Synthesis and properties of polymers containing sprio(indoline-isoxazoline)

Polymers containing spiro(indoline-isoxazoline) nuclei were prepared by 1,3-dipolar cycloaddition reactions of N,N′-alkylene-bis-3,3-dimethyl-2-methyleneindolines with bis-hydroxamic chlorides. Irradiation of the polymers with UV in solution resulted in novel skeletal rearrangements and resulted in polymers containing benzo-1,5-diazocine-2-one nuclei. Photoconductivities of the polymers were also studied.     

PHOTOVOLTAIC PROPERTIES OF MESO-TETRAARYLPORPHYRINS

Abstract— The photovoltaic properties of meso -tetraphenylporphyrin and its derivatives with various para -substituents, meso-tetrakis(2,4-dimethoxyphenyl)porphyrin and meso -tetrakis (2-fluorenyl)porphyrin have been investigated. The forward dark current-voltage characteristics of Al/porphyrin/Ag cells are attributed to the MIS Schottky barriers consisting of Al/Al₂O₃/porphyrin. The barrier parameters such as the apparent diffusion potential V ₀ the barrier width w₀ and the density of ionized impurity N are estimated by using the capacitor discharge method. The action spectra of photocurrents closely follow the optical absorption spectra of the porphyrin films. The photocurrents vary as i _pα I ^γ, where I is the incident light intensity, and the Sight exponents y range between 0.83 and 1.0. The sublinear difference from unity could be related to the exponential distribution of hole traps in films of the porphyrins. No obvious correlation between the photocurrent and the fluorescence quantum yields of the sublimed porphyrin films is found. The electron donating substituents such as OCH₃ and CH₃ strikingly increase the photocurrents. The photocurrent quantum yields correlate exponentially with the first ring oxidation potentials of the porphyrins and also with the substituent constants for the Hammett linear free-energy relationship. The current quantum yields estimated for the porphyrins studied, range in the order of 10^-4–10^-2 with power conversion efficiencies 10^-7–10^-3.     

Sesquiterpenoids and Lactone Derivatives from Ligularia dentata

Seven new compounds were isolated from the roots of Ligularia dentata, including five bisabolane‐type sesquiterpenoids (bisabolane=1‐(1,5‐dimethylhexyl)‐4‐methylcyclohexane), namely (8β,10α)‐8‐(angeloyloxy)‐5,10‐epoxybisabola‐1,3,5,7(14)‐tetraene‐2,4,11‐triol ( 1 ), (8β,10α)‐8‐(angeloyloxy)‐5,10‐epoxythiazolo[5,4‐a]bisabola‐1,3,5,7(14)‐tetraene‐4,11‐diol ( 2 ), (1α,2α,3β,5α,6β)‐1,5,8‐tris(angeloyloxy)‐10,11‐epoxy‐2,3‐dihydroxybisabol‐7(14)‐en‐4‐one ( 3 ), (1α,2α,3β,5α,6β)‐2,5,8‐tris(angeloyloxy)‐10,11‐epoxy‐1,3‐dihydroxybisabol‐7(14)‐en‐4‐one ( 4 ), and (1α,2β,3β,5α,6β)‐1,8‐bis(angeloyloxy)‐2,3‐epoxy‐5,10‐dihydroxy‐11‐methoxybisabol‐7(14)‐en‐4‐one ( 5 ) (angeloyloxy=[(2Z)‐2‐methyl‐1‐oxobut‐2‐enyl]oxy), and two lactone derivatives, (2α,3β,5α)‐2‐(acetyloxy)‐9‐methoxy‐5‐(methoxycarbonyl)‐2,3‐dimethylheptano‐5‐lactone ( 6 ), and (2β,4β)‐2‐ethyl‐5‐hydroxy‐5‐(methoxycarbonyl)‐4,5‐dimethylpentano‐4‐lactone ( 7 ) (α/β denote relative configurations), together with (2E,4R,5S)‐2‐ethylidene‐5‐(methoxycarbonyl)‐4‐methylhexano‐5‐lactone ( 8 ), a known synthetic compound. Compound 2 is the first sesquiterpenoid derivative containing the uncommon benzothiazole moiety. The structures of 1 – 8 were established by spectroscopic methods, especially 2D‐NMR and MS analyses.     

Tuning of spin crossover equilibrium in catecholatoiron(III) complexes by supporting ligands

Introduction of electron-withdrawing groups on co-ligands effectively raises the spin crossover temperature of catecholatoiron(III) complexes and induces a significant amount of the low spin species in solution even at around room temperature.     

Daily variation in cellular content of UV-absorbing compounds mycosporine-like amino acids in the marine dinoflagellate Scrippsiella sweeneyae

Sudden exposure experiments to high PAR (photosynthetically available radiation) or high PAR+UVR (ultraviolet radiation) were conducted for the marine dinoflagellate Scrippsiella sweeneyae acclimated to either low PAR or high PAR to determine the induction of cellular mycosporine-like amino acid (MAA) in relation to photosynthesis status. When the exposure to high PAR (30.8 Wm(-2)) was provided at different time in the light period for S. sweeneyae acclimated to low PAR (7.7 Wm(-2)) which suppressed photosynthesis, S. sweeneyae could enhance the induction of MAA but it only occurred in the first half of the light period. When UVR exposure was provided for the culture acclimated to high PAR which enhanced photosynthesis, cellular MAA content did not increase during the entire light period, but displayed daily variation similar to the control for two and half days. Daily variation of cellular MAA content did not synchronized with that of cell volume and cellular chlorophyll a content. The individual MAAs also revealed similar daily variations with different phase, which increased for a few hours in the beginning of the light period, except for cellular palythine content. Thus the total cellular MAA content revealed daily variation with changing the relative composition within a few hours. As one of the biological protective strategies against harmful UVR in sunlight, the daily vertical migration in the bloom forming dinoflagellates might be accompanied by the daily variation of cellular MAA content for a photosynthesis at daytime.     

The newborn surface of dull metals in organic synthesis. Bismuth-mediated solvent-free one-step conversion of nitroarenes to azoxy- and azoarenes

When milled together with bismuth shots, nitroarenes are readily converted to azoxy- and/or azoarenes depending on substrates and conditions employed. Simple extraction with organic solvent followed by evaporation of the resulting dark pasty solid gave the product in good yield.     

Oxygenative cleavage of catechols including protocatechuic acid with molecular oxygen in water catalysed by water-soluble non-heme iron(III) complexes in relevance to catechol dioxygenases

Catechol dioxygenase model oxygenations have been performed for the first time in water by using water-soluble nonheme iron(III) complexes, enabling the oxygenation of protocatechuic acid and other catechols.