Synthesis and optical properties of fluorene‐based polymers incorporating organosilicon unit

The synthesis and optical properties of polymers bearing the repeating unit of terfluorene and various organosilicon groups were investigated. Polymers with high molecular weight and good solubility could be obtained by Suzuki coupling polymerization from silylene‐containing fluorene‐based dibromo monomers and 9,9‐dihexylfluorene‐2,7‐bis(trimethyleneborate). From UV spectra of polymers bearing acyclic silylene bridge, the organosilicon units not only interrupted a π‐conjugation but also contributed to an electronic communication between connected fluorenes. The emission maximum wavelengths (ca. 400 nm) blue‐shifted when compared with that of polyfluorene (418 nm) and the fluorescence quantum yields were considerably high (>0.82) in the CHCl₃ solution. On the other hand, rather broad emission was observed at 480 nm and the fluorescence quantum yield was quite low (0.004) in the solution‐state PL spectrum of tetraphenylsilole‐containing polymer. The polymer emitted visible green light in the spin‐coated film. The fluorescence peak intensity at 486 nm gradually decreased when the film was illuminated with the UV light of 359 nm in air. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4786–4794, 2007     

Chromogenic crown ether reagents for spectrophotometric determinations of sodium and potassium

Crown ethers carrying a phenolic group, 2-hydroxyphenoxymethyl-15-crown-5 and -18-crown-6, were synthesized. Introduction of nitro groups in the 3- and 5-positions of the aromatic nucleus or introduction of a 4-nitrophenylazo group in the 5-position gives a series of chromogenic reagents suitable for the extraction spectrophotometry of sodium and potassium. Sodium in human blood serum was successfully determined by using the (2-hydroxy-3,5-dinitrophenyl)oxymethyl-15-crown-5 reagent. The molar absorptivity of the sodium complex is 14 000 l mol^-1 cm^-1 at 423 nm.     

Hydrolysis of 4-cyano-1-ethoxypyrimido[1,6-a]benzimidazole: Formation of a ynaminonitrile and benzimidazolidines

The title compound 4 was hydrolyzed to a new type of ynaminonitrile 5 and benzimidazolidines 7 and 9 under acidic or basic conditions. Reaction mechanisms were proposed.     

Characterization of Pyrene Photoproducts in Chloroform by Gas-Chromatography and Gas-Chromatography Mass-Spectrometry

Photoproducts resulting from illumination of a pyrene-chloroform solution using several light sources (sunlight, lamp, a pulsed laser) were analyzed by using gas chromatography (GC) and GC-mass spectrometry. The main photoproducts in chloroform were chloropyrene and pyrenecarboxaldehydes, and their relative yields depended on differences in illumination conditions. Chloropyrene was formed under all types of light illumination, while ultraviolet lights was required for the formation of pyrenecarboxaldehydes. Several reaction mechanisms are proposed to account for the formation of chloropyrene and pyrenecarboxaldehydes.     

Photooxygenation of pyrazin-2(1h)-ones

1-Alkyl-5,6-diphenylpyra2in-2(1H)-ones (1a-b) reacted with singlet oxygen in dichloromethane to afford the stable endoperoxide (1a-b), while in methanol to afford the 1:1-adduct (3a-b) of the endoperoxide (2a-b) and methanol.     

Synthesis of Δ1[9]- and/or Δ8[9]-dehydroindolizidines and related compounds

A facile synthesis of Δ^1[9]- and/or Δ^8[9]-dehydroindolizidine and related compounds, consisting of dry distillation of γ-(N-2-piperidinonyl)butyric acid over soda-lime, is described. Reductions of these dehydroindolizidines and stereochemistry of 1-methylindolizidine are also described.