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991.
1J(13C13C) has been determined in naturally abundant samples of η1,η2 -alkenyl-η5 -cyclopentadienylnickel complexes; for the coordinated double bonds 1J(CC) lies between the value for free ethylene and cyclopropane, and therefore gives direct insight into the relevant bonding situation. 相似文献
992.
Ewa Skrzypczak-Jankun Hanna Małuszyńska Anna Perkowska Zygmunt Kałuski 《Journal of chemical crystallography》1980,10(3-4):67-74
The formula of the title compound is C16H27ClN2O5,MW = 362.9 orthorhombic,P212121,a = 8.403(1),b= 13.133(1),c= 15.972(2) Å,Z = 4,D
x
= 1.37 g cm–3, (CuK) = 2.2 mm-1. The lupanine skeleton has atrans-trans configuration. The ringA has a half-chair conformation, theB andD rings adopt a chair form, and theC ring forms a boat. The lupanine cations are linked together by the intermolecular hydrogen bonds forming infinite chains alongb. The N(16) ... O(C2) distance is 2.763(7) Å. 相似文献
993.
Absorption and luminescence spectra, depopulation kinetics of the lowest excited singlet and triplet states and acid-base equilibria were investigated for neutral and protonated diazaphenanthrenes: 2,3-, 1,4- and 5,6-DAF. The spectroscopical results are correlated with CNDO/S calculations. Profound influence of topology upon photophysical and chemical (basicity) properties has been stated and discussed. 相似文献
994.
Marina Biagini Cingi Anna Maria Manotti Lanfredi Antonio Tiripicchio Marisa Tiripicchio Camellini 《Transition Metal Chemistry》1979,4(4):221-224
Summary The crystal structure of CuCl2(C7H8N4O2)(H2O)2 has been determined from diffractometer data by Patterson and Fourier methods and refined by full-matrix least-squares to R=0.067 for 2123 observed reflections. Unit cell constants are:a=9.930(8),b=9.987(8),c=7.483(6) Å,=123.2(1),=94.5(1),= 83.9(1)°. The space group is P¯1 withZ=2. The structure consists of diaquadichlorotheophyllinecopper(II) complexes linked by hydrogen bonds. The coordination polyhedron of copper is a square pyramid whose base, severely tetrahedrally distorted, is formed by a water molecule [Cu-Ow=2.025(7) Å], two chlorines [Cu-Cl=2.273(4), 2.296(4) Å] and an imidazole nitrogen [Cu-N=1.983(9) Å] from the theophylline ligand. A second water molecule is at the apex of the pyramid [Cu-Ow=2.292(7) Å]. Coordination is completed to a distorted octahedral one by a long Cu ... O=3.164(7) Å contact involving the exocyclic oxygen at C6 of the theophylline ligand. 相似文献
995.
Lidia Prajer-Janczewska Anna Postawka Krystyna Koćma Krystyna Rudolf 《Monatshefte für Chemie / Chemical Monthly》1968,99(3):1175-1176
Ohne ZusammenfassungMit 1 Abbildung 相似文献
996.
Alessandra Borrelli Marziano Marziani Anna Maria Rangoni 《Annali dell'Universita di Ferrara》1976,22(1):171-184
Riassunto Si studia l'influenza della polarizzazione delle radio-onde su alcuni fenomeni non lineari nella ionosfera tramite una nuova
e più completa relazione funzionale fra i vettori densità di corrente e campo elettrico. Tale studio riguarda la comparsa
di onde di banda laterale e la loro dipendenza dalle direzioni di polarizzazione delle onde interagenti.
Summary The influence of radio wave polarization on some nonlinear phenomena in the inosphere is studied through a new and more complete functional relation between current density and electric field vectors. This study is concerned with the occurrence of ?sideband? waves and their dependence on the polarization directions of interacting waves.相似文献
997.
A method for quantitative characterization of the noncrystalline region in poly(ethylene terephthalate) (PET) fibers based on x-ray wide-angle diffraction data is elaborated. The procedure consists in a computational resolution of the diffracted intensity into individual peaks for 010, 11 0, and 100 planes and into isotropic and anisotropic components of diffuse scattering. The results show that the content of mesomorphic regions in the noncrystalline part of PET fibers with draw ratio of λ = 3.0 varies from 12% to 32% depending on the temperature of heat treatment. 相似文献
998.
Laura Belvisi Gianpaolo Bravi Carlo Scolastico Anna Vulpetti Aldo Salimbeni Roberto Todeschini 《Journal of computer-aided molecular design》1994,8(2):211-220
Summary A 3D QSAR methodology based on the combined use of conformational analysis and chemometrics was applied to perform a comparative analysis of the 3D conformational features of 13 nonpeptide angiotensin II receptor antagonists showing different levels of binding affinity. Conformational analysis by using a molecular mechanics MM2 method was carried out for each of these structures to obtain conformational minima. These minima were described by ten interatomic distances which define the relative spatial disposition of five significant atoms belonging to relevant functional groups present in all the 13 molecules. The structure-activity relationship between the interatomic distances and the biological activity was then assessed by using chemometric methods (cluster analysis, principal component analysis, classification methods). With our indirect approach based on the search for geometrical similarity it was possible, even though structural information on the receptor active site was lacking, to identify the 3D geometrical requirements for the binding affinity of nonpeptide angiotensin II receptor inhibitors. 相似文献
999.
1000.
We report steady state fluorescence and lifetime emission studies of d(GGTTGGTGTGGTTGG) (TBA) and d(GGGTTAGGGTTAGGGTTAGGG)
(Htelom) oligonucleotides labeled with pyrene through a 3-aminopropyl linker. Such G-rich sequences are able to self-assemble
into G-quadruplexes, especially in the presence of specific cations like potassium. A comparative studies with single- and
double-labeled G-quadruplexes were carried out. For each probe we have measured fluorescence decays for emission wavelength
of 390 and 480 nm in the varying concentration of potassium ion. We have calculated average lifetimes <τ> for every system
as well as the fractional distribution αi of emitting species. 相似文献