First Time. (first + time)

Distribution by Scientific Domains


Selected Abstracts


Ultrafast Vibronic Processes in a Ru,Porphyrin Complex

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 31 2008
Izumi Iwakura
Abstract The excited-state dynamics of RuII(TPP)(CO)(acetone) (TPP = tetraphenylporphyrin) was investigated by using a sub-5-fs pulse. In previous studies, the fluorescence lifetime of RuII(TPP)(CO) could not be resolved and was reported to be <1 ps. Analysis of the six-coordinate complexes of RuII(TPP)(CO)(acetone) showed that 1Qx(,,,*) had a lifetime of 140,±,20 fs and the lifetime of 3(d,,*) was 560,±,150 fs. Stimulated emission due to a spin-forbidden transition from 3(,,,*) to the ground state was observed for the first time.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]


The Use of a Bifunctional Copper Catalyst in the Cross-Coupling Reactions of Aryl and Heteroaryl Halides with Terminal Alkynes

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 23 2008
Minyan Wu
Abstract Copper-catalyzed cross-coupling reactions of aryl halides and heteroaryl halides with terminal alkynes were carried out in DMF at 110,130 °C to provide the corresponding coupling products in satisfactory-to-good yields by using inexpensive 8-hydoxyquinoline as the ligand. Noteworthy is that the bifunctional copper catalyst was successfully applied in this alkynylation reaction for the first time.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]


Kinetics and mechanism of the dehydration reaction of sarcosine to a bislactame through diacyclperoxide intermediate in strong acidic medium

INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 11 2009
Homayoon Bahrami
The influence of substitution on the amine functional group of glycine in the permanganic oxidation of such an ,-amino acid in moderately concentrated sulfuric acid medium has been investigated. Reaction products analysis has revealed that contrary to the usual ,-amino acid oxidation product, which is an aldehyde species, a valuable compound, namely 1,4-dimethylpiperazine-2,5-dione, has been obtained as the main product via a cheap, simple, efficient, and novel method. Sarcosine has been chosen as a substituted derivative of glycine, and the kinetics and mechanism of its permanganic oxidation have been investigated using a spectrophotometric technique. Conclusive evidence has proven delayed autocatalytic activity for Mn(II) in this reaction, analogous to some ,-amino acids. It has been revealed that such activity can show up when a certain concentration ratio of Mn(II) to sarcosine is built up in the medium, which we call the "critical ratio." The magnitude of the latter ratio depends on the sulfuric acid concentration. Considering the "delayed autocatalytic behavior" of Mn(II) ions, rate equations satisfying observations for both catalytic and noncatalytic routes have been presented. The reaction shows first-order dependence on permanganate ions and sarcosine concentrations in both catalytic and noncatalytic pathways, and apparent first-order dependence on Mn2+ ions in catalytic pathways. The correspondence of pseudo-order rate constants of the catalytic and noncatalytic pathways to Arrhenius and Eyring laws has verified "critical ratio" as well as "delayed autocatalytic behavior" concepts. The activation parameters associated with both pathways have been computed and discussed. Mechanisms for both catalytic and noncatalytic routes involving radical intermediates as well as a product having a diketopiperazine skeleton have been reported for the first time. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 689,703, 2009 [source]


Production of gliotoxin on natural substrates by Trichoderma virens

JOURNAL OF BASIC MICROBIOLOGY, Issue 1 2005
R. Anitha Dr.
Gliotoxin, an epithiodiketopiperazine toxin produced by the ,Q' strain of Trichoderma virens is essential for curtailing growth and multiplication of phytopathogens (Howellet al. 1993, Fravel 1988). Three isolates (Gv, Gv-A and Gv-V) of Trichoderma virens were grown on natural substrates such as bengal gram hull, gingelly cake, green gram hull, rice bran, soya meal, sugarcane bagasse, soyameal + tapioca, tapioca powder, tapioca peel and wheat bran). It was evident from this study that maximum gliotoxin (64 mg/l) was produced on tapioca powder by the alien isolate Gv. However sugarcane bagasse significantly enhanced gliotoxin production (36 mg/l) in the native isolate Gv-A, when compared to other substrates like greengram hull and rice bran. So far, studies on production of gliotoxin on synthetic media has been reported. We report the production of gliotoxin by T. virens on natural substrates "in vitro" for the first time. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


resonance enhancement of photoluminescence from silicon nanocrystallites

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 2 2009
L. V. Belyakov
Abstract An interaction of molecular oxygen and p-Si nanocrystallites in HF,ethanolic solution with simultaneous illumination has been investigated. It is shown that after such treatment with white-light exposure the photoluminescence from nanocrystallites enhances substantially caused by photogenerated singlet forms of molecular oxygen. In the case of monochromatic illumination with photon energy in the range 2.5,0.95 eV dependence of photoluminescence intensity after the treatment on photon energy used shows resonant peaks corresponding to the absorbance peaks of excited molecular oxygen. To our knowledge such photoluminescence peaks in porous silicon spectroscopy have been observed for the first time. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Phase transition and elasticity of CdO under pressure

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 1 2009
Feng Peng
Abstract First-principles calculations of the crystal structures, and phase transition, and elastic properties of cadmium oxide (CdO) have been carried out with the plane-wave pseudopotential within the generalized gradient approximation in the frame of density functional theory method. The calculated values (for crystal structures) are in good agreement with experimental data as well as with some of the existing model calculations. For CsCl-type CdO, the dependence of the elastic constants cij, the aggregate elastic modulus (B, G, E), and the elastic anisotropy on the pressure have been investigated. Moreover, the pressure dependences of the Poisson ratio, Debye temperature, and the compressional and shear elastic wave velocities have been investigated for the first time. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]