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991.
Peng X Komatsu N Kimura T Osuka A 《Journal of the American Chemical Society》2007,129(51):15947-15953
Chiral single-walled carbon nanotubes (SWNTs) have left- and right-handed helical structures (M and P, respectively, according to the IUPAC nomenclature). In this report, optically active SWNTs were obtained through preferential extraction of (M)- or (P)-SWNTs with 2,6-pyridylene-bridged chiral diporphyrins 1. In the circular dichroism (CD) spectra, the SWNTs extracted with 1 exhibit much larger intensity than those extracted with 1,3-phenylene-bridged chiral diporphyrins 2, indicating an improved chiral discrimination ability of 1. In particular, (6,5)-SWNTs display the most intensified CD signals among the SWNTs extracted with 1. In addition, the SWNT extraction ability of 1 has been shown to be considerably enhanced in comparison to 2. These improved discrimination and extraction abilities of 1 are attributed to the formation of its more stable SWNT complex. Computer-calculated energy minimized structures for 1:(6,5)-SWNT complexes show that (R)- and (S)-1 form complexes preferentially with (M)- and (P)-(6,5)-SWNTs, respectively. These calculations also predict that the 1:(6,5)-SWNT complex is approximately 1.6 kcal mol-1 more stable than the corresponding complex of 2, accounting for the improved abilities of 1 in the chiral discrimination and extraction. 相似文献
992.
Ono M Ishimatsu N Masuoka C Yoshimitsu H Tsuchihashi R Okawa M Kinjo J Ikeda T Nohara T 《Chemical & pharmaceutical bulletin》2007,55(4):632-634
Three new monoterpenoids, called genipacetal, genipamide, and genipaol, were isolated from the fruit of Genipa americana L. (Rubiaceae), along with the four known iridoids genipin, gardendiol, deacetyl asperulosidic acid methyl ester, and shanzhiside. Their chemical structures were determined on the basis of spectroscopic data. 相似文献
993.
Yang T Ju J Li G Yang S Sun J Liao F Lin J Sasaki J Toyota N 《Inorganic chemistry》2007,46(7):2342-2344
CoH2P2O7 and NiH2P2O7, which contain edge-sharing zigzag octahedral chains, were hydrothermally synthesized and structurally characterized. Both compounds exhibit field-induced metamagnetic behavior because of the strong intrachain ferromagnetic and relatively weak interchain antiferromagnetic interactions. 相似文献
994.
Hayashi N Kusano K Sekizawa S Shibata I Yasuda M Baba A 《Chemical communications (Cambridge, England)》2007,(46):4913-4915
Regio- and stereoselective hydrostannation of allenes by using di-n-butyliodotin hydride (Bu2SnIH) was accomplished to give alpha,beta-disubstituted vinyltins, which induced the synthesis of multi-substituted alkenes in a one-pot procedure. 相似文献
995.
Ju MJ Yang DH Takahara N Hayashi K Toko K Lee SW Kunitake T 《Chemical communications (Cambridge, England)》2007,(25):2630-2632
Highly sensitive and selective detection of 2,4-DNT, a representative explosive, was achieved by the synergic effect of molecular imprinting and host (cyclodextrin)-guest interaction in ultrathin layers of TiO(2) and SiO(2) gel; the detection limit using cSPI measurements reached nM concentration. 相似文献
996.
Benten H Guo J Ohkita H Ito S Yamamoto M Sakumoto N Hori K Tohda Y Tani K 《The journal of physical chemistry. B》2007,111(37):10905-10914
Intermoiety electronic interactions in the singlet and triplet excimer states of triply bridged [3.3.n](3,6,9)carbazolophanes ([3.3.n]Cz, n=3-6) were studied by emission and transient absorption measurements. In these [3.3.n]Cz molecules, the dihedral angle and the separation distance r between fully overlapped two carbazole rings change systematically from nearly parallel (n=3, r=3.35 A) to oblique (n=6, r=4.03 A). In rigid glass at 77 K, [3.3.n]Cz (n=3, 4) (r<4 A) exhibited red-shifted and structureless excimer fluorescence and phosphorescence while [3.3.n]Cz (n=5, 6) (r>4 A) exhibited monomer-like vibrational fluorescence and phosphorescence. In solution at 130 K, all [3.3.n]Cz molecules exhibited an excimeric fluorescence band while [3.3.5]Cz still exhibited monomer-like phosphorescence. Transient absorption spectra measured at 294 K exhibited local excitation and charge-transfer bands for all [3.3.n]Cz molecules in the excited singlet and triplet states, suggesting that not only singlet but also triplet excimers of carbazole are formed at room temperature. Furthermore, the singlet-triplet energy gap decreased with the decrease in n, suggesting that electrons are effectively delocalized over the two carbazole moieties. These findings showed that both singlet and triplet excimers of carbazole are formed with a separation distance shorter than about 4 A and are most stable in the parallel-sandwich structure and that the configurational mixing between exciton resonance and charge resonance states plays an essential role in the formation of singlet and triplet excimers of carbazole. 相似文献
997.
Nakamura K Hasegawa Y Kawai H Yasuda N Kanehisa N Kai Y Nagamura T Yanagida S Wada Y 《The journal of physical chemistry. A》2007,111(16):3029-3037
The luminescent and lasing properties of Eu(III) complexes were enhanced by using an dissymmetric Eu(III) complex. The photophysical properties (the emission spectral shapes, the emission lifetimes, the emission quantum yields, and the stimulated emission cross section (SEC)) were found to be dependent on the geometrical structures of Eu(III) complexes. The geometrical structures of Eu(III) complexes were determined by X-ray single crystal analyses. The symmetrical group of Eu(hfa)3(BIPHEPO) (tris(hexafluoroacetylacetonato)europium(III) 1,1'-biphenyl-2,2'-diylbis(diphenylphosphine oxide)) was found to be C1, which was more dissymmetric than Eu(hfa)3(TPPO)2 (tris(hexafluoroacetylacetonato)europium(III) 1,2-phenylenebis(diphenylphosphine oxide): C2 symmetry) and Eu(hfa)3(OPPO)2 (tris(hexafluoroacetylacetonato)europium(III) 1,2-phenylenebis(diphenylphosphine oxide): C2 symmetry). The analytical data were supported by Judd-Ofelt analysis. The most dissymmetrical Eu(III) complex, Eu(hfa)3(BIPHEPO), showed large electron transition probability and large SEC (4.64 x 10(-20) cm2). The SEC of Eu(hfa)3(BIPHEPO) was superior to even the values of Nd-glass laser for practical use (1.6-4.5 x 10(-20) cm2). The lasing properties of Eu(III) complexes in polymer thin film were measured by photopumping of a Nd:YAG laser (355 nm). The threshold energy of lasing oscillation was found to be 0.05 mJ. The increasing rate of the lasing intensity of Eu(hfa)3(BIPHEPO) as a function of the excitation energy was much larger than that of Eu(hfa)3(TPPO)2 and Eu(hfa)3(OPPO)2. The dissymmetrical structure of Eu(hfa)3(BIPHEPO) promoted the enhancement of the lasing property. 相似文献
998.
Effective rate constants for the surface reaction between solid methanol and deuterium atoms at 10 K
The surface reactions of CH3OH, CH2DOH, and CHD2OH with cold D atoms at 10 K were investigated using an atomic beam source and FTIR. Methyl-deuterated isotopologues CH2DOH, CHD2OH, and CD3OH were produced by exposure of amorphous solid CH3OH to D atoms at 10 K, and the pseudo-first-order rates for the reactions CH3OH + D --> CH2OH + HD, CH2DOH + D --> CHDOH + HD, and CHD2OH + D --> CD2OH + HD were estimated. The ratios of the reaction rates of the second and third reactions to the first reaction were 0.69 +/- 0.11 and 0.52 +/- 0.14, respectively. The difference in reaction rates is thought to be due to a secondary kinetic isotope effect on the H-abstraction reaction from the methyl side by D atoms. 相似文献
999.
1000.
Takaomi Suzuki Naoki Sugihara Eiichi Iguchi Katsuya Teshima Shuji Oishi Masayuki Kawasaki 《Crystal Research and Technology》2007,42(12):1217-1221
The specific surface free energy of ruby and quartz single crystal was experimentally obtained using contact angle of water and formamide droplets on the crystal surfaces, and compared with the morphology of each crystal. The ruby crystals satisfied Wulff's relationship even though their shape were not equilibrium form. The specific surface free energies of the growing faces of synthetic quartz crystal, ‐X, +X, Z, and S faces were obtained as 51.9, 55.6, 57.4, and 58.9 mN/m, respectively. The growth rates of these faces were 0.09, 0.23, 0.28, and 0.33 mm/day, respectively. The growth rate of each face of the quartz crystal can be regarded as a function of the experimentally obtained specific surface free energy. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献