Study of molecular structure and vibrational spectra of poly (β,-l-malic acid) [PMLA] using DFT approach

Poly (β-L-malic acid) (PMLA) is a biodegradable polymer and it has various important applications in the biomedical field. In the present work the structural and spectral characteristics of PMLA have been studied by methods of infrared, Raman spectroscopy and quantum chemistry. Electrostatic potential surface, optimized geometry, harmonic vibrational frequencies, infrared intensities and activities of Raman scattering were calculated by density functional theory (DFT) using oligomeric approach employing B3LYP with complete relaxation in the potential energy surface using 6-311++G (d, p) basis set. Based on results, we have discussed the correlation between the vibrational modes and the structure of the PMLA. A complete analysis of the experimental infrared and Raman spectra has been reported on the basis of wavenumber of the vibrational bands and potential energy distribution. The calculated HOMO and LUMO energies shows that charge transfer occur within the molecule. The calculated infrared and the Raman spectra of the polymer based on DFT calculations show reasonable agreement with the experimental results.     

Effects of molecular weight on poly(ω-pentadecalactone) mechanical and thermal properties

A series of poly(ω-pentadecalactone) (PPDL) samples, synthesized by lipase catalysis, were prepared by systematic variation of reaction time and water content. These samples possessed weight-average molecular weights (M_w), determined by multi-angle laser light scattering (MALLS), from 2.5 × 10⁴ to 48.1 × 10⁴. Cold-drawing tensile tests at room temperature of PPDL samples with M_w between 4.5 × 10⁴ and 8.1 × 10⁴ showed a brittle-to-ductile transition. For PPDL with M_w of 8.1 × 10⁴, inter-fibrillar slippage dominates during deformation until fracture. Increasing M_w above 18.9 × 10⁴ resulted in enhanced entanglement network strength and strain-hardening. The high M_w samples also exhibited tough properties with elongation at break about 650% and tensile strength about 60.8 MPa, comparable to linear high density polyethylene (HDPE). Relationships among molecular weight, Young's modulus, stress, strain at yield, melting and crystallization enthalpy (by differential scanning calorimetry, DSC) and crystallinity (from wide-angle X-ray diffraction, WAXD) were correlated for PPDL samples. Similarities and differences of linear HDPE and PPDL molecular weight dependence on their mechanical and thermal properties were also compared.     

A Ladder-like Coordination Polymer [Sr(H2O)4(CuL)2]·(CuL)·2.25H2O Constructed From Metallo-Ligand Na[CuL] and Sr(NO3)2: Crystal Structure and ESR Study

Ligand L (H₃L = Glycylglycine, N-[1-(2-hydroxy,5-bromophenyl)propylidene]) has been prepared which contain flexible dipeptide group and substituted phenol group. The ligand react with Cu(NO₃)₂ to give the metallo-ligand [CuL]⁻, in which L acting as quadridentate ONNO chelate, coordinate to Cu(II) ion. The metallo-ligand [CuL]⁻ is rigid and has multifunctional groups. Reaction of metallo-ligand with Sr(NO₃)₂ leads to the formation of the title complexes [Sr(H₂O)₄(CuL)₂]· (CuL)·2.25H₂O (1). This heteronuclear compound has been characterized by elemental analyses, spectroscopic analyses, and single crystal diffraction. Structural analyses reveal that the complex was crystallized in triclinic space group P-1 and has intricate 2D net-structure, which contain an infinite 1D [Sr(H₂O)₄(CuL)₂]⁺ ladder-like structure. In addition ESR (electron spin resonance) property and thermogravimetric analysis of 1 are discussed in detail.     

Synthesis and Characterization of the Luminescent Poly[2-decyloxy-5-(2′,5′-bis(decyloxy)phenyl)-1,4-phenylenevinylene]

A new soluble luminescent poly[2-decyloxy-5-(2′,5′-bis(decyloxy)phenyl)-1,4-phenylenevinylene] (DBDP-PPV) is prepared by the dehydrohalogenation of 1,4-bis(bromomethyl)-2-decyloxy-5-(2′,5′-bis(decyloxy)phenyl) benzene (as monomer) in this study. The above monomer bearing decyloxy and 2′,5′-bis(decyloxy)phenyl substituents was prepared via such chemical reactions as alkylation, bromination, and Suzuki coupling reactions. The two asymmetric substituents on the phenylene ring make the DBDP-PPV soluble in organic solvents and eliminate the tolan-bis-benzyl (TBB) structure defects. The structure and properties of the DBDP-PPV are examined by ¹H-NMR, FT-IR, UV/Vis, TGA, photoluminescence (PL), and electroluminescence (EL) analyses. The DBDP-PPV film exhibits a PL peak at 519 nm. With the DBDP-PPV acting as a light-emitting polymer, a device is fabricated with a sequential lamination of ITO/PEDOT/DBDP-PPV/Ca/Ag. The EL spectrum of the device shows a maximum emission at 507 nm. The turn on voltage of the device is about 15.6 V. Its maximum brightness is 4.67 cd/m² at a voltage of 16.8 V.     

Crystal Structure and Magnetic Properties of a Novel Helical Coordination Polymer [Cu2(pda)2(phen)2(H2O)2]·6H2O

A novel coordination polymer of Cu^II with flexible ligands, namely, [Cu ₂ (pda) ₂ (phen) ₂ (H ₂ O) ₂ ]·6H ₂ O (1) (H₂pda = 1,3-phenylenediacetic acid, phen = 1,10-phenanthroline), was synthesized by hydrothermal reactions and characterized by single-crystal X-ray diffraction, thermogravimetric analyses, elemental analysis and IR spectroscopy. In complex 1, the Cu^II ions are linked by pda ligands to form 1D helical chains. The adjacent chains are related by the π–π stacking interactions and exhibit opposite chirality, which result in extended 2D heterochiral helical-layers. Furthermore, the 2D helical-layers are assembled into 3D supramolecular edifices through heterochiral helical hydrogen bonding. In addition, the thermal stability and magnetic properties of 1 are reported.     

2-羟基-4-氧杂三环[4,2,1,03,7]-5-壬酮的合成与表征

2-羟基-4-氧杂三环[4,2,1,03,7]-5-壬酮是光电材料的重要中间体,本文以丙烯酸和环戊二烯为原料,经Diels-Alder和氧化合成目标化合物,并通过1H NMR、13C NMR、MS和IR表征确定了5-降冰片烯-2-甲酸和目标化合物结构。     

Palladium(II) complexes with Pd2S2 rings. Synthesis and theoretical characterization of [Pd2(dppe)2(μ-S)2] and X-ray characterization of [Pd3(dppe)3(μ3-S)2]Cl2

The use of the dppe ligand and the fine tuning of the experimental conditions has allowed isolation of [Pd₂(dppe)₂)(μ-S)₂], whose structural characterization has been achieved by ab initio MP2 calculations, and of [Pd₃(dppe)₃(μ₃-S)₂]Cl₂, the X-ray structure of which is also reported.     

Synthesis of poly(α-thiophenediyl)benzylidene with high molecular weight and its thermal stability

Summary The synthesis of poly(-thiophenediyl)benzylidene (PTB) with high molecular weight is described. Number-average degrees of polymerization reached about 74. The characterizations of the polymer was investigated by ¹H-NMR, ¹³C-NMR, IR, and UV-VIS spectra. The polymer with well-defined structure and high molecular weight was obtained by polymerization at low temperature and in polar solvent. This polymer was thermally stable and a thermal decomposition took place at 391°C under nitrogen and at 370°C under air. The glass transformation temperature was 117°C and this PTB was nonfusible.     

A new polymeric chain in the dihydrogendecavanadate(V)–decavanadate(V) [NH2(CH2)4]5[V10O28H2]0.5[V10O28]0.5 obtained by in situ synthesis of the organic cation

A new polymeric compound, [NH₂(CH₂)₄]₅[V₁₀O₂₈H₂]_0.5[V₁₀O₂₈]_0.5, was obtained by in situ synthesis of the organic cation from an aqueous solution of V₂O₅–HCl–NH₂(CH₂)₄NH₂. The crystal structure was solved by single-crystal X-ray diffraction. [NH₂(CH₂)₄]₅[V₁₀O₂₈H₂]_0.5[V₁₀O₂₈]_0.5 consists of dihydrogendecavanadate(V), [H₂V₁₀O₂₈]^4?, and decavanadate(V), [V₁₀O₂₈]^6?, units assembled in one-dimensional arrays by interanionic hydrogen bonds O–H?O and cation-anion N–H?O interactions. The latter involve pyrrolidinium cations, which were obtained in the compound instead of the starting butane-1,4-diamine. Pyrrolidinium cations further connect the polymeric chains into a three-dimensional network. The presence of the two types of units, [H_nV₁₀O₂₈]^(6?n)? with n = 0 and n = 2, in one compound was not yet observed and is herein reported for the first time.     

Efficient conversion of monosaccharides into 5-hydroxymethylfurfural and levulinic acid in InCl3–H2O medium

The conversion of fructose into 5-hydroxymethylfurfural (5-HMF) and levulinic acid (LA) was investigated and catalyzed by indium trichloride (InCl₃) in water. 79% 5-HMF yield (15 min) and 45% LA yield (60 min) were obtained at 180 °C with 2.5 mol% InCl₃. Additionally, comparative studies of glucose/fructose mixture with different ratios as substrates were carried out to manifest the isomerization process between glucose and fructose during the conversion of monosaccharides into chemicals. It was shown that InCl₃ was not only active in the isomerization of glucose to fructose and the reverse direction, but also demonstrated an excellent activity in the dehydration and conversion of monosaccharides. InCl₃–H₂O system presented a remarkable catalytic effect on the dehydration and conversion of monosaccharides.     

Novel hetero-polynuclear metal complexes (CuL)3[Mn(NCS)5]2 and (NiL)3[Mn(NCS)5]2 containing trigonal bipyramidal geometric [Mn(NCS)5]3− as bridging ligand

Two thiocyanate-bridged hetero-pentanuclear complexes (CuL)₃[Mn(NCS)₅]₂ (1) and (NiL)₃[Mn(NCS)₅]₂ (2) have been successfully synthesized and characterized by X-ray single crystal diffraction, elemental analysis, IR, TGA and magnetic measurements. (L = N-dl-5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene). Single crystal structure analysis indicates that complex 1 and 2 have similar structures in which the Mn(II) atom is five-coordinated in a trigonal bipyramidal geometry by five N atoms from five thiocyanate ligands. The Cu(II) and Ni(II) both show two different coordination environments, square pyramidal and distorted octahedron. Three Cu(II) (or Ni(II)) ions and two Mn(II) ions are bridged by the end-to-end thiocyanate ligands to form pentanuclear entities. The pentanuclear entities are further linked to 3D framework by the hydrogen bonds. The variable-temperature magnetic measurements for 1 indicated weak antiferromagnetic interaction between the Cu(II) and Mn(II) ions.     

Synthesis and properties of poly[2-(4′-oxyphenylene)-5-benzimidazole] and a proton-exchange membrane produced on its basis

A monomer of the A-B type, 3,4-diamino-4′-carboxydiphenyloxide, has been synthesized via a series of consecutive transformations of 5-chloro-2-nitroaniline. The homopolycondensation of the monomer in Eaton’s reagent at 140°C yields poly[2-(4′-oxyphenylene)-5-benzimidazole] soluble in organic solvents. A membrane containing 51% H₃PO₄ (2.9 acid molecules pert monomer unit) and possessing a proton conductivity of 0.025 S/cm at 160°C is produced by doping a polymer film with 60% H₃PO₄.     

Structure characterization and thermophysical properties of R2LaTaO7 (R = Dy and Y) oxides

In the present work, the structure and thermophysical performances of Dy₂LaTaO₇ and Y₂LaTaO₇ were investigated. Analytical results show that Dy₂LaTaO₇ and Y₂LaTaO₇ exhibit single orthorhombic weberite structure. Because of the strong phonon scattering resulted by complicated structure, oxygen vacancies and doped atoms, their thermal conductivities are lower than value of Y₂O₃ stabilized ZrO₂. The obtained compounds show that eminent phase stability is up to 1473?K. The heat expansion quotietis are also lower than value of Y₂O₃ stabilized ZrO₂, and the lowest heat expansion quotiety of Y₂LaTaO₇ may be ascribed to the low ion size of Y³⁺ ions.     

Structure of a catalytically active octanuclear cobalt complex [Co(II)4Co(III)4(μ4-O)4(μ-O2CPh)12(PhCOOH)4]

The structure of a catalytically active octanuclear mixed-valence cobalt complex [Co(II)₄Co(III)₄(μ₄-O)₄(μ-O₂CPh)₁₂(PhCOOH)₄] (Ph = phenyl, C₆H₅) has been determined using an X-ray diffraction analysis. The presence of 16 ligands containing phenyl rings in each complex gives rise to strong steric stresses and leads to a disordering of terminal groups. The compound crystallizes in the monoclinic crystal system, space group of symmetry P2₁/n, with the unit cell parameters a = 18.076(5) ?, b = 26.371(3) ?, c = 22.791(5) ? β = 92.48(1)°, V = 10853(4) ?³, Z = 4, and ρ = 1.516 g/cm³. The final values of the discrepancy factors are R1 = 0.0441 for 4005 symmetrically nonequivalent reflections with I ≥ 2σ(I), wR2 = 0.1131, and GooF = 0.943.     

Hydrothermal Synthesis and Crystal Structures of Cd(II)-Based 1D Coordination Polymer and Mn(II) Coordination Complex with Mixed N- and O-donor Ligands: [Cd2(4-4′-bpy)2(pa)4]n·0.25(H2O) and [Mn(4-4′-bpy)2(pa)(H2O)3]ClO4·2(H2O)

Two new complexes, [Cd₂(4-4′-bpy)₂(pa)₄] _n ·0.25H₂O (1) (pa = phenylacetate), and [Mn(4-4′-bpy)₂(pa)(H₂O)₃]ClO₄·2H₂O, (2), have been obtained from hydrothermal reaction of Cd(NO₃)₂·4H₂O and Mn(ClO₄)₂·6H₂O with a mixture of the ligands, 2-phenylmalonic acid (2-phmalH₂) and 4-4′-bipyridine (4-4′-bpy). The pa is formed in situ by decarboxylation of phenylmalonic acid. These complexes have been characterized by elemental analysis, FT-IR spectroscopy, thermogravimetric analysis and single-crystal X-Ray diffraction. The Cd(II) center is seven-coordinate and linked via pa ligands to form a binuclear complex in the asymmetric unit of 1. A ladder-like 1D chain of binuclear units is formed by Cd(II)–N coordination bond through 4-4′-bpy ligands. Complex 2 consists of a mononuclear manganese center based on a distorted octahedral geometry and exhibits a supramolecular structure containing hydrogen bonds and extensive π···π and C–H···π interactions.     

Extraction and recovery of cadmium(Ⅱ) using phosphine-oxide,tris[(dibutylamino)methyl]-(7CI,8CI) from nitric acid solutions

In the present article, a new separation system was employed for the extraction of cadmium from nitric acid solutions for the first time. Phosphine oxide, tris[(dibutylamino)methyl]-(7CI,8CI),which contains nitrogen atoms and phosphorus atom in molecular, was used as extractant. The influence of the following parameters was investigated: the organic/aqueous phase ratio (O/A), pH, contact time, temperature, the concentration of extractant, cadmium (Ⅱ), sodium nitrate and sodium chloride. Results demonstrated that quantitative extraction of cadmium was feasible from 50 mg/L cadmium feed solution in a single stage at pH 3.0, 15 min and O/A phase ratio 1:5 with 20% extractant in cyclohexane diluent. The cadmium extraction isotherm under different cadmium ion concentrations was established. The loaded cadmium could be stripped by 4 mol/L ammonium chloride aqueous solutions. A contrast study was carried out, and the results indicated that phosphine oxide, tris[(dibutylamino)methyl] –(7CI,8CI), could take the place of commercial organo-phosphorous extractants in the process of cadmium(II) extractions for its effectivity, stability and low price.     

Synthesis and evaluation of different adsorbents based on poly(methacrylic acid–trimethylolpropane trimethacrylate) and poly(vinylimidazole–trimethylolpropane trimethacrylate) for the adsorption of tebuthiuron from aqueous medium

In the present study a new cross-linked copolymer poly(methacrylic acid–trimethylolpropane trimethacrylate) (named PMA) and poly(vinylimidazole–trimethylolpropane trimethacrylate) (named PVI) was synthesized through precipitation polymerization and applied to the adsorption of tebuthiuron. Adsorbent materials were characterized by using FT-IR, SEM, TGA, textural data, and elemental analysis. Kinetic study showed that the tebuthiuron adsorption was very quick and the equilibrium time was achieved at 20 min for both polymers. Experimental kinetic data for both polymers were very well described by the second-order kinetic model, thus indicating that tebuthiuron adsorption involves chemical adsorption in different binding sites, which could control the reaction rate. Adsorption equilibrium data were better fitted to the dual-site Langmuir–Freundlich model, which recognizes the existence of two kinds of adsorption sites on the polymer surface ascribed to the presence of carboxyl and carbonyl groups from PMA and imidazole ring and carbonyl group from PVI. The maximum adsorption capacities of PMA and PVI were found to be 186.76 and 213.89 mg g^− 1, respectively, which are much higher than other adsorbents.