ABSTRACT
Three series of linear extended benzofuran derivatives associating cyanovinyl unit and electron withdrawing systems such as paracyanophenyl (series 1) and pentafluorophenyl (series 2) units or the electron donor 3,4-dimethoxyphenyl (series 3) moiety have been prepared. The donor character of the benzofuran part is adjusted either without modifying the conjugation by adding electron-donating methoxy groups to positions 5 and 6 of the benzofuran (compounds BF2 and BF3) or by increasing the extension of the conjugation with the naphthofuran unit (BF4), and by the insertion of a furan ring between the benzofuran and the cyanovinylene bond (BF5). While most of the compounds show very low emission in solution, microcrystalline powders of almost all compounds show middle at strong emissions under excitation at 350-400â nm with emission colors ranging from blue - green to red. It is shown that this variation of the emission colors is essentially due to the type of stacking of the molecules in the solids for series 1 and 2. For series 3, it is above all the extension of the conjugation of the compounds which leads to the red shift.
ABSTRACT
In this study, the performances of silver-impregnated adsorbents prepared from different host supports (SBA-15, alumina, ceria, and faujasite Y zeolite) and calcined or not at 500 °C (1 h) were compared for the capture of I2 and CH3I. By keeping the silver content rather similar (about 15-17 wt %) among the sorbents, it was possible to assess the effect of silver dispersion and speciation on the adsorption capacities measured for both adsorbates. In a first part, several characterization techniques (XRD, DRS-UV-Vis, TEM, etc.) were used to probe the state of silver in the calcined and non-calcined materials. It was found that the characteristics of silver species are strongly influenced by the thermal treatment, the presence or absence of exchange sites, and the stability of the supports. Silver agglomeration was enhanced after calcination at 500 °C especially for supports bearing no exchange sites (SBA-15) or no ordered pores (alumina and ceria). Then, the adsorption performances of the studied silver sorbents were discussed in relation with their physicochemical characteristics. After-test characterizations were useful to assess the proportion of silver species that have reacted with CH3I and I2 to yield AgI precipitates. Depending on the adsorbate, different trends were obtained. I2 adsorption/reaction with silver sites was found to be quantitative (I/Ag ≈1), whatever the silver speciation and dispersion on the support. By contrast, a high proportion of cationic silver species was found essential to increase CH3I adsorption (I/Ag about 0.6-0.7 against 0.2-0.3 for Ag agglomerated species).
ABSTRACT
Two series of linear extended benzofuran derivatives associating cyanovinyl unit and phenyl or furan moieties obtained from benzaldehyde-lignocellulosic (Be series) or furaldehyde -saccharide (Fu series) platforms were prepared in order to investigate their emission and electrochemical properties. For the fluorescence in solution and solid states, contrasting results between the two series were demonstrated. For Be series a net aggregation induced emission effect was observed with high fluorescence quantum yield for the solid state. A [2+2] cycloaddition under irradiation at 350â nm was also revealed for one derivative of Be series. In contrast, for Fu series the fluorescence in solution is higher than in the solid state. The X-ray crystallography studies for the compounds reveal the formation of strong π-π stacking for the derivatives without emissive property in the solid state and the presence of essentially lateral contacts for emissive compounds. Taking advantage of the propensity to develop 2D π-stacking mode for the more extended derivative with a central furan cycle, organic field effect transistors presenting hole mobility have been made.
