POLYIONIC COMPLEXES DERIVED FROM POLYVINYL ALCOHOL Ⅰ. PREPARATION AND THEIR SOLVATION BEHAVIOR*

Polycations and polyanions of polyvinyl alcohol (PVA) with various substitution degrees were pre-pared by acetalization of PVA with aldehyde derivatives such as p-formylbenzoic acid, glyoxalic acid, p-formyl-benzenesulfonic acid, p-formylpyridine, and p-dimethylaminobenzaldehyde and then neutral-ized or quaternarized with methyl iodide. The corresponding PVA type polyionic complexes wereobtained by mixing the aqueous solutions of these polycations and polyanions. The solvation behaviourof these polyionic complexes were investigated. It was found that the H_2O-DMF-NaSCN solventsystem is superior to the H_2O-DMF-NaBr system for these PVA type polyionic complexes.     

Estimation of the desorption energy of dichloromethane and water in MIL-53 by DSC and ab-initio calculations

Desorption energies of dichloromethane(CH_2Cl_2) and water(H_2O) in a metal-organic framework, MIL-53(Al), were investigated by the combination of experimental(differential scanning calorimeter, DSC) and computational(ab-initio calculations) methods. The differences of desorption energy and natural log of the frequency factor of CH_2Cl_2 and H_2O in MIL-53(Al) were analyzed by a thermo active process using DSC measurements. The interaction energy of guest molecules with MIL-53(Al), which corresponds to the desorption in the thermal active process, was explored using ab-initio calculation. As a result of the difference in the interaction energies of H_2O and CH_2Cl_2 in MIL-53(Al), the site near the μ_2-OH groups has two potential wells. Both experimentally and computationally, MIL-53 presents the preferential adsorption of CH_2Cl_2 than H_2O.     

Challenges and opportunities for using formate to store,transport, and use hydrogen

In this perspective article,the synthesis and thermodynamic properties of aqueous solutions of formate salts(FS,HCO_2~-)are described in relationship to the concept of H_2carriers.The physiochemical properties of solid FS,aqueous formate solutions,and aqueous bicarbonate solutions set the limitations for storage capacity,deliverable capacity,and usable H_2capacity of these H_2carriers,respectively.These parameters will help in the design of systems that use H_2carriers for storage and transport of H_2for fuel cell power applications.FS,as well as admixtures with formic acid(FA,H_2CO_2),have potential to address the goals outlined in the U.S.Department of Energy’s H2@scale initiative to store in chemical bonds a significant quantity of energy(hundreds of megawatts)obtained from large scale renewable resources.     

Syntheses,Crystal Structures,and Magnetic Properties of Mn(Ⅱ) and Co(Ⅱ) Coordination Polymers Constructed from Pyridine-tricarboxylate Ligand

Two coordination polymers, namely {[Mn(HL_1)(phen)]·4H_2O}_n(1) and [Co_2(HL_2)_2(H_2O)_2]_n(2) have been constructed hydrothermally using H_3L_1 and H_3L_2(H_3L_1 = 2-(5-carboxypyridin-2-yl)terephthalic acid, H_3L_2 = 2-(4-carboxypyridin-3-yl)terephthalic acid), phen, MnCl_2×4H_2O and CoCl_2×6H_2O. The products were isolated as stable crystalline solids and were characterized by IR spectroscopy, elemental, thermogravimetric(TGA), powder(PXRD) and single-crystal X-ray diffraction analyses. Compound 1 features a 3D framework structure, which was topologically classified as a trinodal 4,6,6-connected net with the unique topology defined by the point symbol of(3~(10).5.6~4)4(3~(10).6.7~4)2(5.6~2.8~2.9). Compound 2 possesses a 2D metal-organic layer, which was topologically classified as a binodal 4,4-connected layer defined by the point symbol of(4~3.6~2.8). The layers are further extended into a 3D supramolecular framework via hydrogen bonds. The magnetic properties for both compounds were also investigated, indicating antiferromagnetic interactions between the adjacent metal ions.     

Complexation of radionuclide ~(152+154)Eu(Ⅲ) with alumina-bound fulvic acid studied by batch and time-resolved laser fluorescence spectroscopy

To contribute to the understanding of Eu(Ⅲ)interaction properties on hydrous alumina particles in the absence and presence of fulvic acid(FA),the complexation properties of Eu(Ⅲ)with hydrous alumina,FA and FA-alumina hybrids are studied by batch and time-resolved laser fluorescence spectroscopy(TRLFS)techniques.The continuous increase in the fluorescence lifetime of Eu-alumina and Eu-FA with increasing pH indicates that the complexation is accompanied by decreasing number of hydration water in the first coordination sphere of Eu(Ⅲ).Eu(Ⅲ)is adsorbed onto alumina particles as outer-sphere surface complexes of≡(Al-O)-Eu·(OH)·7H_2O and≡(Al-O)-Eu·6H_2O at low pH values,and as inner-sphere surface complexes as≡(Al-O)_2-Eu~+·4H_2O at high pH.In FA solution,Eu(Ⅲ)forms complexes with FA as(COO)_2Eu~+(H_2O)_x and the hydration water number in the first coordination sphere decreases with pH increasing.The formation of≡COO-Eu-(O-Al≡)·4H_2O is observed on FA-alumina hybrids,suggesting the formation of strong inner-sphere surface complexes in the presence of FA.The surface complexes are also characterized by their emission spectra[the ratio of emission intensities of~5D_0→~7F_1(λ=594nm)and~5D_0→~7F_2(λ=619nm)transitions]and their fluorescence lifetime.The findings is important to understand the contribution of FA in the complexation properties of Eu(Ⅲ)on FA-alumina hybrids that the clarification of the environmental behavior of humic substances is necessary to understand fully the behavior of Eu(Ⅲ),or its analogue trivalent lanthanide and actinide ions in natural environment.     

SYNTHESES AND STRUCTURES OF POLYPHENYLSILSESQUIOXANES

Phenyltrichlorosilane was hydrolyzed both ifi. toluene and in ether from which two kinds of prepolymers were obtained with different structures, molecular weights, and molecular weight distributions. Polymers were prepared from the prepolymers in various polymerization conditions. The ladderlike, branched, and crosslinked structures formed under different polymerization conditions were characterized by means of FTIR, ~1H and ~(29)Si-NMR, and elemental analysis. Azeotropic distillation of solvents and H_2O formed during polymerization was found useful in removing H_2O from the system and high molecular weight products with perfect ladderlike structure were obtained.     

Chelating agents role on phase formation and surface morphology of single orthorhombic YMn2O5 nanorods via modified polyacrylamide gel route

YMn2O5nanorods were synthesized through a modified polyacrylamide gel route.The synthesis strategy in this work is based on a sol-gel process using a polyacrylamide gel method in which oxalic acid,citric acid or tartaric acid is employed as the chelating agent.In the gel routes,oxalic acid was used as a carboxyl chelating agent,while citric acid or tartaric acid was a carboxyl and hydroxyl chelating agent.The as-prepared samples were characterized by means of techniques such as X-ray powder diffraction(XRD)measurement,thermogravimetric analysis(TG),differential scanning calorimetry analysis(DSC),Fourier transform infrared spectroscopy(FTIR),X-ray photoelectron spectroscopy(XPS),thermal expansion measurement and field-emission scanning electron microscopy(SEM)investigations.It was found that oxalic acid is the best chelating agent with Y(NO3)3·6H2O and Mn(CH3COO)2·4H2O as precursors to prepare a single orthorhombic YMn2O5nanorods at 1000°C.Scanning electron microscope observation shows that the morphology of YMn2O5powders is significantly dependent on the chelating agent.The peaks(single orthorhombic YMn2O5nanorods)at 642,600,573,546,521,493,486,468,448 and 400cm?1were observed from FTIR spectra.The phase,surface morphology and chelation mechanisms of YMn2O5samples have been discussed on the basis of the experimental results.     

Syntheses,Structures and Catalytic Properties of Two Mn(Ⅱ) and Cd(Ⅱ) Coordination Polymers through in Situ Ligand Reaction

Two coordination polymers, namely [Mn(μ-Hcpia)(bipy)(H_2O)_2]_n(1) and [Cd_3(μ_3-Hcpia)_2(μ-Hbiim)_2(μ-H_2biim)(H_2O)_2]_n(2), have been constructed hydrothermally using H_2cbia(H_2cbia = 5-(4'-cyanobenzoxy)isophthalic acid), bipy(bipy = 4,4'-bipyridine), H_2biim(H_2biim = 2,2'-biimidazole), and manganese or cadmium chlorides at 160℃. Interestingly, the H_3cpia(H_3cpia = 5-(4'-carboxylphenoxy)isophthalic acid) ligand was generated by in situ hydrolysis of cyano group in H_2cbia. The products were isolated as stable crystalline solids and were characterized by IR spectra, elemental analyses, thermogravimetric analyses(TGA), and single-crystal X-ray diffraction analyses. Both compounds crystallize in the triclinic system, space group P1. Compound 1 discloses a 1D linear chain of the 2C1 topological type. Adjacent chains are assembled into a 2D supramolecular sheet through O–H···O/N hydrogen bonds. Compound 2 features a 3D framework with a 3,4,4 T25 topology. The luminescent and catalytic properties of two compounds were investigated. Compound 1 exhibits a superior catalytic activity in the cyanosilylation at room temperature.     

FTIR–ATR in situ observation on the efflorescence and deliquescence processes of Mg(NO_3)_2 aerosols

The efflorescence and deliquescence processes of Mg(NO3)2 aerosol particles deposited on ZnSe substrate have been investigated through in situ Fourier transform infrared-attenuated total reflection (FTIR-ATR) technique at the molecular level. At relative humidity (RH) of ~3%, Mg(NO3)2 particles existed as amorphous states. The amorphous Mg(NO3)2 particles were transformed into crystalline Mg(NO3)2·nH2O (n ≤ 5) with slight increasing of RH. Thermodynamically stable Mg(NO3)2·6H2O crystals were gradually formed on the particle surface and started to be dissolved at the saturation point (~53% RH). At the same time, a continuous phase transition from Mg(NO3)2·nH2O (n≤5) to Mg(NO3)2·6H2O occurred on the particle surface. This led the solid particles to completely deliquesce at 76% RH, which was much higher than the saturation point of 53% RH. In the efflorescence process, Mg(NO3)2 droplets entered into the supersaturated region due to the gradual evaporation of water. Finally, amorphous particles were formed when RH decreased below 5%. In the FTIR-ATR spectra of the supersaturated Mg(NO3)2 droplets, the absorbance of the symmetric stretching vibration of NO3- (v1- NO-3) clearly became stronger. It resulted from the continuous formation of solvent share ion pairs (SIPs), and even the contact ion pairs (CIPs) between Mg2 and NO3.     

Synthesis of La(Ⅲ), Y(Ⅲ) complexes with polyglycol aldehyde-amino acid Schiff base and their high resolution solid state ~(13)C NMR spectra

La(Ⅲ), Y(Ⅲ) complexes with diglycol aldehyde bis-arginine (H_2DAAR) and tetraglycol aldehyde bislysine (H_2TALY) Schiff bases were synthesized. They were characterized and formulated as La(H_2DAAR) (NO_3)_3·6H_2O and Y (H_2TALY)(NO_3)_3·5H_2O separately by elemental analyses. The obtained complexes were investigated in detail by high resolution solid state (HRSS) ~(13)C NMR using cross polarization, magic angle spinning (CPMAS), and total suppression of sidebands (TOSS)techniques. The results are supported by the liquid state 2D-~1H-~(13)C COSY NMR spectra. Some new information about the splitting peaks of ~(13)C for—CH=N—group and alkene carbon bands, etc. in HRSS ~(13)C NMR spectra are given.     

Synthesis,Characterization and Standard Molar Formation Enthalpy of [Sm(C_7H_5O_3)_2(C_4H_6NO_2S)]·2H_2O

[Sm(C7H5O3)2(C4H6NO2S)]·2H2O was synthesized from the reaction of samarium chloride hexahydrate with salicylic acid and thioproline,and characterized by IR,elemental analysis and thermogravimatric analysis.The standard molar enthalpies of the solutions of SmCl3·6H2O(s),2[C7H6O3(s)],[C4H7NO2S(s)] and [Sm(C7H5O3)2·(C4H6NO2S)·2H2O(s)] in a mixed solvent of absolute ethyl alcohol,dimethyl formamide(DMF) and 3 mol/L HCl were,respectively,determined by calorimetry to be Δs Θ [SmCl3·6H2O(s),298.15 K]=(-46.68±0.15)...     

THIRD ORDER NONLINEAR OPTICAL PROPERTIES OF PERNIGRANILINE SOLUTION IN CONCENTRATED SULFURIC ACID

The fully oxidized state of polyaniline (PANI), pernigraniline (PN), was synthesizedby oxidation of the emeraldine base form of PANI dissolved in NMP solvent with m-chloroperoxybenzoic acid. The resulted PN was characterized by FTIR and UV-Visiblespectra. The third-order nonlinear optical properties of PN in concentrated sulfuric acid(PN/H_2SO_4) were measured by a degenerated four wave mixing (DFWM) method. The re-sults obtained suggest that the soliton-pair intermediate state associated with thedegenerated state does not play a major role in the third order nonlinear optical prop-erties of PANI.     

MULTIPHOTON EXCITATION OF A WATER MOLECULE IN INTENSE LASER FIELDS

A stretch vibration Hamiltonian of H_2O has been derived by using the second quantization, unitary transformations and the optimization of coefficients. The energy spectrum obtained from this Hamiltonian is in good agreement with that of experiments. The multiphoton excitation and the energy absorption of H_2O in intense laser fields have been calculated.     

THE CRYSTAL STRUCTURE OF THE ADDITION COMPOUND OF DECAVANADIC ACID AND 5,7-DIMETHYL-2, 3-DIHYDRO-1, 4-DIAZEPINIUM

The title compound crystallizes in the space group C_(2h)~5-P2_1/n with unit cell constantsa=10.938 A, b=19.189 A, c=13.384 A and β=105.09°. Intensities of 4022 independent reflec-tions were collected with four-circle diffractometer using MoKa radiation. After reduction fordiffractometer data, we derived first the position parameters of all the V atoms by directmethod using SHELXTL program. The coordinates of all the non-hydrogen and hydrogenatoms were obtained from successive Fourier and difference sytheses. The block-diagonalleast-squares refinement for all atoms gave a final discrepancy weighted factor R_w=0.050. The result of structure analysis shows that four protons of each decavanadic acid arecaptured by the nitrogen atoms involved in the azepine molecules which are condensation pro-ducts of ethylenediamine with acetylaceton. In crystal, the isopoly-decavanadate anion, 7-member heterocyclic azepium and the crystal water are linked together by ionic forces andhydrogen bonding and the chemical content within a unit cell has been identified as 2[H_2V_(10)O_(28)]~(-4)·8[C_7N_2H_(13)]~( 1)·12H_2O.     

Synthesis,Structure, and Magnetic and Luminescent Properties of Rare Earth Coordination Polymers Constructed from Mixed Dicarboxylates

Three unique metal-organic framework coordination polymers, [Eu_2(bptc)(bdc)_2(H_2O)]_n(1), [Gd_2(bptc)(bdc)_2(H_2O)_4]_n(2) and [Dy_2(bptc)(bdc)_2(H_2O)_4]n(3)(1,2-H_2 BDC = 1,2-benzenedicarboylic acid, H_2 bptc = 4,4?-biphenyldicarboxylic acid) were synthesized by mixing two different multi-carboxylic acids with Ln2 O3(Ln = Eu, Gd and Dy) in hydrothermal condition. The three compounds are all three-dimensional and compounds 2 and 3 contain 4.289 × 6.507 ?~2 rectangularshaped one-dimensional open channels along the a direction. Additionally, the magnetic, luminescent and thermogravimetric properties were studied in detail.     

The role of hydrogen-bonding interaction in poly(vinyl alcohol)/poly(acrylic acid) blending solutions and their films

<正>The aim of this work is to investigate the hydrogen-bonding interaction in poly(vinyl alcohol)(PVA)/poly(acrylic acid)(PAA) blending system and its influence on rheological properties in solution and the physical properties in solid state. Introducing PAA into PVA solutions resulted in a thickening behavior of blend solutions.The viscosity of the solutions increased with PAA content increasing,and a maximum viscosity could be obtained when the ratio of PVA/PAA was 70/30. The intermolecular hydrogen-bonding and miscibility between PVA and PAA in solid state were investigated by differential scanning calorimetry(DSC),Fourier transform infrared spectroscopy(FTIR) and mechanical measurements.The results displayed the great influence of introducing PAA on the properties of blending films.The tensile strength increased from 89.31 MPa to 119.8 MPa and Young's modulus improved by over 300%with increasing PAA concentration compared with those of pure PVA films.By systematically studying the rheological behaviors of solutions and the physical properties of films,the influence of hydrogen-bonding in solutions and solid states were discussed.     

Two New Coordination Polymers Based on H_4BIPA-TC: Syntheses and Fluorescence Sensing for Nitroaromatic Compounds and Fe~(3+) Ion

Based on the solvothermal reaction of 5,5'-(1,3,6,8-tetraoxobenzo[lmn][3,8] phenanthrolin-2-7-diyl)bis-1,3-benzenedicarboxylic acid(H_4L) linker and Zn(Ⅱ)/Cd(Ⅱ), two new 2 D coordination polymers(CPs), namely {[ZnH_2L(4,4'-bibp)]·H_2O}_n(1) and {[CdL_(0.5)(1,4-bimb)_(0.5)(H_2O)]·EtOH}n(2)(L = BIPA-TC), have been successfully constructed and characterized by EA, PXRD and IR with the aid of 4,4'-bis(benzoimidazo-1-yl)biphenyl(4,4'-bbib)/1,4-bis(imidazol-1-ylmethyl)benzene(1,4-bimb). The structural analysis showed that complex 1 exhibits a 3D supramolecular structure with the topology of sql, and complex 2 possesses a 2-nodal(4,6)-c framework with the topology of(3~2·4~2·5~2)(3~4·4~4·5~4·6~3)-4,6 T26. Fluorescent experiments showed that 1 and 2 have high selectivity and sensitivity for the sensing of nitroaromatic compounds and Fe~(3+) in aqueous solutions.     

Effect of synthesis solution pH of Co/γ-Al_2O_3 catalyst on its catalytic properties for methane conversion to syngas

The cobalt nanoparticles over γ-Al_2O_3 support were prepared via chemical reduction of CoCl_2·6H_2O using NaBH_4 with various values of pH in the range of 11. 92-13. 80. Synthesized catalysts were studied through X-ray diffraction( XRD),N_2 adsorption/desorption( BET),H_2-temperature programmed reduction( H_2-TPR),H_2-chemisorption,O_2 pulse titration and temperature programmed oxidation( TPO) methods. Obtained results exhibited the synthesis solution pH showed a significant influence on the activity and selectivity in partial oxidation of methane reaction. The methane conversion,CO selectivity and H_2 yield were enhanced by increasing of the synthesis solution pH. Compared to other catalysts,the catalyst that synthesized at pH of 13.80,showed a superior ability in syngas production with a H_2/CO ratio of near 2 and also a proper stability against deactivation during the partial oxidation of methane.     

Synthesis and Structure of a New Gadolinium Porous Complex Assembled from 2,3-Pyrazinedicarboxylic Acid and Ammonia

A new gadolinium porous complex,(NH_4)_2[Gd2(pzdc)4(H_2O)2], was synthesized through hydrothermal reaction of 2,3-pyrazinedicarboxylic acid and Gd(NO3)3·6 H_2O with the pH value adjusted by ammonia. It was characterized by elemental analysis, FT-IR, TGA and further by single-crystal X-ray crystallography. It crystallizes in monoclinic, space group P21/c with a = 14.249(7), b = 15.889(8), c = 12.846(7) ?, β = 95.724(10)°, V = 2894(3) ?3, Z = 4, Dc = 2.385 g/cm3, μ(Mo Ka) = 4.65 mm–1 and F(000) = 1976. 1976 reflections were measured and 6446 independent reflections(Rint = 0.0985) were used in further refinement. The complex exhibits a 3D framework constructed from the [Gd2(pzdc)4(H_2O)2]2-building blocks. It is scarce that the NH4+ cations are located in the channels and balance the charge of anion framework. Furthermore, the ion exchange property of this complex has also been studied. The NH4+ cations can be replaced by Na+ cations, which is an uncommon phenomenon for gadolinium-containing porous complex.     

STUDIES ON ORGANOMETALLIC COMPOUNDS OF TITANIUM,ZIRCONIUM AND HAFNIUM——THE SYNTHESES AND PROPERTIES OF BIS (CYCLOPENTADIENYL) AND BIS (METHYLCYCLOPENTADIENYL) DI(ARYL)-METAL DERIVATIVES

Aryllithium reacts with Cp_2MCl_2 and Cp'_2 MCl_2 (C_p=η~5-C_5H_5, C_P′=η~5-CH_3C_5H_4:M=Ti, Zr, Hf) respectively to prepare a series of new bis (cyclopentadienyl), bis (methy-lcyclopentadienyl) diaryl derivatives of titanium, zirconium and hafnium. The hydrolysicreaction of these organometallic compounds are studied, the derivatives of zirconium andhafnium can be easily hydrolyzed with the exception of that of titanium. They react withhydrogen chloride, acetyl chloride, bromine and haloacids to form the respective bis(cyclo-pentadionyl) dihalides of these metals. The NMR and IR spectra were discussed in regardto the structure of (η~5--CH_3C_5H_4)_2 MAr_2 and (η~5--CH_3C_5H_4)_2 MX_2.