Search

Abstract: In this paper, the structure of 1-carboxymethyl-3-methylimidazolium chloride was studied by X-ray diffraction, density functional theory, and FT–IR and Raman spectroscopic techniques for the first time. Title compound crystallizes in the orthorhombic space group Pca2 1 with the cell dimensions a =13.445 (6)Å, b =6.382 (3)Å, c =9.727 (5)Å and V =834.6 (7)Å3. All the geometrical parameters have been calculated using by B3LYP with 6–311G++(d,p) basis set. Optimized geometries have been compared with the experimental data, and the hydrogen bond and short contact interactions were discussed. The vibrational frequencies, infrared intensities and Raman scattering activities of the title compound were calculated at the same level. The observed bands were assigned based on the theoretical calculations. The scaled vibrational frequencies seem to coincide with the experimental data with acceptable deviations. [Copyright &y& Elsevier]

Abstract: The infrared (4000–400cm−1) and Raman spectra (3700–100cm−1) of liquid S-phenyl thioacetate have been recorded. Molecular geometry, vibrational frequencies and the corresponding assignments were performed by density funtional theory (DFT) using the 6-311++G(d,p) basis set. Two conformers have been identified. One is syn form where the carbonyl group is on the same side of the phenyl ring and the other is the anti form. The energy difference between these two configurations is about 1.63kcalmol−1 at B3LYP/6-311++G(d,p) level. By utilizing the more stable syn conformer, a complete assignment of the observed frequencies is given according to the total energy distribution of the vibrational modes. The general agreements between the observed and the calculated frequencies are shown. [Copyright &y& Elsevier]

Abstract: In this paper, experimental and theoretical studies on the molecular structure and vibrational spectra of methyl 2,5-dichlorobenzoate (MDCB) are presented. Fourier transform infrared and Raman spectra of the title molecule in the solid phase were recorded and analyzed. The geometrical parameters were calculated using DFT (B3LYP) with 6-311G(d,p) and 6-311++G(d,p) basis sets, and compared with the experimental data. The vibrational frequencies, infrared intensities and Raman scattering activities were also reported. The detailed assignments were given based on the total energy distribution of the vibrational modes, calculated with scaled quantum mechanics method. The observed and calculated frequencies are found to be in good agreement. [Copyright &y& Elsevier]

Abstract: Molecular structure and vibrational spectra of 1,4-dihydroxyanthraquinone (1,4-DAQ) are studied theoretically and experimentally. FT-infrared and Raman spectra of 1,4-DAQ are recorded in solid phase in regions of 4000–400 and 3500–100cm−1, respectively. The geometry of 1,4-DAQ is optimized by B3LYP and B3PW91 methods, and the most stable structure with C2v point group is found. The harmonic vibration frequencies, infrared intensities, and the Raman scattering activities of the compound are calculated, analyzed, and compared with experimental data. Our calculated frequencies agree well with the experimental results. [Copyright &y& Elsevier]

Abstract: In order to deepen the understanding of the cation–anion interaction in ionic liquids, the structures of cation, anions, and cation–anion ion-pairs of 1-allyl-3-methylimidazolium-based ionic liquids are optimized using density functional theory (DFT), and their most stable geometries are discussed. The structural parameters, hydrogen bonds and interaction energies of 1-allyl-3-methylimidazolium dicyanamide ([Amim]DCA), 1-allyl-3-methylimidazolium chloride ([Amim]Cl), 1-allyl-3-methylimidazolium formate ([Amim]FmO) and 1-allyl-3-methylimidazolium acetate ([Amim]AcO) ion pairs are studied. The vibrational frequencies of [Amim]DCA and [Amim]Cl have been calculated and scaled values have been compared with experimental FT-IR and FT-Raman spectra. The complete assignments were performed on the basis of the potential energy distribution (PED) of the vibrational modes. [Copyright &y& Elsevier]

Highlights: [•] The FT-IR and FT-Raman spectra of N4-acetylcytosine were recorded and analyzed. [•] Different conformers of N4-acetylcytosine have been given. [•] The complete vibrational assignments and spectroscopic analysis were made. [ABSTRACT FROM AUTHOR]

The zinc (II) complex with nicotinamide, (C 6 H 11 N 2 )[ZnBr 3 (C 6 H 6 N 2 O)], was prepared under ionothermal condition by using the ionic liquid 1-ethyl-3-methylimidazolium bromide ([EMIM]Br) as a solvent. At the same time, [EMIM]Br also functions as a structure-directing agent, leading to a framework structure different from those obtained by the conventional methods. Single-crystal X-ray analysis revealed that the coordinated compound crystallizes in monoclinic space group P 2(1)/ c , and the Zn (II) ion is four-coordinated by one pyridine ring N atom and three bromide anions in a slightly distorted tetrahedron arrangement. The [EMIM] + cations acting as the extra framework charge balancing species occupy the channels of this asymmetric unit. In the crystal structure, intermolecular N H⋯Br and N H⋯O hydrogen bonds link the molecules to form a supramolecular structure. In addition, this compound was further characterized by FT-IR and Raman spectroscopic techniques, and the observed important bands were assigned. Thermogravimetric analysis (TG), Differential Scanning Calorimetry (DSC) and fluorescent properties of solid samples were also studied at room temperature. [ABSTRACT FROM AUTHOR]

Abstract: As an effective extraction method, aqueous two-phase extraction systems based on imidazolium ionic liquids have been used, in this work, to extract proteins of bovine serum albumin, trypsin, cytochrome c and γ-globulins. Effects of the ionic liquids concentration, pH value, and temperature of the systems on the extraction efficiencies have been investigated. Experimental results show that 75–100% of the proteins could be extracted into the ionic liquid-rich phase in a single-step extraction. The extraction efficiency of cytochrome c was changed slightly with the increase of pH values. Extraction efficiencies of the proteins were found to increase with increasing temperature and increasing alkyl chain length of cation of the ionic liquids. Thermodynamic studies indicated that hydrophobic interactions were the main driving force, although electrostatic interactions and salting-out effects were also important for the transfer of the proteins. Importantly, conformation of the proteins was not affected after extraction into the upper ionic liquid-rich phase as determined by UV–visible (UV–vis) and Fourier transform infrared (FT-IR) spectroscopy of the proteins. The enzyme activity of native trypsin and the trypsin in ionic liquids was determined using N-α-benzoyl-l-arginine ethyl ester as a substrate. This novel process is suggested to have important applications for the separation of proteins. [Copyright &y& Elsevier]