS)_3] was successfully applied as single component initiator for the ring-opening polymerization of 1,4-dioxan-2-one (PDO) in bulk.The influence of reaction conditions,such as polymerization temperature,the molar ratio of the monomer to initiator (M/I) on the monomer conversion and molecular weight of the polymer has been investigated.Poly(1,4-dioxan-2-one) with a viscosity-average molecular weight (My...     

Synthesis,Crystal Structure and Biological Properties of One Zinc(Ⅱ) Complex Based on 4-Acyl Pyrazolone Derivative

[Zn(L)(CH3OH)3](H2L = N-(1-phenyl-3-methyl-4-propenylidene-5-pyrazolone)-salicylidene hydrazide) has been synthesized by the reaction of zinc nitrate and ligand H2 L. The complex crystallizes in orthorhombic system, space group Pbca with a = 5.888(15), b = 14.564(14), c = 22.20(2) , V = 5137(8) 3, Z = 8 and F(000) = 2184. The ligand serves as a negative bivalent tridentate chelating agent to coordinate with the central zinc(II) atom. DNA-binding was studied by UV-Vis spectral analysis and ethidium bromide(EB) displacement experiments. The results showed that the DNA-binding constant of the complex is 5.1×104 M–1. Antitumor activity of [Zn(L)(CH3OH)3] and the ligand have been investigated by MTT assay, which indicated that the complex has better cytotoxicity to Eca-109 and He La than free ligand.     

PHOTOSENSITIVITY OF Ce (Ⅳ) INITIATED METHYL ACRYLATE POLYMERIZATION

The influences of UV light irradiation (313 nm) and diffused daylight on the polymerization of methyl acrylate initiated by the ceric ammonium nitrate without any reducing agent have been studied both in aqueous nitric acid and in pure water. The rate of polymerization was found to be accelerated and the overall activation energy and the induction time were found to be decreased sharply by the UV light irradiation. Under UV light, the rate of polymerization is 8 times as high as the rate in dark. The rate of polymerization was found to attain a maximum with the increase of nitric acid concentration and the rate of polymerization became less sensitive to UV light in the presence of nitric acid whereas the induction period reduced outstandingly. Based on the experimental results, the mechanism is proposed.     

稀土硫化物：e–己内酯开环聚合新催化剂

The ring-opening polymerization （ROP） of ε-caprolactone （ε-CL） using lanthanide thiolate complexes [（CH3CsH4）2Sm（μ-SPh）（THF）]2 （1） and Sm（SPh）3（HMPA）3 （2） as initiators has been investigated for the first time. Both of 1 and 2 were found to be highly efficient initiators for the ROP of ε-CL. The poly（ε-caprolactone） （PCL） with molecular weight Mn up to 1.97 ×10^5 and relatively narrow molecular weight distributions （1.20〈MW/Mn〈 2.00） have been obtained in high yield in the temperature range of 35-65℃. According to the polymer yield, 2 showed much higher activity than 1. However, the number-average molecular weight of PCL obtained with 2 was much lower than with 1. The possible polymerization mechanism of the ε-CL polymerization has been proposed based on the results of the end group analysis of the ε-CL oligomer.     

Synthesis of Well-defined Poly(tetrahydrofuran)-b-Poly(α-amino acid)s via Cationic Ring-opening Polymerization(ROP) of Tetrahydrofuran and Nucleophilic ROP of N-thiocarboxyanhydrides

The synthesis of block copolymers of poly(tetrahydrofuran)-b-poly(α-amino acid)(PTHF-b-PAA) is challenging since it is difficult to combine the two blocks produced via different/conflicting ring-opening polymerization(ROP) mechanisms. In this contribution, the cationic ROP of THF is catalyzed by rare-earth triflate [RE(OTf)_3] and terminated by 2-(t-butyloxycarbonyl-amino) ethanol(BAE). After the deprotection of tbutyloxycarbonyl(Boc) group, the chain end of PTHF is quantitatively changed to amino group which thereafter initiates the nucleophilic ROP ofα-amino acid N-thiocarboxyanhydrides(NTAs). Both polymerizations are well controlled, generating PTHF and PAA segments with designable molecular weights(MWs). PTHF-b-polylysine(PTHF-b-PLys) and PTHF-b-polysarcosine(PTHF-b-PSar) are obtained with MWs between 8.6 and28.7 kg/mol. The above amphiphilic diblock copolymers form micelles in water. PTHF_(40)-b-PSar_(32) acts as a surfactant to stabilize oil-in-water emulsions. Both segments of PTHF-b-PAA are biocompatible and promising in the biomedical application.     

STUDY OF CARBONYLATION OF METHANOL TO ACETIC ACID AND ACETIC ANHYDRIDE OVER A BIDENTATE POLYMER BOUND CIS-DICARBONYLRHODIUM COMPLEX AS CATALYST

Copolymer of 2-vinylpyridine and vinylacetate coordinated with dicarbonylrhodiumused as a catalyst for carbonylation of methanol to acetic acid and anhydride has beenstudied. The structural characteristics of the copolymer ligand and complex, and the in-fluences of the reaction conditions on the carbonylation catalyzed by this polymer complexhave been investigated. In comparison with small molecule catalyst of Rh complex, thebidentate copolymer coordinated complex has better thermal stability. The reactionmechanism of the carbonylation reaction is also illustrated.     

Synthesis and Liquid Crystal Behaviors of 2,4-Dioxo-3-pentyl 4-decyloxy Cinnamate Rhodium （I） Complexes

The title complexes have been synthesized by the reaction of [RhCI(CO)2]2 or [RhCI(COD)]2 (COD = 1,5-cyclooctadiene)with the organic ligand 2,4-dioxo-3-pentyl 4-decyloxy cinnamate 2. The complex 3 based on dicarbonylrhodium(I) shows nematic phase, while the complex 4 containing rhodium(I) bound to a COD ligand is a nonmesogen. The relationship between molecular structures and liquid crystal behavior has also been discussed by means of computer-aided molecular modeling.     

SYNTHESIS OF THE NOVEL CHIRAL POLYMERS WITH MULTIDENTATE LIGAND AND RESOLUTION OF DL-AMINO ACIDS

A new way for synthesizing styrenic type of chiral resins grafting to multidentate ligand has been found. The synthetic scheme is proved to be practical by means of elemental anaysis, IR spectra and metal adsorbility. The resolving power of the new chiral ligand resins coordinated with copper (Ⅱ) as stationary phases has been discussed based on HPLC, and some points of view about the compositions of mobil phase and mechanism of resolution are presented.     

Ring-opening polymerization of L-lactide with rare earth aryloxides substituted by various alkyl groups

<正>Rare earth aryloxides substituted by various alkyl groups[Ln(OAr)_3]such as methyl,isopropyl and tertbutyl,were used as single component catalysts to affect ring-opening polymerization of L-lactide(LLA).The catalytic activity, polymerization characteristics,polymerization kinetics and the mechanism were studied.It was found that the catalytic activity of rare earth aryloxides is influenced by both the structure and the number of alkyl groups on the phenyl ring.The stronger the electron-donation ability of the alkyl group,the higher the catalytic activity will be.An increase in the number of the substitute group will result in a higher catalytic activity.Lanthanum tris(2,4,6-tri-tert-butylphenolate)[La(OTTBP)_3] exhibits the highest activity among all lanthanum aryloxides.According to the ~1H-NMR data,it was proposed that the LLA polymerization proceeded via a coordination-insertion mechanism involving cleavage of acyl-oxygen bond of the lactide.