Enhanced Photocatalytic Activity of TiO2 Modified with GaI toward Environmental Application.

Gallium (Ga) ion-doped TiO2 (Ga-TiO2) nanocomposite with small particle size (9-10 nm) and high surface area (104 m2/g) has been easily synthesized via sol-gel method at low temperature by using low-valent GaI as a doping precursor. The structural and morphological characterization of Ga-TiO2 was carried out with standard analytical and spectroscopic techniques. Ga doping into the TiO2 matrix inhibited a phase transformation from anatase to rutile (photocatalytically inactive) form, even at a higher temperature of 750 °C. Finally, Ga-TiO2 nanocomposite showed high photocatalytic activity and exhibited 97% degradation of acid violet 63 dye within 60 min. The dye degradation rate constant was calculated as 1.6 × 10-1 and 1.4 × 10-1 min-1 under UV and white light irradiation, respectively, which is higher, as compared to the previously reported Ga-TiO2 composites to date.

A novel coordination mode of κ1-N-Br-pyridylbenz-(imida, oxa or othia)-zole to Pt(ii): synthesis, characterization, electrochemical and structural analysis.

Herein, three novel Pt(ii) complexes with formula [trans-Pt(Br-PyBenz-X)(Cl)2(DMSO)] (1-3) having Br-pyridylbenz-(imida, oxa or othia)-zole (L1-3) derivatives as potential bidentate ligands, under an unusual κ1-N-coordination mode are reported. All compounds were obtained straightforwardly via reaction of corresponding LPB1-3 and [Pt(Cl)2(DMSO)2] (DMSO = dimethyl sulfoxide), at 100 °C in acetonitrile, respectively. 1-3 complexes were characterized by analytical and spectroscopic data: melting point, FT-IR, Raman, UV/Vis and NMR experiments. Cyclic voltammetry studies show an irreversible two-electron process at -0.50 and -0.51 V, which was ascribed to the Pt(ii)/Pt(iv) couple, for complexes 2 and 3. The crystal structure of complex 2 was elucidated by single-crystal X-ray diffraction, where the platinum atom exhibits a square plane geometry, where LPB2 adopts an unusual mono-coordinated mode via an N-κ1-benzoxazole ring. According to DFT calculations the first N-coordination exchanging one DMSO molecule is favourable, while the second N-coordination is highly impeded.

Determination of copper and lead in tequila by conventional matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and partial least squares regression.

RATIONALE: Quantification of small molecules by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) is challenging yet attractive, due to micro-scale procedural simplicity, high throughput and lack of memory effects. Since these features are important while analyzing trace elements in quality control schemes, MALDI-TOFMS was used for the determination of copper (Cu) and lead (Pb) in tequila with quantification carried out by partial least squares regression (PLS2) and by univariate calibration (UC). METHODS: In the proposed procedure, Bi(III) was added as internal standard (IS), diethyldithiocarbamate complexes were formed (pH 7.4) and extracted into chloroform; after solvent evaporation and re-constitution in acetonitrile, the sample was co-crystallized with α-cyano-4-hydroxycinnamic acid on a steel target. From the acquired mass spectra, UC was performed using IS-normalized signals of the monoisotopic ions of analytes, and the m/z range 350-513 was used for PLS2. Accuracy was tested by recovery experiments and by inductively coupled plasma (ICP)-MS analysis. RESULTS: When compared with direct analyte signal measurements, application of IS yielded enhanced analytical performance using either UC or PLS2; the method quantification limits were: 11.1 µg L-1 , 23.4 µg L-1 for Cu and 89.8 µg L-1 , 97.1 µg L-1 for Pb, respectively. In tequila, MALDI-TOFMS and ICP-MS provided consistent results for Cu (165-2599 µg L-1 ); Pb was not detected in any sample by MALDI-TOFMS, yet recoveries obtained after standard addition were indicative of acceptable accuracy (400 µg L-1 Pb added; recoveries: 91.2-108% for UC and 98.8-120% for PLS2). CONCLUSIONS: New experimental evidence has been provided supporting the inclusion of trace metals quantification within a range of MALDI-TOFMS applications. Slightly better results were obtained for UC as compared with PLS2 yet both methods can be recommended for testing the compliance of Cu and Pb levels with Official Mexican Norm. Of note, while using PLS2, there is no need for signal integration nor for IS normalization.

New seven membered palladacycles: C-Br bond activation of 2-bromo-pyridine derivative by Pd(II).

C-Br bond activation followed by a C-C coupling reaction of the 2-bromo-pyridyl unit of [1-phenyl-2-(6-bromopyridin-2-yl)-benzoimidazole] was performed by Pd(CH(2)CMe(2)-o-C(6)H(4))(η(4)-COD). Two new seven membered palladacycles were obtained. A combined experimental and theoretical DFT study elucidates the mechanism for this reaction.

Iridium(III)-induced isomerization of 2-substituted pyridines to N-heterocyclic carbenes.

Steric strains (F-strain or front-strain) in the acid-base interaction between the Lewis acid [TpMe2Ir(C6H5)2] and 2-substituted pyridines Lewis bases, are responsible for the stabilization of the C-adducts (2) of the respective pyridine carbene tautomers over the expected N-adducts.

Unusual fragmentation of CH2Cl2 by an Ir(III) centre bonded to a doubly metalated Tp(Ms) Ligand (Tp(Ms) = hydrotris(3-mesitylpyrazol-1-yl)borate).

The Ir(III) compound Tp(Ms'')Ir(N2), that contains a pentadentate, doubly metalated 3-mesityl substituted tris(pyrazolyl)borate ligand, induces the cleavage of C-H and C-Cl bonds of CH2Cl2 to yield a highly electrophilic chlorocarbene Ir=C(H)Cl complex.