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Coherent states via decoherence 总被引:1,自引:0,他引:1
17.
The molecular structure and properties of 7-azaindole in its first four singlet states were studied with a view to improving current understanding of the photophysical behavior of its C(2h) dimer. This dimer, which exhibits a double proton transfer via its two hydrogen bonds upon electronic excitation, has for 35 years been used as a model for the photophysical behavior of DNA base pairs. Electronic excitation of 7-azaindole simultaneously increases its acidity and basicity; these changes facilitate a concerted mechanism for the double proton transfer in the dimer. In this work, we found the acidity and basicity changes to occur only in its first pi,pi(*) excited singlet state. 相似文献
18.
Eulogio Jimenez Luis Romani Maria Inmaculada Paz Andrade Geneviève Roux-Desgranges Jean-Pierre E. Grolier 《Journal of solution chemistry》1986,15(11):879-890
Molar excess volumes V
E
at 25°C have been determined by vibrating-tube densimetry, as a function of mole fraction x for different series of an alkanoate (H
2m+1
C
m
COOC
n
H
2n+1
)+cyclohexane. Three types of alkanoates were investigated, i.e., methanoates (m=0, with n=3 and 4), ethanoates (m=1, with n=2, 3, and 4) and propanoates (m=2, with n=1, 2, and 3). In addition, a Picker flow calorimeter was used to obtain molar excess heat capacities C
p
E
at constant pressure at the same temperature. V
E
is positive for all systems and rather symmetric, with V
E
(x=0.5) amounting to almost identical values in a series of mixtures containing an alkanoate isomer of same formula (say C4H8O2, C5H10O2, or C6H12O2). The composition dependence of C
p
E
is rather unusual in that two more or less marked minima are observed for most of the mixtures, especially when the alkanoate is a methanoate or an ethanoate. These results are discussed in terms of possible changes in conformation of both the ester and cyclohexane. 相似文献
19.
A new steroidal saponin was isolated from the leaves of Agave attenuata. Its structure was established as (3beta,beta,25S)-spirostan-3-yl O-beta-D-glucopyranosyl-(1 --> 2)-beta-D-glucopyranosyl-(1 --> 2)-O-[beta-D-glucopyranosyl-(1 --> 3)]-beta-D-glucopyranosyl-(1 --> 4)-beta-D-galactopyranoside. The structural identification was performed using detailed analyses of 1H- and 13C-NMR spectra including 2D NMR spectroscopic techniques (COSY, HETCOR, and COLOC) and chemical conversions. The hemolytic activity of the steroidal saponin was evaluated using an in vitro assay. 相似文献
20.
Martin-Redondo MP Scoles L Sterenberg BT Udachin KA Carty AJ 《Journal of the American Chemical Society》2005,127(14):5038-5039
Reaction of [Pt(CH3)2(COD)] (COD = 1,5-cyclooctadiene) with Ph2PCCCCPPh2 led to a mixture of [{Pt(CH3)2}2(mu-Ph2PC4PPh2)2] (1) and [{Pt(CH3)2}3(mu-Ph2PC4PPh2)3] (2). Reaction of [PtCl2(COD)] with Ph2PCCCCPPh2 led to a mixture of the thermally unstable compounds [{PtCl2}2(mu-Ph2PC4PPh2)2] (3) and [{PtCl2}3(mu-Ph2PC4PPh2)3] (4) which transform into [{PtMe2}2{mu-C8(PPh2)4}] (5) and [{PtMe2}3{mu3-C12(PPh2)6}] (6) containing 8-membered diene-diyne and 12-membered triene-triyne rings, respectively. Compound 2 can be converted to [{PtMe2}3{C12(PPh2)6}] (7) by heating with CuCl at 80 degrees C, while 1 can be heated without significant cycloaddition. 相似文献