STUDIES ON CRYSTAL AND MOLECULAR STRUCTURES OF DEMETHYLCANTHARATE-M (M=Zn, Cu, Ni, Co)

The complexes of demethylcantharic acid coordinating with Zn~(2+), Cu~(2+), Ni~(2+) and Co~(2+) wereprepared and the five crystal structures were all determined by X-ray diffraction. Metal ions in thefive structures are of six-membered coordination. The demethylcantharate ions can act as a tri-,tetra- or penta-dentate ligand toward metal ions to form ion-pair structure, chain structure or threedimensional polymer structure respectively. The bridge oxygen atom in ligand always participatesin coordination. In the structures of KM(C_8H_8O_5)_2·6H_2O, the formal valence of M (Ni, Co) is+3, but the data of crystal structures show that M are M~(2+) ions and Ni may form a Ni~(2+) -stabilizedligand radical. In addition, the metal ions are assumed to be probes and some possible Interactionsbetween the acceptor and the receptor are discussed.     

Synthesis and Characterization of Poly-Ortho-Methylaniline With Different Degrees of Oxidation

Poly-ortho-methylanilines (POT) in three states fully oxidized, fully reduced and oxidized in varying degrees were synthesized by the reaction of common POT (C-POT) having nearly equal amounts of benzenediamine and quinonediimine units with iodine or phenylhydrazine, and the resulting polymers were characterized by IR,~(13)C-NMR, SEM and elemental analysis. The results showed that the quinonediimine unit in C-POT could be reduced by phenylhydrazine to the benzenediamine unit,forming the polymer with low OD (oxidation degree) or in a fully reduced state and that iodine-oxidation resulted in the increase of quinonediimine unit and decrease of benzenediamine unit. The solubility and flexibility of the formed polymers depend strongly on the amount of quinonediimine unit in it. It is necessary to reduce the content of quinonediimine structure unit in order to improve the solubility of aniline-class polymers.     

Synthesis and liquid crystalline behavior of side chain liquid crystalline polymers containing triphenylene discotic mesogens with different length flexible spacers

A series of side chain liquid crystalline polymers(SCLCPs) containing triphenylene(Tp) units in the side chains, denoted as PMTS(without spacer) and PMTn S(n = 2, 3, 4, 6, which is the number of the methylene units between the main chain and Tp moieties in the side chains), with different lengths of spacers were synthesized through conventional free radical polymerization. The chemical structures of the monomers were confirmed by 1H/13C-NMR, and the phase behaviors were examined by differential scanning calorimetry(DSC), polarized optical microscopy(POM) and wide-angle X-ray diffraction(1D and 2D WAXD). The molecular characterization of the polymers was performed with 1H-NMR, gel permeation chromatography(GPC) and thermogravimetric analysis(TGA). The phase behaviors of the polymers have been investigated by a combination of techniques including DSC, POM, 1D and 2D WAXD. The results showed that the length of spacer has significant effects on the LC phase behavior of polymers. For PMTS and PMT2 S, they displayed the columnar phase developed by the Tp moieties and the main chain as a whole due to the strong coupling effect of the Tp moieties and the main chain. For the PMT3 S, PMT4 S and PMT6 S, they formed the symmetry hexagonal columnar(ΦH) phase owing to the decoupling effect. All of these indicated that the "decoupling effect" or "coupling effect" depended on the length of spacers, leading to the different LC phase formation mechanism.     

QUANTUM CHEMICAL STUDY ON STRUCTURAL ACIDITY OF HZSM-5 ZEOLITE

The basic units of the framework structure of HZSM-5 zeolite are the five-membered rings which are linked by bridging oxygen atoms and as a result form units of four-membered rings or six membered rings. Semiempirical CNDO/2 quantum chemical method is used to calculate the charge density distribution for all these basic units, i.e., 4-, 5- and 6-membered rings of HZSM-5 zeolite. Quantitative relations between the structural parameter α_0 of the acidity of HZSM-5 zeolite and the number of aluminum atoms N_(Al) per unit cell are obtained. Zeolite may be considered as solids acting more or less as protonic polyacids in solution. This protonic acidity is expressed as activity, a_(H~+)= [H~+]f_(H~+) ,were =n_(H~+)aN_(Al)/Z_(cat) and the activity coefficient f_(H~+) is equal to a constant multiplied by the structural parameter, f_(H~+)= Kα_0, K is taken to be 32. Upder different (SiO_2/Al_2O_3) ratios, therefore, the protonic activities could be obtained theoretically, and the calculation results are essent     

Synthesis and characterization of dendronized hyperbranched polymers through the “A_3+B_2” approach

Dendronized hyperbranched polymer(DHP) is a new kind of polymer, which combines the advantages of dendrimers and hyperbranched polymers. In this work, two dendronized hyperbranched polymers, DHPG0 and DHPG1, were successfully prepared through the simple "A_3+B_2" type Sonogashira coupling reaction. The nonlinear optical(NLO) effects of DHPG0 and DHPG1, characterized by the d33 values, were 183 and 220 pm V~(–1) respectively, higher than those of their analogues of dendronized polymers and dendrimers, thanks to the special topological structure. Also, the obtained polymers displayed excellent solubility, good processability, and high thermal stability.     

Fabrication,structure and surface charges of albumin-chitosan hybrids

Protein-polymer hybrids consisting of protein and natural polymers or synthetic polymers exhibit superior properties to unmodified proteins,generating a high demand for these materials in the fields of medicine,biotechnology,and nanotechnology.Herein,protein-polysaccharide hybrids were fabricated via the formation of an amide bond between bovine serum albumin(BSA) and chitosan(CS) using N-ethyl-N-(3-dimethylaminopropyl) carbodiimide hydrochloride(EDC) as the couple reagent.FTIR spectrum reveals that the carboxyl group of BSA conjugated with the amino group of chitosan backbone.The molecular weight of BSA-CS hybrids was identified by matrix-associated laser desorption ionization time of flight mass spectra(MALDI-TOF MS) and sodium dodecyl sulfate polyacrylamide gel electrophoresis(SDS-PAGE).The maximum number of chitosan chains binding to each BSA molecule was estimated as 6,and the optimal number was estimated as 2.In addition,the secondary structure and surface property of BSA were dependent upon the number of polymer conjugating on protein.The secondary structure of BSA was not significantly changed,if a few chitosans were coupled with BSA.By further increasing the molar ratio of chitosan to BSA,the secondary structure of BSA was markedly damaged.The surface’s negative charges of modified BSA also decreased.The result of native polyacrylamide gel electrophoresis(native-PAGE) also demonstrated the changes in surface charges and molecular weight of BSA-CS hybrids.     

Synthesis and characterization of Bi-functional photorefractive polymers with high molecular weight and low glass transition temperature

Carbazole-based bi-functional photorefractive polyacrylates were prepared via free radical polymerization and post-azo-coupling reaction. The structure of polymers was characterized by Fourier transform infrared spectroscopy(FTIR) and proton nuclear magnetic resonance(1H-NMR) spectroscopy. The differential scanning calorimetry(DSC) and the thermal gravimetric analysis(TGA) were used to characterize the thermal property of polymers. The results indicate that though the glass transition temperature(Tg) of polymers increases with increasing the ratio of NLO groups, the polymers with different ratios of NLO groups still all show low glass transition temperatures around 60 °C, and good thermal stability, which are favorable to the practical application of these polymers. The gel permeation chromatographic(GPC) result indicates that these polymers all have high-molecular-weight which is favorable to the long term stability of the material. Further, these polymers have good solubility in chloroform solvent, and the solutions can easily be fabricated into optically transparent films. Gain coefficients of 75 cm-1, 185 cm-1 and 66 cm-1 can be observed at zero external electric field without any addition agent or pre-poling for polymers P-2, P-3 and P-4 respectively. The different contents of NLO groups result in the different properties of polymers P-2, P-3 and P-4.     

Synthesis and characterization of benzocyclobuten-4-yl acrylate monomer and its radical polymerization

<正>A benzocyclobuten-4-yl acrylate(1) monomer was prepared by esterification of 4-hydroxybenzocyclobutene with acryloyl chloride.The radical homopolymerization of 1 and copolymerization of 1 with styrene or n-butyl acrylate were carried out to produce linear polymers 2a,2b and 2c.Heating of these linear polymers under thermal initiation gave corresponding cross-linked polymers 3a,3b and 3c.The ring-opening reaction in the cross-linking process was confirmed by on-line infrared spectra.Differential scanning calorimetry showed that the glass transition temperatures of linear polymers 2a and 2b were 83.2℃and 68.1℃,respectively.Thermogravimetric analysis of the cross-linked polymers showed that they all exhibited good thermal stability.     

SYNTHESIS AND PROPERTIES OF NEW MESOGEN-JACKETED LIQUID CRYSTALLINE POLYMERS*

Some new mesogen-jacketed liquid crystalline polymers (MJLCP) with polymer backbones, spacers, andmesogenic units of different structures were synthesized by radical polymerization. The mesomorphic behavior of thesepolymers was examined using differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). Theirliquid crystallinity is influenced by the variation of polymer backbone, spacer, mesogenic unit and its terminal groups. Theresults show that 1) a more flexible polymer main-chain is more favorable to the formation of a liquid crystal phase, while 2)a flexible spacer will decrease the "Jacket Effect" and the liquid crystallinity and 3) a subtle modification of the terminalgroups on the mesogenic unit may also have a significant influence on properties of the polymers.     

Voltammetric determination of stability constants of lead complexes with diallyl disulfide,dimethyl disulfide,and diallyl sulfide

The complexation of Pb~(2+)by diallyl disulfide(DADS), dimethyl disulfide(DMDS) and diallyl sulfide(DAS)has been studied by differential pulse voltammetry. Stability constants,(log b), of the 1:1(PbL) and 1:2(PbL_2) complexes, where L = ligand, were found to be in the range of ca. 3.8–4.2 and 9.4–10.2,respectively. Complex formation is accompanied with a significant decrease in the peak current and the shift of the Pb2+/Pb half-wave potential to a higher one upon the addition of the sulfur containing ligands(L). The formation of 1:1 and 1:2 complexes, i.e., PbL~(2+)and PbL_2~(2+)was observed in the case of the three ligands. The consecutive formation constants of labile lead complexes with DADS, DMDS, and DAS were determined at 298 K by the method of De Ford and Hume. Apparently due to the large size of the lead ion,steric hindrance caused by the greater steric bulk of DADS compared to that of DMDS have little or no effects on the formation constants, so that very similar values were obtained in the case of the two ligands. Also, the possible participation of C=C double bonds in coordination with the metal center in the case of DADS appears to compensate for the steric effects caused by the larger size of this ligand. In agreement with the Jorgensen principle of symbiosis, the second formation constants were found to be approximately six orders of magnitude greater than the first ones.     

Quadruple Switching of Pleated Foldamers of Tetrathiafulvalene–Bipyridinium Alternating Dynamic Covalent Polymers

Two dynamic covalent polymers P1 and P2 were prepared by alternately linking electron‐rich tetrathiafulvalene (TTF) and electron‐deficient bipyridinium (BIPY²⁺) through hydrazone bonds. In acetonitrile, the polymers were induced by intramolecular donor–acceptor interactions to form pleated foldamers, which unfolded upon oxidation of the TTF units to the radical cation TTF^.+. Reduction of the BIPY²⁺ units to BIPY^.+ led to the formation of another kind of pleated secondary structures, which are stabilized by intramolecular dimerization of the BIPY^.+ units. The diradical dicationic cyclophane cyclobis(paraquat‐p‐phenylene) (CBPQT^2(.+)) could further force the folded structures to unfold by including the BIPY^.+ units of the polymers. Upon oxidation of the BIPY^.+ units of the cyclophane and polymers to BIPY²⁺, the first folded state was regenerated. Switching or conversion between the four conformational states was confirmed by UV/Vis spectroscopic experiments.     

Protonation-induced switching of pleated foldamers of diaminonaphthalene-bipyridinium polymers

1,5-diaminonaphthalene (DAN) and bipyridinium (BIPY²⁺) were copolymerized into NP1 and NP2 linked by acylhydrazone bonds. The formed intramolecular charge-transfer (CT) complex drove the linear foldamers to adopt pleated folding conformation. Upon protonation of the DAN units by triflic acid (TFSA), the pleated folding conformation unfolded to linear structure because of electron repulsion. And this linear structure can be refolded to pleated structure by titrating with triethylamine (TEA). 1,5-dinaphtho[38]crown-10 (DN38C10) can encapsulate bipyridinium group on the polymers after protonation. These processes were supported by UV–vis and fluorescence spectroscopy studies.     

光系统Ⅱ反应中心内组氨酸参与给体端次级电子转移反应的人工模拟ESR研究

对高等植物光系统皿(PS)反应中心的超分子模型化合物光诱导电子转移(PET)过程的研究主要集中在原初电子给体P。s。与其还原侧电子受体间的电子转移反应[‘’u．近年来,随着人们对高等植     

The discrimination between triplet state and radical cation in the pulse radiolysis of bithiophene in CCl4

The triplet state (³2T) and the radical cation (2T⁺√) of 2,2′-bithiophene (2T) are characterized by pulse radiolysis in CCl₄. Two main absorption bands at 360 and 420 nm are respectively attributed to ³2T* and to 2T⁺√. The triplet, induced in an excited state through a Förster mechanism, undergoes a conformational rearrangement (k₆=(6.8±0.9)×10⁶ s⁻¹). The radical cation is produced both through a resonance charge transfer and a second diffusional process; the two oxidizing species are respectively CCl₄⁺√ and (CCl⁺₃Cl⁻)_solv through the mediation of a singlet excited state, ¹2T*.     

荧烷染料的光诱导显色反应和机制的研究

荧烷染料是一类重要的功能性染料,广泛地应用于热敏和压敏记录材料.通常采用在酸作用下,使荧烷染料发生显色反应,由内酯环结构的无色体生成开环结构的有色体.并且通过吨环上不同取代基得到各种色调.荧烷染料有色体不稳定,在一般有机介质中容易发生褪色反应,使得荧烷染料作为记录介质普遍存在着色稳定性差、保存期短的缺点.为了改善有色体的稳定性,人们进行了大量的工作^[1-3],但均未取得重要进展.考虑到荧烷染料母核上带有烷胺基取代基,具有电子给体特性,有可能通过电子转移反应的途径进行显色反应.实现这种电子转移显色过程的关键问题是选择合适的电子受体.为此采用盐类化合物如碘盐和硫盐作为电了受体,因为它们容易和不同电子给体组成电子转移光敏反应体系^[4-6].因此,本文研究了以荧烷染料为电子给体和碘盐为电子受体的光致电子转移显色反应,并提出了显色反应机制.     

Optimised hydrothermal synthesis of multi-dimensional hybrid coordination polymers containing flexible organic ligands

In this paper, we summarise our recent research interest in the hydrothermal synthesis and structural characterisation of multi-dimensional coordination polymers. The use of N-(phosphonomethyl)iminodiacetic acid (also referred to as H₄pmida) in the literature as a versatile chelating organic ligand is briefly reviewed. This molecule plays an important role in the formation of centrosymmetric dimeric [V₂O₂(pmida)₂]⁴⁻ anionic units, which were first used by us as building blocks to construct novel coordination polymers. Starting with [V₂O₂(pmida)₂]⁴⁻ in solution, we have isolated [M₂V₂O₂(pmida)₂(H₂O)₁₀] species (where M²⁺ = Mn²⁺, Co²⁺ or Cd²⁺) via the hydrothermal synthetic approach, which were then employed for the construction of [CdVO(pmida)(4,4′-bpy)(H₂O)₂]·(4,4′-bpy)_0.5·(H₂O), [CoVO(pmida)(4,4′-bpy)(H₂O)₂]·(4,4′-bpy)_0.5, [Co(H₂O)₆][CoV₂O₂(pmida)₂(pyr)(H₂O)₂]·2(H₂O) and [Cd₂V₂O₂(pmida)₂(pyr)₂(H₂O)₄]·4(H₂O) by the inclusion of bridging organic ligands in the reactive mixtures, such as pyrazine (pyr) and 4,4′-bipyridine (4,4′-bpy). These materials can contain channel systems, and exhibit magnetic behaviour, not only due to the V⁴⁺ centres but also to the transition metal centres which establish the links between neighbouring dimeric [V₂O₂(pmida)₂]⁴⁻ anionic units. A closely related anionic moiety, [Ge₂(pmida)₂(OH)₂]²⁻, was engineered to allow the study of such crystalline hybrid materials using one- and two-dimensional high-resolution solid-state NMR.     

Preparation,Structure and Magnetic Properties of Lithium Substituted NiO by Molten Salt Method

A typical Li⁺ substituted NiO compound, Li_0.29Ni_0.71O, was synthesized by molten nitrate method. The effects of Li⁺ substitution on the structure and magnetic properties of NiO were investigated. X-Ray diffraction(XRD), scanning electron microscope(SEM) and high-resolution transmission electron microscope(HRTEM) analyses confirm the cubic structure of Li_0.29Ni_0.71O, with a primary particle size of 150 nm. Analysis of the Ni X-ray photoelectron spectroscopy(XPS) shows the transformation from Ni²⁺ to Ni³⁺ induced by Li⁺ substitution. Two magnetic transitions were observed at 225 and 55 K which were assigned to the ferrimagnetic ordering and spin glass transition, respectively. The different magnetic behavior with respect to that of NiO was attributed to the break of superexchange interaction Ni²⁺-O-Ni²⁺ and the formation of different spin clusters after non-magnetic Li⁺ doping.     

Fe掺杂g-C_3N_4的制备及其可见光催化性能

以硝酸铁和三聚氰胺为原料制备不同含铁量的Fe掺杂石墨氮化碳(g-C3N4).采用X射线衍射光谱(XRD)、紫外-可见(UV-Vis)光谱、傅里叶变换红外(FT-IR)光谱、电感耦合等离子体-原子发射光谱(ICP-AES)、荧光(PL)光谱、X光电子能谱(XPS)等分析手段对制备的催化剂进行了表征.结果表明,铁以离子形式镶嵌在gC3N4的结构单元中,影响了g-C3N4的能带结构,增加了g-C3N4对可见光的吸收,降低了光生电子-空穴对的复合几率.以染料罗丹明B的降解为探针反应系统研究了不同含铁量对g-C3N4在可见光下催化性能的影响.结果表明,m(Fe)/m(g-C3N4)=0.14%时,制备的Fe掺杂g-C3N4表现出最佳的光催化性能,120 min内罗丹明B的降解率高达99.7%,速率常数达到0.026 min-1,是纯g-C3N4的3.2倍.以叔丁醇、对苯醌、乙二胺四乙酸二钠为自由基(·OH)、自由基(O2-·)和空穴(h+VB)的捕获剂,研究了光催化反应机理.     

[(Me3Sn)2(Me3Sb)M(CN)6]∞ (M = Fe, Ru): Neuartige Organo-Sn/Sb-Polymere von besonderer chemischer und thermischer stabilität

The thermally (decomp. temp. 300°C) and completely air stable, novel coordination polymers [(Me₃Sn^IV)₂(Me₃Sb^V)M^II(CN)₆]_∞ with M = Fe and Ru can be prepared by co-precipitation from aqueous solutions of Me₃SnCl, Me₃SbBr₂ and K₄[(M(CN)₆], or, alternatively, by the ion-exchange-like reaction of the polymers [A(Me₃Sn)₃M(CN)₆]_∞ (A⁺ = Et₄N⁺, Cp₂Co⁺, Me₃Sn⁺ etc.) with Me₃SbBr₂. IR-spectroscopic findings suggest a statistical distribution of quasi-octahedral M(CN-Sn··)_6-x(CNSb ··)_x building blocks (with x = 0–6) within a three-dimensional network.     

BSA与羟磷灰石相互吸附的FTIR-ATR光谱

采用傅里叶变换红外衰减全反射(FTIR-ATR)光谱法对牛血清白蛋白(BSA)在羟磷灰石(HA)[Ca₁₀(OH)₂(PO₄)₆]表面不同时间的相互吸附作用进行了表征。在BSA溶液作用下,羟磷灰石表面的Ca²⁺、PO₄^3-和OH^-离子初始的溶解和再沉淀使得BSA与HA相互作用层层叠加,在HA表面形成从表层到次表层分子都包含有吸附的BSA的覆盖层,从而加深两者之间的相互作用。经红外差谱法处理过的相关ATR数据表明, BSA与HA之间的相互作用是快速的,并随时间变化进一步加强;来自HA上PO₄^3-的P=O基团对蛋白质肽键的酰胺II带(―CNH)、多肽链的甲基(―PO₃)和亚甲基(―CH₂)上氢的吸附作用要比P―O快速而且强烈。Ca²⁺在该吸附过程中起了极其重要的作用,其快速与蛋白质肽键的羰基氧发生作用,并诱导该蛋白质二级结构由β-折叠向α-螺旋和β-转角构象转变;伴随着这一构象变化,蛋白质多肽链上大多数肽键的―C=O和H―N―活性基团从链间氢键交联中释放出来,带动众多的氢分别参与同HA表面的Ca²⁺、PO43-和OH^-离子的相互吸附作用,并牢牢地结合于HA表面;这对硬组织的再生起着重要作用,促进了HA的生物矿化过程。