Cyclodextrin-enclosed substances of Brazilian propolis

By using beta-cyclodextrin-inclusion as a unique technique, an efficient separation of pharmacologically active phenolic compounds from Brazilian propolis was achieved to provide one new compound, 3-(3-hydroxy-3-methyl-butyl)-5-prenyl-4-hydroxycinnamic acid, together with two common cinnamic acid derivatives, artepillin C and capillartemisin A, and two known flavanols, aromadendrin and 3,5,7-trihydroxy-4'-methoxyflavanol.     

PHOTOCHEMICAL cis/trans ISOMERIZATION OF AN AMPHIPHILIC MEROCYANINE DYE IN HOMOGENEOUS SOLUTION AND REVERSED MICELLES

Abstract— In the present study, the photochemical cis⇌trans isomerization of the amphiphilic merocy-anine dye (4-hydroxy-l-cetyl stilbazolium betaine C₁₆M) is reported. The structure of each isomer is established from high resolution FT ¹H-NMR analysis. The photochemical quantum yields φ_t→c, and φ_c→t are determined in methanol and in reversed micelles of the system (CDBA, benzene, water). The quantum yield φ_c→t increases in reversed micelles compared to that in methanol. The reverse results are obtained for φ_t→c. The micellar effect on the photochemical trans→cis isomerization will be discussed.     

Chemical Factors That Influence the Production of Conductive and/or Reflective Silver-Doped Polyimide Films

ABSTRACT

Doping a poly(amide acid) resin with a silver containing additive (1,5-cyclooctadiene-hexafluoroacetylacetonato)-silver(I) [Ag(COD) (HFA)] resulted, after thermal cure, in either a highly reflective or highly eléctrically conductive polyimide film. The combination of monomers, which render films with low T_g (~210°C), and contained sulfur, produced films with surface resistance in the range 10^1–10³ ohms. On the other hand, films with specular reflectivity (relative to a silver mirror) in the range of 65–48% were obtained using both high T_g polyimides and polyimides void of sulfur in the polyimide backbone with low T_g. Our understanding regarding the structure-property relationship on these polyimide films and also the characterization of the doped-films are discussed.     

Photophysical properties and semiempirical calculations of perylene-3,4,9,10-tetracarboxylic tetramethylester (PTME)

The spectral behavior and fluorescence quantum yield of perylene-3,4,9,10-tetracarboxylic tetramethylester (PTME) have been measured in different solvents. Both electronic absorption and fluorescence spectra are not sensitive to medium polarity. The dye exhibits high fluorescence quantum yield and high photostable. Crystalline solid of PTME gives excimer-like emission at 530 nm. The laser activity of PTME has been investigated. The dye solution in N,N-dimethylformamide (DMF) gives laser emission around 480 nm upon excitation by 337.1 nm nitrogen laser pulse. The excitation energy transfer from 7-dimethylamino-4-methylcoumarine (DMC) to PTME has also has been studied and the value of energy transfer rate constant, k(ET), and critical transfer distance, R(0) indicate a F?rster-type mechanism. The photodecomposition of PTME in chloromethane solvents has been also studied. We applied semiempirical MO calculations using (PM3 and ZINDO-CI) calculations to explain the geometric and electronic behaviors of the PTME molecule in both ground and excited states and make a correlation with the experimental observations.     

Synthesis and properties of stereoregular fluoro-polymers via ring-opening metathesis polymerization of fluorinated norbornenes and norbornadienes. An overview and progress report

Since the first report of the ring-opening metathesis polymerization of fluorinated monomers in 1979 considerable advances in precision and control of such syntheses have been achieved through the introduction of well defined initiators. It is now possible to carry out well controlled living and stereoregular polymerizations. The products of such syntheses can display unusually high relaxed dielectric constants, an observation which is crucial to the assignment of their tacticities and probably significant with regard to possible applications of this type of material.