Enhanced emission and its switching in fluorescent organic nanoparticles

A new class of organic nanoparticles (CN-MBE nanoparticles) with a mean diameter of ca. 30-40 nm, which exhibit a strongly enhanced fluorescence emission, were prepared by a simple reprecipitation method. CN-MBE (1-cyano-trans-1,2-bis-(4'-methylbiphenyl)ethylene) is very weakly fluorescent in solution, but the intensity is increased by almost 700 times in the nanoparticles. Enhanced emission in CN-MBE nanoparticles is attributed to the synergetic effect of intramolecular planarization and J-type aggregate formation (restricted excimer formation) in nanopaticles. On/off fluorescence switching for organic vapor was demonstrated with CN-MBE nanoparticles.     

Syntheses of polyurethanes derived from oximes and their photodegradation

Polyoxime-urethanes have been synthesized from dioximes and diisocyanates, and their structures have been ascertained by elemental analysis and infrared spectroscopy. They can be represented by the general formula: These polymer films were photolyzed by using a high-pressure 100-W mercury lamp, and the rate of decomposition of the N? O bond was determined by use of ultraviolet and infrared spectra, or comparing the photochemical behavior with that of corresponding model compounds. Upon irradiating these polymers in the presence or absence of sensitizers or a hydrogen donor, there were obtained photolyzed polymers of low molecular weight, of which the molecular weights were estimated by observing the viscosity changes. To deduce the mechanism of photodegradation of polyoxime-urethane, photolysis of benzophenone oxime-phenyl urethane was investigated as a model compound.     

Biomimetic alcohol oxidations by an iron(III) porphyrin complex: relevance to cytochrome P-450 catalytic oxidation and involvement of the two-state radical rebound mechanism

The systematic oxidation reactions of a wide range of alcohols have been carried out by using an iron porphyrin complex in order to understand their relation to cytochrome P-450 enzymes and to have a practical application to organic synthesis. The iron porphyrin complex catalyzed efficiently alcohol oxidation to the respective carbonyl compound via a high-valent iron-oxo porphyrin intermediate ((Porp)Fe=O+). Several mechanistic studies such as isotope 18O labeling, deuterium isotope effect, linear free energy relationship, and ring-opening of radical clock substrate, have suggested that the alcohol is oxidized by a sequence of reactions involving an alpha-hydroxyalkyl radical intermediate and oxygen rebound to form the gem-diol, dehydration of which yields the carbonyl compounds. Moreover, it has been proposed that a two-state reactivity mechanism can also be adopted for alcohol oxidation reactions in iron porphyrin model systems as exhibited by P-450 enzymes.     

Redetermination of (6R,7S,9S,11S)‐(–)‐sparteinium monoperchlorate

The structure of the title compound, C₁₅H₂₇N₂⁺·ClO₄^?, consists of a monoprotonated sparteinium cation and a perchlorate anion. The two tertiary N atoms of the cation, one perchlorate O atom and a H atom form a bifurcated hydrogen bond, the four hydrogen‐bonding atoms being nearly in the same plane.     

Syntheses and reactivity of the diselenido molybdenum-manganese complex CpMoMn(CO)5(mu-Se2)

Reaction of CpMoMn(CO)(8) with elemental selenium and Me(3)NO in the absence of light yielded the diselenido complex CpMoMn(CO)(5)(mu-Se(2)), 2. Compound 2 contains a bridging diselenido ligand lying perpendicular to the Mo-Mn bond, Mo-Mn = 2.8421(10) A. In the presence of room light, the reaction yielded the tetranuclear metal complex Cp(2)Mo(2)Mn(2)(CO)(7)(mu(3)-Se)(4), 3 (36% yield), and 2 (7% yield). Compound 2 reacted with ethylene to yield the ethanediselenato complex CpMoMn(CO)(5)(mu-SeCH(2)CH(2)Se), 4, by insertion of ethylene into the Se-Se bond. Compound 2 also reacted with (PPh(3))(2)Pt(PhC(2)Ph) and CpCo(CO)(2) to yield the complexes CpMoMnPt(PPh(3))(2)(CO)(5)(mu(3)-Se)(2), 5, and Cp(2)CoMoMn(CO)(5)(mu(3)-Se)(2), 6, respectively, by insertion of the metal groupings CpCo and Pt(PPh(3))(2) into the Se-Se bond of 2. The oxo compound Cp(2)CoMo(O)Mn(CO)(5)(mu(3)-Se)(2), 7, was obtained from 6 by decarbonylation at molybdenum by using Me(3)NO. The molecular structures of the complexes 2-7 were established by single-crystal X-ray diffraction analyses.     

Study of hydantoin. III . Mass spectrometric behaviour in the electron impact of 2-imino-4-thiazolidinone derivatives

The mass spectral decomposition modes of a series of 2-imino-4-thiazolidinone derivatives are reported and discussed. The fragmentation patterns and mechanisms postulated have been confirmed by the analysis of the MIKE spectra and using DADI technique and the effects of heteroatoms and substituents on the MIKE spectrum of these compounds are compared with that of 3-substituted hydantoins.     

Briarane diterpenoids from the formosan gorgonian Coral Junceella fragilis

A new trihydroxy briarane-related diterpenoid, junceellolide I (1), along with a known metabolite, (1R,2R,5Z,7R,8S,9R,10R,12R,14R,17S)-2,14-diacetoxy-8,17-epoxy-9,12-dihydroxybriara-5,11(20)-dien-19-one (2), have been isolated from the gorgonian coral Junceella fragilis, collected off the southern Taiwan coast. The structure, including the relative configuration of the new compound 1, was elucidated by the combination of spectral data, particularly in high-resolution 1H- and 13C-NMR spectroscopy utilizing COSY, HMBC, HMQC, and NOESY experiments.     

Modelling the electric double layer at electrode/electrolyte interfaces

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