Deboronation-Induced Ratiometric Emission Variations of Terphenyl-Based Closo-o-Carboranyl Compounds: Applications to Fluoride-Sensing.

Closo-o-carboranyl compounds bearing the ortho-type perfectly distorted or planar terphenyl rings (closo-DT and closo-PT, respectively) and their nido-derivatives (nido-DT and nido-PT, respectively) were synthesized and fully characterized using multinuclear NMR spectroscopy and elemental analysis. Although the emission spectra of both closo-compounds exhibited intriguing emission patterns in solution at 298 and 77 K, in the film state, closo-DT mainly exhibited a π-π* local excitation (LE)-based emission in the high-energy region, whereas closo-PT produced an intense emission in the low-energy region corresponding to an intramolecular charge transfer (ICT) transition. In particular, the positive solvatochromic effect of closo-PT and theoretical calculation results at the first excited (S1) optimized structure of both closo-compounds strongly suggest that these dual-emissive bands at the high- and low-energy can be assigned to each π-π* LE and ICT transition. Interestingly, both the nido-compounds, nido-DT and nido-PT, exhibited the only LE-based emission in solution at 298 K due to the anionic character of the nido-o-carborane cages, which cannot cause the ICT transitions. The specific emissive features of nido-compounds indicate that the emissive color of closo-PT in solution at 298 K is completely different from that of nido-PT. As a result, the deboronation of closo-PT upon exposure to increasing concentrations of fluoride anion exhibits a dramatic ratiometric color change from orange to deep blue via turn-off of the ICT-based emission. Consequently, the color change response of the luminescence by the alternation of the intrinsic electronic transitions via deboronation as well as the structural feature of terphenyl rings indicates the potential of the developed closo-o-carboranyl compounds that exhibit the intense ICT-based emission, as naked-eye-detectable chemodosimeters for fluoride ion sensing.

Selective separation of fluorinated compounds from complex organic mixtures by pyrolysis-comprehensive two-dimensional gas chromatography coupled to high-resolution time-of-flight mass spectrometry.

The usefulness of comprehensive two-dimensional gas chromatography (GC×GC) was demonstrated for the selective separation of fluorinated compounds from organic mixtures, such as kerosene/perfluorokerosene mixtures, pyrolysis products derived from polyethylene/ethylene-tetrafluoroethylene alternating copolymer mixture and poly[2-(perfluorohexyl)ethyl acrylate]. Perfluorocarbons were completely separated from hydrocarbons in the two-dimensional chromatogram. Fluorohydrocarbons in the pyrolysis products of polyethylene/ethylene-tetrafluoroethylene alternating copolymer mixture were selectively isolated from their hydrocarbon counterparts and regularly arranged according to their chain length and fluorine content in the two-dimensional chromatogram. A reliable structural analysis of the fluorohydrocarbons was achieved by combining effective GC×GC positional information with accurate mass spectral data obtained by high-resolution time-of-flight mass spectrometry (HRTOF-MS). 2-(Perfluorohexyl)ethyl acrylate monomer, dimer, and trimer as well as 2-(perfluorohexyl)ethyl alcohol in poly[2-(perfluorohexyl)ethyl acrylate] pyrolysis products were detected in the bottommost part of the two-dimensional chromatogram with separation from hydrocarbons possessing terminal structure information about the polymer, such as α-methylstyrene. Pyrolysis-GC×GC/HRTOF-MS appeared particularly suitable for the characterization of fluorinated polymer microstructures, such as monomer sequences and terminal groups.

[Exploration of demonstration and promotion experiment of fluorine fixation technology during coal burning].

OBJECTIVE: To demonstrate and promote the fluorine-fixing technology of the coal burning on a calcium-based compound as the additive for briquettes made in the coal-burning fluorosis area, in order to evaluate the effects of fluorine-fixing and indoor air pollutants condition. METHODS: The briquettes added calcium-based fluorine sorbent were used for heating and cooking. In the meantime, the figures on various components in briquettes and fluorine content in coal slag as well as concentrations of indoor air fluorides, sulfur dioxide and PM10 were calculated. RESULTS: On the basis of the coal burning fluorine-fixing pilot experiment, 100 households in Longli County, Guizhou Province were selected as the experimental group for coal burning fluorine-fixing demonstration and promotion. When the burning calcium-based fluorine-fixing bitumites were made into coalballs, the average fluorine-fixing ratios in demonstration and promotion were 77.26%. The average reduction ratios of indoor air pollutants, fluorides were 53.3% -73.8%, sulfur dioxide were 62.8% -91.1% and PM10 were 9.5% -41.4%. There were 10% increases in the cost of briquettes due to the addition of calcium-based fluorine sorbent in demonstration and promotion. CONCLUSION: The preparation process of calcium-based fluorine-fixing briquettes was simple and highly flammable and it was applicable to regions abundant in bitumite.

Separation of complex mixtures of fluorobenzoic acids by capillary electrophoresis.

Fluorobenzoic acids are important intermediates in the synthesis of antibacterial drugs. Conditions for the separation of mixtures of twenty-five acids by CE have been optimized. A set of conditions with phosphate buffer (pH 3.1), successive multiple ionic-polymer layer (SMIL) coating capillary, and negative separation voltage provided a short time separation based on the difference in the acidic dissociation constant (pK(a)) of the sample acids. Addition of ACN to the separation solution improved the selectivity resulting in a broader distribution of migration times of the samples. The addition of tetradecyltrimethylammonium chloride below the CMC was also effective in changing the migration pattern of fluorobenzoic acids. Furthermore, practical utility was demonstrated through quantitative studies on the optimized condition including the durability of the SMIL coating.

Reverse fluorous solid-phase extraction: a new technique for rapid separation of fluorous compounds.

Fluorous-tagged compounds can rapidly be separated from organic (non-tagged) compounds by the new separation technique of reverse fluorous solid-phase extraction (r-fspe). In a reversal of the roles of solid and liquid phases in standard fluorous spe, a mixture is charged to a polar solid phase (standard silica gel) and then eluted with a fluorous solvent or solvent mixture. The organic components of the mixture are retained, while the fluorous components pass. [structure: see text]