Studies on Cobalt-Carbon Cluster——Svntnesis of α-Naphthyl α-Thienyl and Substituted-Phonyl Phenylacetyene Dicobalt Hexacarbonyls

12 new diarylacet ylenedicobal t hexacarbonyl complexes were synthesized by complexation reaction of a-naphthyl,a-thienyl or sub-stituted-phenyl phenylacetylene with Co2CO)8 and N-acetylation ofp-aminophenyl phenylacetylenedicobalt hexacarbonyl.The structures of all the complexes were characterized by elemental analysis,IR and H NMR spectroscopy.Making a comparison between the N-acetylation of p-aminophenyl phenylacetylenedicobalt hexacarbonyl and that of aniline under comparable conditions,we found that the clustercore PhC2Co2(CO)6 para to an amino group attached to aromatic ring does not obviously affect the nucleophilicity of aniline.     

KINETICS AND MECHANISM OF PHOTOINDUCED POLYMERIZATION BY α,α-DIMETHOXY-α-PHENYL ACETOPHENONE

α,α-dimethoxy-α-Phenyl acetophenone (DMPA) is an efficient and thermally stable photoinitiator. Here its spectral characteristics in the transient state were shown. The transient species were identified as a benzoyl radical and a dimethoxyi benzyl radical that played a primary initiation role in polymerization. The kinetics and mechanism of the bulk polymerization of MMA were investigated. The exponent of DMPA concentration and k_p/k_1~(1/2) value were found to be 0.5 and 0.066 mol(-1/2)l~(1/2)s~(-1/2), respectively. The existence of oxygen led to obtain the polymer with higher molecular weight, which can be attributed to the occurrence of the subsequent polymerization induced by active polymer end group. In the photocrosslinking reaction, the dependence of DMPA content on initial rate has been found. A principal reason is that the sample contained higher percentage of DMPA has higher light-absorbed efficiency. In solid film, higher concentration of DMPA is permitted to be used because there is little excited state self-quenching effect in the rigid medium.     

Synthesis, properties and electropolymerization of starshaped oligothiophenes with hexakis(fluoren-2-yl)benzene as core

Star-shaped oligothiophenes with hexakis(fluoren-2-yl)benzene (HFB) as cores were designed and synthesized. Grafting thiophene units to HFB results in a bond flattening of the core, and makes the molecules a flipping-twist shape. Their thermal, photophysical and electrochemical properties were studied. Highly cross-linked conjugated polymers can be produced by electropolymerization of T1-T3.     

Converting Thiophene in Simulated Coking Crude Benzene to N,N-Dimethyl-2-thiophenecarboxamide by Dimethylcarbamyl Chloride Under Mild Conditions

Since the content of thiophene in coking crude benzene is high, it is necessary to remove it from coking crude benzene for efficient utilization. In this study, an important intermediate, N,N-dimethyl-2-thiophenecarboxamide, was synthesized from thiophene and dimethylcarbamyl chloride. The influences of the dosages of dimethylcarbamyl chloride and ZnCl2 catalyst, reaction temperature and time on the removal rate were further explored based on the reaction kinetics.The structure of the target product was characterized by means of MS,NMR and 13C NMR.The removal rate of thiophene was 98.14% after the reaction for 2 h and thiophene was almost removed after the reaction for 3 h under the optimal reaction conditions [a molar ratio of n(thiophene):n(dimethylcarbamyl chioride):w(ZnCl2)=1:12:10,300 r/min, 318 K and 101.325 kPa].The acylation of thiophene with dimethylcarbamyl chloride was approximately in accord with the first order kinetic equation at 303-323K.The activation energy was 53.9850 kJ/mol and the pre-exponential factor was 1.4521×10^9 h^-1.     

CRITICAL CONCENTRATIONS OF α(1→3)-D-GLUCAN FROM LENTINUS EDODES IN NaOH AQUEOUS SOLUTION

Critical concentrations of α-(1→3)-D-glucan L-FV-Ⅱ from Lentinus edodes were studied by viscometry andfluorescence probe techniques. The dependence of the reduced viscosity on concentration of the glucan in 0.5 mol/L NaOHaqueous solutions with or without urea showed two turning points corresponding to the dynamic contact concentration c_s andthe overlap concentration c~* of the polymer. The values of c_s and c~* were found to be 1×10~(-3) g cm~(-3) and 1.1×10~(-2) g cm~(-3),respectively, for L-FV-Ⅱ in 0.5 mol/L NaOH aqueous solutions. The two critical concentrations of L-FV-Ⅱ in 0.5 mol/LNaOH aqueous solutions were also found to be 1.2×10~(-3) g cm~(-3) fbr c_s and 9.2×10~(-3) g cm~(-3) for c~* from the concentrationdependence of phenanthrene fluorescence intensities. The overlap concentration c~* of L-FV-Ⅱ in 0.5 mol/L NaOH aqueoussolutions was lower than that of polystyrene with same molecular weight in benzene, owing to the fact that polysaccharidetends to undergo aggregation caused by intermolecular hydrogen bonding. A normal viscosity behavior of L-FV-Ⅱ in 0.5 mol/L urea/0.5 mol/L NaOH aqueous solutions can still be observed in an extremely low concentration range at 25℃.     

DFT Investigation on Spectroscopic Characteristics and Photolysis Mechanisms of α-Phenoxylacetophenone

The photoinduced bond cleavage and quenching of the α-phenoxylacetophenone excitation states can serve as a template to investigate fundamental photochemical processes. In this work, the absorption and emission spectra as well as the photodecomposition mechanisms of α-phenoxylacetophenone were studied. The density functional theory(DFT) calculations revealed that: 1) the absorption spectra in methanol obtained by the M06-2X functional agree well with those by the B3LYP one; 2) the wavelength of the strongest peak acquired with the B3LYP method is slightly higher than the M06-2X one by 20.07 nm; 3) the βC–C bond in S_1 can be broken directly.     

LOW POTENTIAL ELECTROPOLYMERIZATION OF ANISOTROPIC CONDUCTIVE POLYTHIOPHENE FILMS AND FABRICATION OF ELECTRICAL DEVICES

The complexation of thiophene with a Lewis acid with moderate acidity as a solvent, such as BF_3-ethyl ether (BFEE) remarkedly lowered the electrochemical polymerization potential. The positively chargedmetal surface of electrode in the process of electrochemical deposition enhanced the coordination interactionbetween π-electrons of thiophene unit and the metal, which makes thiophene rings lie parallel to the surfaceof electrode, resulting in a highly ordered polymeric structure. Because of the large intra-chain transferintegrals, the transport of charge is believed to be principally along the conjugated chains, which is muchgreater than the inter-chain hopping. The specific electrical resistance across the polythiophene film thicknessis more than 10~4 times than that along the surface plane of the film. In this paper we review the recentdevelopment of polymerization technique by low potential electrochemical method performed in our lab andseveral electrical devices in which the compact polythiophene films, such as anionic and cationic sieves, andlaminate film junction of undoped polythiophene derivatives were used.     

THE SYNTHESIS OF PHOSPHORAMIDOTHIOATES AND THEIR QUANTITATIVE STRUCTUREACTIVITY CORRELATIONS

O-Aryl O-ethyl N-isopropyl phosphoramidothioates (Ⅰ) have herbicidal activity. In order to study the relationship between structures and activities of these compounds, more than thirty compounds (Ⅰ) have been prepared by the reaction of O-aryl O-ethyl phosphorochloridothioates with isopropylamine in the presence of 40% NaOH at 0℃. The intermediates, phosphorochloridothioates, were prepared separately from a large excess of O-ethyl Phosphorodichloridothioate and various substituted phenols in the presence of 40% NaOH and a catalyrical amount of Et_3N at 0—5℃. As a result, higher purity and good yields were obtained.It was found that the activity of these compounds was highly dependent upon the substituents attached to the benzene ring with respect to the characteristic parameters π, E_s, σ and F by using Hansch's equation.It was indicated that hydrophobic (π), steric (E_s), and electronic (σ and F) effects of the substituents on the ring in those molecules seem to be of considerable importance i     

Copolymerization of α-Methylstyrene and Styrene

In this paper, the effects of temperature from 60 °C to 80 °C and the molar ratios in monomer feed on the copolymerization of α-methylstyrene(AMS) and styrene(St) were studied. The resulting copolymers, designated as PAS, were characterized by FTIR, GPC, NMR and TGA. When the reaction temperature was below 75 °C, the molecular weights increased almost linearly as the evolution of the copolymerization. The phenomenon revealed that AMS could mediate the conventional free radical polymerization having some features of a controlled system. As the AMS/St = 50/50(molar) in feed, the overall fraction of the AMS unit incorporated into the copolymer was as high as 42 mol%, the monomer conversion could be more than 90 wt% and the molecular weights could reach as high as 4400. However, since the styrene is more reactive than AMS, the AMS fraction in copolymer increased with the overall monomer conversion. The 13C-NMR revealed the products were random copolymers which had triads, such as-AMS-AMS-AMS-,-St-AMS-AMS-(-AMS-AMS-St-) and-St-AMS-St-. TGA curves demonstrated that the degradation temperature of the resulting copolymers went down from about 356.9 °C(0 mol% AMS) to 250.2 °C(42 mol% AMS). This behavior demonstrated that there exist weak bonds in the AMScontaining sequences which could be used as potential free radical generators.     

SYNTHESIS AND POLYMERIZATION OF α-METHACRYLYOXYLETHYLOXYCARBONYLMETHYL-ω-(N,N-DIETHYLDITHIOCARBAMYL)POLYSTYRENE MACROMONOMERS

Polystyrene macromonomers with different molecular weight were prepared by radical polymerization of styrene(St) in benzene using β-methacryloxylethyl 2-N,N-diethyldithiocarbamylacetate (MAEDCA) as a monomer-iniferter.Characterization of the macromonomer by ~1H-NMR showed that the end groups were α-methacrylyoxylethyloxycarbonyl-methyl and ω-(N,N-diethyldithiocarbamyl). The macromonomer was difficult to homopolymerize, but it was easilycopolymerized with methyl methacrylate (MMA) initiated by AIBN to form graft copolymers (PMMA-g-PSt) with PStbranches randomly distributed along the PMMA backbone. Copolymerization reaction and the structure of the graftcopolymers were strongly affected by M_n and concentration of the macromonomer. The composition and M_n of the purified graft copolymer were determined by ~1H-NMR and GPC analysis.     

The Concentration of Hydrogen Peroxide Generated during Aggregation of α-Synuclein in vitro Is Lower than 5 nmol／L

Using a fluorometric method with a detection limit of 5 nmol/L, here it is reported that albeit positive results were got from bovine serum albumin (BSA) and chicken ovalbumin (OVA) as published in literature, no detectable amount of hydrogen peroxide (H2O2) was generated during α-synuclein (α-Syn) aggregation in vitro even in the presence of transition metal ions Cu(Ⅱ) or Fe(Ⅲ). The results suggest that the concentration of H2O2 generated during aggregation of α-Syn in vitro be lower than 5 nmol/L beyond the detection limit of the adopted method and it is far too poor to be responsible for the cytotoxicity of α-Syn aggregates, thus allowing people to extensively elucidate the mechanism underlying neurotoxicifies of the aggregates formed by some amyloidogenic proteins.     

PROTON NUCLEAR MAGNETIC RESONANCE AND ELECTRON PARAMAGNETIC RESONANCE INVESTIGATION OF α-α CROSS-LINKED Fe-Co HYBRID HEMOGLOBINS

The following asymmetric α1 99 Lys-α2 99 Lys cross-linked Fe(Ⅱ)-Co(Ⅱ) hybrid hemoglobins (Hbs) were first prepared from derivatives of hemoglobin C (β6 Glu-Lys) and human normal HbA: [α(Co)β(Fe)]A[α(Co)β(Co)]cXL, [α(Fe)β(Co)]A[α(Co)β(Co)]cXL, etc.Their 500 MHz 1H NMR and EPR spectra were measured in order to study the change in their tertiary and quaternary structure under atmosphere of deozy, oxy and carbon monoxide (with or without IHP). From the change of T and R marks in 1H NMR hydrogen bonding region, it is proved that oxygen molecules are first bonded to α(Fe) subunits rather than to β(Fe). The experimental phenomena provided further evidence that intermediate states of ligation are present in addition to T and R state during process of binding of oxygen to Hb. IHP facilitates transformation of T state to R state. The same conclusion can also be drawn from the results of EPR spectra at 77 K.     

Two-dimensional correlation analysis of continuous online in situ ATR-FTIR on the adsorption of butyl xanthate at the surface of α-PbO

The adsorption behavior of butyl xanthate on the surface of lead oxide was investigated using continuous online in situ attenuated total reflectance Fourier transform infrared(ATR-FTIR) spectroscopy technique and two dimensional(2D) correlation analysis.The adsorbed layer studied was prepared by coating α-PbO particles onto the surfaces of the ZnSe crystal.The appearance of spectral peaks at 1203 cm~(-1),1033 cm~(-1) and their red shift indicated the formation and aggregation of xanthate at the surface of α-PbO.According to 1R intensity changes after rinsing with deionized water and a NaOH solution,the adsorption was proved to be a chemisorption type.The competition between xanthate and OH for the surfaces leads to desorption of xanthate at higher pH.The technique of 2D correlation ATR-FTIR spectroscopy was used to evaluate the changing order of spectral intensities in the adsorption process,and the results indicated that xanthate micelles were formed at the surfaces.The adsorption kinetics of butyl xanthate was found to be a pseudo-second-order reaction model and the adsorption capacity of butyl xanthate at α-PbO was as high as 281 mg g~(-1) after 150 min.     

Kinetics and Mechanism of the Photo-oxidation of Thiophene by O2 Adsorbed on Molecular Sieves

Photochemical oxidation of thiophene in n-octane/water extraction system using O2 as oxidant was studied. The reaction mechanism ofthiophene oxidation was proposed. Results obtained here can be used as the reference for the oxidative desulfurization of gasoline because thiophene is one of the main components containing sulfur in fluid catalytic cracking gasoline. Thiophene dissolved in n-octane was photodecomposed and removed into the water phase at ambient temperature and atmospheric pressure. A 500 W high-pressure mercury lamp （main wave length 365 nm, 0.22 kW/m） was used as light source for irradiation, and air was introduced by a gas pump to supply O2. Thiophene can be photo-oxidized to sulfone, oxalic acid, SO4^2-, and CO2. The desulfurization yield of thiophene in n-octane is 58.9% under photo-irradiation for 5 h under the conditions of air flow at 150 mL/min and V（water）：V（n-octane）=1：1. It can be improved to 92.3% by adding 0.15 g zeoliteartificial into 100 mL reaction system, which is the adsorbent for O2 and thiophene. And under such conditions, the photo-oxidation kinetics of thiophene with O2/zeoliteartificial is first-order with an apparent rate constant of 0.5047 h^-1 and a half-time of 1.37 h. The sulfur content can be depressed from 800 μL/L to less than 62 μL/L.     

Synthesis of α-Bromine- Terminated Polystyrene Macroinitiator and Its Initiation of MMA Polymerization by ATRP

In the present paper the synthesis of block copolymers via the transformation from living anionic polymerization (LAP) to atom transfer radical polymerization (ATRP) was described. Α-Bromine-terminated polystyrenes(PStBr) in the LAP step was prepared by using n-BuLi as initiator, tetrahydrofuran (THF) as the activator, α-methylstyrene (α-MeSt) as the capping group and liquid bromine (Br2) as the bromating agent. The effects of reaction conditions such as the amounts of α-MeSt, THF, and Br2 as well as molecular weight of polystyrene on the bromating efficiency (BE) and coupling extent (CE) were examined. The present results show that the yield of PStBr obtained was more than 93.8% and the coupling reaction was substantially absent. PStBr was further used as the macroinitiator in the polymerization of methyl-methacrylate(MMA) in the presence of copper(Ⅰ) halogen and 2,2-bipyridine(bpy) complexes. It was found that the molecular weight of the resulted PSt-b-PMMA increased linearly with the increase of the conversion of MMA and the polydispersity was 1.2-1.6. The structures of PStBr and P(St-b-MMA) were characterized by 1H NMR spectra.     

DIRECT CONNECTIONS BETWEEN HYPOTHALAMUS AND LUMBAR SPINAL CORD IN RABBITS

Horseradish peroxidase (HRP) was injected into the L6 spinal cord in seven rabbits andthe labeling in the hypothalamus traced. The distribution of the retrogradely labeled cellswas studied and the anterogradely labeled fibers and terminal branches were unequivocallyidentified. Hypothalamo-spinal projection cells were found predominantly on the ipsilateral side,mainly distributed in the posterior, dorsal, and lateral hypothalamic areas, and the paraven-tricular nucleus. Some were found in the perifornical nuelcus and a few could be seen in thetuber area, supranmmnfillary nucleus and tho region doisal to the supraoptic nucleus. Spino-hypothalamic projections were found to terminate mainly on the contralateral sidevia two. routes: (i) The dorsal longitudinal fascieulus, distributed to the posterior hypotha-lamie area. Some might end in the supramammillary nucleus; (ii) Fibers running latero-medially ventral to the mammillothalamic tract to terminate in the dorsal parts of the medialand lateral hypothalanms     

ORGANO-SOLUBLE FLUORINATED POLYIMIDES DERIVED FROM α,α-BIS(4-AMINO-3,5-DIMETHYLPHENYL)-4''''-FLUOROPHENYL METHANE AND VARIOUS AROMATIC DIANHYDRIDES

Organo-soluble fluorinated polyimides were synthesized by the polycondensation of a new aromatic diamine α,α-bis(4-amino-3,5-dimethylphenyl)-4'-fluorophenyl methane with several aromatic dianhydrides.The one-step polymerizationprocedure was conducted at 180℃in m-cresol,producing the polyimides with inherent viscosities of 0.68-0.76 dL.g~(-1).Thepolyimides could be soluble not only in polar aprotic solvents,such as N-methyl-2-pyrrolidinone,and N,N-dimethylacetamide,but also in common organic solvents,such as chloroform,cyclopentanone,m-cresol and so on.Thepolyimide films show excellent transparency with the UV-Vis cut-off lengths of 310-360 nm and light transmittances ofhigher than 80% in the visible region.In addition,the polyimides exhibit good thermal stability with an initial decompositiontemperature(T_d)higher than 530℃and have more than 60% of residual weight retentions at 700℃.     

Ru-catalyzed highly enantioselective hydrogenation of α-keto Weinreb amides

Asymmetric hydrogenation of α-keto Weinreb amides has been realized with [Ru((S)-Sunphos)(benzene)Cl]Cl as the catalyst and CeCl 3·7H2O as the additive.A series of enantiopure α-hydroxy Weinreb amides(up to 97% ee) have been obtained.Catalytic amount of CeCl3·7H2O is essential for the high reactivity and enantioselectivity and the ratio of CeCl3·7H2O to [Ru((S)-Sunphos)(benzene)Cl]Cl plays an important role in the hydrogenation reaction.     

Study on the Nanosized Amorphous Ru-Fe-B/ZrO2 Alloy Catalyst for Benzene Selective Hydrogenation to Cyclohexene

A novel nanosized amorphous Ru-Fe-B/ZrO2 alloy catalyst for benzene selective hydrogenation to cyclohexene was investigated. The superior properties of this catalyst were attributed to the combination of the nanosize and the amorphous character as well as to its textural character. In addition, the concentration of zinc ions, the content of ZrO2 in the slurry, and the pretreatment of the catalyst were found to be effective in improving the activity and the selectivity of the catalyst.     

SYNTHESIS AND CHARACTERIZATION OF ORGANSOLUBLE POLYIMIDE AND COPOLYIMIDES FROM ALICYCLIC DIANHYDRIDE

A kind of highly organsoluble polyimide and copolyimides were successfully synthesized from bicyclo（2.2.2）-oct- 7-ene-2,3,5,6-tetracarboxylic dianhydride （BCDA）, the commercial diamine 4,4＇-methylenedianiline （MDA） and the designed diamine 4,4＇-methylenebis-（2-tert-butylaniline） （MBTBA）. The polyimide from BCDA and MBTBA is highly soluble in conventional low boiling point solvents （such as chloroform, tetrahydrofuran） at room temperature. But the solubility of the copolyimides in conventional solvents decreased with the molar ratio of MBTBA and MDA decreased. When the molar ratio of MBTBA and MDA was larger than 7/3, the copolyimides can be soluble in low boiling point solvents at room temperature to form a transparent, flexible, tough film by solution casting. When the molar ratio of MBTBA and MDA was between 7/3 and 1/9, they can only be soluble in hot dipolar aprotic solvents （such as DMF, NMP etc.） and form films too. The copolyimide was only soluble in m-cresol when the molar ratio of MBTBA and MDA was lower than 1/9. The number-average molecular weights of the soluble copolyimides were larger than 5.8 × 1064 g/mol by GPC and their polydispersity indices were higher than 1.4. Only one glass transition temperature of these copolyimides was detected around 400℃ by DMA. The copolyimides did not show appreciable decomposition up to 430℃ in N2.