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61.
Toru Egawa Yukari Kachi Tsuguhide Takeshima Hiroshi Takeuchi Shigehiro Konaka 《Journal of Molecular Structure》2003,658(3):241-251
The molecular structure and conformation of carvone, a compound with a minty odor, were investigated by means of gas electron diffraction supported by theoretical calculations. Electron diffraction patterns were recorded by heating the nozzle up to 128 °C to obtain enough scattering intensity. The infrared spectrum was also measured by using an absorption cell with a path length of 10 m. The obtained molecular scattering intensities were analyzed with the aid of theoretical calculations and infrared spectroscopy. It was revealed that the experimental data are well reproduced by assuming that carvone consists of a mixture of three conformers that have the isopropenyl group in the equatorial position and mutually differ in the torsional angle around the single bond connecting the ring and the isopropenyl group. It was also found that the puckering amplitude of the ring of carvone is close to those of menthol and isomenthol, a minty compound and its nonminty isomer. The determined structural parameters (rg and ∠α) of the most abundant conformer of carvone are as follows: 〈r(C-C)〉=1.520(3) Å; 〈r(CC)〉=1.360(5) Å; r(CO)=1.225(5) Å; 〈r(C-H)〉=1.104(4)Å; 〈∠CC-C〉=121.1(5)°; 〈∠C-C-C〉=110.4(5)°; ∠C-CO-C=117.1(14)°; 〈∠C-C-H〉=111.1(13)°. Angle brackets denote average values and parenthesized values are the estimated limits of error (3σ) referring to the last significant digit. 相似文献
62.
Enhancement of electronic excitation energy transfer in the colloidal crystals of colloidal silica suspensions doped with fluorescent dyes 总被引:1,自引:0,他引:1
Kiyoshi Shibata Hiroshi Kimura Akira Tsuchida Tsuneo Okubo 《Colloid and polymer science》2006,285(2):127-133
The efficiency of electronic excitation energy transfer from photo-excited rhodamine 110 (Rh110, energy donor) to rhodamine B (RhB, energy acceptor) in an exhaustively deionized colloidal silica suspension has been studied. This colloidal suspension shows Bragg reflection due to the formation of colloidal crystals and the Bragg-peak wavelength is controllable by the volume fraction of the silica spheres. When the Bragg-peak wavelength matches with the fluorescence band of Rh110, a depletion was observed in the Rh110 fluorescence spectrum. This means the fluorescence of Rh110 is partially trapped due to the Bragg reflection inside the crystal lattice. In the coexistence of RhB, the enhancement of RhB fluorescence intensity was observed. These facts clearly indicate the trapped photon energy of Rh110 is efficiently transferred to RhB within the colloidal crystals. The quantitative measurements showed that the enhancement of the transfer efficiency is 20% (or slightly more) in the present experimental conditions. 相似文献
63.
64.
Kinetics of chemiluminescence reactions of 2-methyl-6-phenylimidazo[1,2-a]pyrazin-3(7H)-one (1c, Cypridina luciferin analogue) and substituent effects of the 6-aryl group of derivatives 1 strongly suggest that the rate-determining step is a single electron transfer from an anion derived from 1 to a triplet molecular oxygen (O2) in the oxygenation process. 相似文献
65.
66.
The solubility of glycine,
-alanine,
-valine,
-leucine, and
-isoleucine in water was measured at 298.15 K and pressures up to 400 MPa. The standard deviation of the logarithm of the solubility is 0.001–0.003, equal to or better than the accuracy of atmospheric pressure measurement in the literature (0.001–0.05). A variety of solubility phenomena were observed. The solubility of glycine decreased with increasing pressure, whereas that of
-alanine increased. The
-valine and
-isoleucine have a solubility maximum at around 100 MPa, and
-leucine seems to exhibit a solid-phase phase transition at around 200 MPa. Pressure coefficient of the solubilities at 0.10 MPa is compared with that thermodynamically estimated in reference to aqueous density measurements of glycine and
-alanine at 298.15 K and 0.10 MPa, supporting a reliability of our high-pressure measurements. 相似文献
67.
68.
Yoshihiko Nishimori Katsuhiko Kanaizuka Dr. Masaki Murata Dr. Hiroshi Nishihara Prof. 《化学:亚洲杂志》2007,2(3):367-376
Films of linear and branched oligomer wires of Fe(tpy)2 (tpy=2,2′:6′,2′′‐terpyridine) were constructed on a gold‐electrode surface by the interfacial stepwise coordination method, in which a surface‐anchoring ligand, (tpy? C6H4N?NC6H4? S)2 ( 1 ), two bridging ligands, 1,4‐(tpy)2C6H4 ( 3 ) and 1,3,5‐(C?C? tpy)3C6H3 ( 4 ), and metal ions were used. The quantitative complexation of the ligands and FeII ions was monitored by electrochemical measurements in up to eight complexation cycles for linear oligomers of 3 and in up to four cycles for branched oligomers of 4 . STM observation of branched oligomers at low surface coverage showed an even distribution of nanodots of uniform size and shape, which suggests the quantitative formation of dendritic structures. The electron‐transport mechanism and kinetics for the redox reaction of the films of linear and branched oligomer wires were analyzed by potential‐step chronoamperometry (PSCA). The unique current‐versus‐time behavior observed under all conditions indicates that electron conduction occurs not by diffusional motion but by successive electron hopping between neighboring redox sites within a molecular wire. Redox conduction in a single molecular wire in a redox‐polymer film has not been reported previously. The analysis provided the rate constant for electron transfer between the electrode and the nearest redox‐complex moiety, k1 (s?1), as well as that for intrawire electron transfer between neighboring redox‐complex moieties, k2 (cm2 mol?1 s?1). The strong effect of the electrolyte concentration on both k1 and k2 indicates that the counterion motion limits the electron‐hopping rate at lower electrolyte concentrations. Analysis of the dependence of k1 and k2 on the potential gave intrinsic kinetic parameters without overpotential effects: k10=110 s?1, k20=2.6×1012 cm2 mol?1 s?1 for [n Fe 3 ], and k10=100 s?1, k20=4.1×1011 cm2 mol?1 s?1 for [n Fe 4 ] (n=number of complexation cycles). 相似文献
69.
Hiroshi Harada Kanichi Kamiya Hiroyuki Nasu Jun Matsuoka 《Journal of Sol-Gel Science and Technology》1997,10(3):291-300
The sodium dititanate, Na2O·2TiO2 glass was prepared by the sol-gel method. The structure of the glass, especially local environment of Ti4+ ions was examined using X-ray diffraction and X-ray absorption fine structure (XAFS) analyses, and was compared with that of the melt-derived glass with the same composition. It was found that Ti4+ ions are rather in five-fold coordination state, forming TiO5 pyramids with one doubly bonded Ti=O in the gel-glass, while they were in lower coordination state or four-fold coordination in the melt-derived glass. 相似文献
70.
Summary Pyridinium ylide complexes of methylcobaloxime were synthesized by the treatment of an ylide with Co(Hdmg)2 Me(SMe2). The crystal structure of one of the complexes, [Co(Hdmg)2Me C5H5NCHCOPh]C6H6 has been determined by x-ray diffraction techniques. The crystals are monoclinic, space group P21/c, witha = 10.456(5),b = 11.079(4),c = 24.58(1) Å, = 99.58(6), V = 2808 Å3, Z = 4. The Co-C (ylide) bond distance is 2.18 Å and Co-C(methyl) 2.04 Å. C(ylide)-Co-C(methyl) bond angle is 174.9°. The crystal, i.r. and1H n.m.r. data suggest that thetrans-influence of the ylide ligands is larger than that of py, Melm, OH2 or PPh3. 相似文献