Solute-solvent interactions in formamide and zinc chloride solutions: An investigation by Raman spectroscopy

Raman experiments of formamide and zinc chloride solutions in a wide concentration range (0.1-5.0 mol kg⁻¹) have been carried out. The spectral changes were interpreted on three different ways: (i) the rupture of the H-bonds of FA was evidenced by the trend observed in the ν_CO, δ_HNH and restricted (translation or libration) modes; (ii) the appearance of a new band in the ν_CN region (∼1338 cm⁻¹) was assigned to FA coordinated to Zn (II) through nitrogen atom; (iii) the electronic delocalization in the FA structure upon complexation provided the appearance of new features in the δ_CH and ν_CH regions. The quantitative treatment performed at the ν_CN region of FA allowed the determination of an average number of 3 FA molecules per Zn (II) in the first solvation shell. This value is supported by the appearance of features assigned to ZnCl⁺ and ZnCl₂ entities that also occupy vertices of the tetrahedron at higher salt concentrations. The present study may be useful for a better understanding on electrochemical processes employed in the production of dendritic zinc films as well as FA hydrolysis catalyzed by this metal.     

Comment on the assignments of some vibrational bands of oxalyl fluoride

In view of existing contradictory assignments of the symmetrical stretching vibrations associated with the formal C-C and C-F bonds of trans/cis oxalyl fluoride, an additional theoretical analysis of the corresponding calculated wavenumbers was preformed on trans-C₂O₂F₂ and cis-C₂O₂F₂ based on previously calculated ab initio scaled force fields at the HF/6-31G computational level and new force fields calculated at the MP2/aug-cc-pVTZ level. This novel analysis included computational data from the isotopic shifts brought about by incorporating ¹³C and ¹⁴C atoms into the structure. A detailed examination of the calculated wavenumbers made it possible to validate the assignments of the ν₂ and ν₃ wavenumbers in the trans-C₂O₂F₂ and cis-C₂O₂F₂ molecules as the formal C-C bond stretching and the formal C-F bond symmetrical stretching vibrations, respectively.     

A novel biological strategy for morphology control of PbWO4 crystals in tomato extract

PbWO(4) crystals were readily synthesized by reacting lead oxide (PbO(2)) with sodium tungstate (Na(2)WO(4)·2H(2)O) at room temperature in the presence of tomato extract. Biomolecules such as vitamins, proteins in the extract played both the roles of reductant and template. The size and morphology of the PbWO(4) crystals could be controlled by adjusting the concentration of the reactants. When the concentration ratio of PbO(2) and Na(2)WO(4) was increased, the morphologies of the products varied from spherical to fusiform. Room-temperature fluorescence spectra indicated the products had a slight blue shift compared to the solid structure, which may be due to the structure defects in the crystals. The possible mechanism of PbWO(4) crystal growth in tomato extract was discussed.     

Novel tricarbonyl rhenium complexes of 5,8-quinolinedione derivatives - Synthesis, spectroscopic characterisation, X-ray structure and DFT calculations

The molecular structure of 7-acetamido-2-methyl-quinoline-5,8-dione has been determined and the reactivity of 7-acetamido-2-methyl-quinoline-5,8-dione (1) and 6-acetamido-2-methyl-quinoline-5,8-dione (2) towards Re(CO)₅Cl has been examined. Two novel tricarbonyl rhenium complexes, fac-[Re(CO)₃(7-acetamido-2-methyl-quinoline-5,8-dione)Cl]·CHCl₃ (3·CHCl₃) and fac-[Re(CO)₃(6-acetamido-2-methyl-quinoline-5,8-dione)Cl]₂·CHCl₃ (4·CHCl₃), have been synthesized and characterized spectroscopically and structurally. The electronic spectrum of 3 was investigated at the TDDFT level employing B3LYP functional in combination with LANL2DZ.     

Syntheses,Crystal Structures and Property Studies on Cu（Ⅱ） and Co（Ⅱ） Complexes with 1,8-Naphthalimid Schiff Base

The ligand of N-(2-hydroxybenzylideneamino)-1,8-naphthalimide (HL) and its metal complexes of CuL2 (1) and CoL2 (2) have been synthesized. Elemental analysis, IR and X-ray single-crystal diffraction characterizations for 1 and 2 have been carried out. In the complexes of 1 and 2, the central metallic ions of Cu2+ and Co2+ coordinate with two deprotonated ligands of L-, respectively and adopt distorted square planar geometries. The thermal analysis result shows that the two complexes undergo two similar decomposition processes because of their similar geometric configurations. For the two complexes, fluorescence spectra measurements indicate that complex CoL2 emits stronger blue fluorescence than HL and the complex CuL2 does not emit fluorescence at all.     

Glass transition of hydrated wheat gliadin powders

Modulated-temperature differential scanning calorimetric and dynamic mechanical analyses and dielectric spectroscopy were used to investigate the glass transition of hydrated wheat gliadin powders with moisture absorption ranged from 2.30 db%to 18.21 db%.Glass transition temperature(I_g)of dry wheat gliadin was estimated according to the Gordon Taylor equation.Structural heterogeneity at high degrees of hydration was revealed in dielectric temperature and frequency spectra.The activation energies(E_a)of the two relaxations were calculated from Arrhenius equation.     

Cyclopalladated Ferrocenylimine Catalyzed Chlorination of 2‐Arylbenzoxazoles

An efficient and facile protocol for palladacycle‐catalyzed chlorination of 2‐arylbenzoxazoles was developed. The results represent the first examples involving the palladacycle as the catalyst for such chlorination. This chlorination was not a ligand‐directed ortho‐C H activation, but an electrophilic substitution process at the para‐position of the nitrogen atom in the benzo ring of benzoxazole moiety, the regiochemistry of which had been confirmed by HMBC spectral analysis. The catalytic system could tolerate various halogen atoms, such as F, Cl and Br, affording the corresponding products in moderate to excellent yields.     

Crystal structure and DNA binding studies of a cobalt(Ⅱ) complex containing mixed-ligands of 1,10-phenathroline and glycollic acid

A cobalt（11） complex containing mixed-ligands of 1,10-phenathroline（phen） and glycollic acid（GA）.|Co（GA）₂（phen）| was synthesized and its structure was characterized by X-ray diffraction.The interaction of the complex with DNA was investigated by electronic absorption spectra and electrochemical methods.Electronic absorption spectrum experiments showed that after interaction with DNA.the characteristic absorption peaks of |Co（GA）₂（phen）| underwent hypochromic effect as well as redshift. Also,the binding strength of 3.8×10⁴L/mol was estimated by titration method.Electrochemical assays revealed that the redox peak currents of the complex decreased obviously accompanied by a positive shift of the formal potential after association with DNA.All these results revealed that the synthesized cobalt complex bound with DNA via an intercalation mode.     

Dual Spectroscopic Responses of Pyridinium Hemicyanine Dyes to Anions

The absorption and fluorescence spectroscopic responses of three pyridinium hemicyanine dyes to anions F⁻, Cl⁻, Br⁻, I⁻, H₂PO₄⁻, HSO₄⁻ and OAc⁻ were investigated. At lower concentrations of OAc⁻ (less than 1 equiv.), both the absorption and the fluorescence intensities of 1 – 3 were more effectively changed than F⁻ at identical concentrations. At higher concentrations of OAc⁻ (more than 1 equiv.), the interaction was opposite for each compound. ¹H NMR results indicated the interaction between 1 , 2 or 3 and F⁻ proceeded through hydrogen bonding. The results showed that these dyes are promising to develop dual fluorescence and chromogenic chemosensors toward F⁻ and OAc⁻ according to the subtle difference in the affinity of F⁻ and OAc⁻.     

水溶性七甲川吲哚菁染料的合成及其在含CTAB溶液中的光谱研究

本文合成并表征了一种水溶性七甲川吲哚菁染料,测试了染料在不同溶剂和不同浓度的表面活性剂十六烷基三甲基溴化铵(CTAB)中的吸收和荧光光谱性质.结果表明:染料的最大吸收和荧光发射光谱值(乙醇中)分别是796nm和813nm.随着溶剂的黏度增大,染料的荧光强度逐渐减弱.CTAB形成胶束前,随着CTAB浓度的增大,染料的吸收...