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101.
102.
J. Fernndez Rico J. J. Fernndez I. Ema R. Lpez G. Ramírez 《International journal of quantum chemistry》2000,78(2):83-93
As a first application of the shift operators method we derive master formulas for the two‐ and three‐center one‐electron integrals involving Gaussians, Slater, and Bessel basis functions. All these formulas have a common structure consisting in linear combinations of polynomials of differences of nuclear coordinates. Whereas the polynomials are independent of the type (GTO, BTO, or STO) of basis functions, the coefficients depend on both the class of integral (overlap, kinetic energy, nuclear attraction) and the type of basis functions. We present the general expression of polynomials and coefficients as well as the recurrence relations for both the polynomials and the whole integrals. Finally, we remark on the formal and computational advantages of this approach. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 78: 83–93, 2000 相似文献
103.
C. Alvarez Ibarra M. S. Arias Perez F. Fernandez Gonzalez M. Rico Sarompas 《Magnetic resonance in chemistry : MRC》1977,10(1):251-254
Assignment of RR and RS configurations to 2,2,6,6-tetramethyl-5-phenyl-3-heptanol diastereomers has been carried out through an analysis of the observed values for vicinal coupling constants of both isomers and their conformational distribution. The latter was previously estimated from steric interaction energies between groups. Since the RR isomer is monoconformational its magnetic parameters can be used to carry out conformational analysis of related acyclic compounds. 相似文献
104.
P. Bednarczyk G. de Angelis P. Spolaore D. Ackermann J. Rico D. Bazzacco S. Lunardi L. Müller C. Rossi Alvarez F. Scarlassara G. F. Segato F. Soramel 《Zeitschrift für Physik A Hadrons and Nuclei》1993,346(4):325-326
The previously unknown nucleus118Cs has been identified through γ-γ and γ-recoil coincidences using the GASP γ-spectrometer and Recoil Mass Spectrometer. The level scheme constructed on the base of triple γ coincidences shows a collective structure based on the π?1g9/2?νh11/2 configuration. 相似文献
105.
V. VolkovM. Rico A. Méndez-BlasC. Zaldo 《Journal of Physics and Chemistry of Solids》2002,63(1):95-105
NaBi1−xREx(XO4)2, X=W or Mo and RE=Pr, Nd, Ho, Er and Yb single crystals have been grown by the Czochralski technique. Rare earth concentrations about 3.5×1020 cm−3 have been achieved in crystals with good optical quality. Melt stability is obtained by synthesising NaBi(XO4)2 from the precursor Na2X4O13 phase and minimising Mo volatility. The strength of W and Mo compounds to chemical attack and thermal annealing in several atmospheres is reported. Mo compound is etched by inorganic acids and becomes coloured after vacuum annealing. The optical absorption, photoluminescence and refractive indices of the hosts are characterised and show a dichroic character. The lattice disorder induces broadening of the 10 K optical absorption of the rare earth impurities. 相似文献
106.
Oxygen directed β-deprotonation of a vinyl ether leads to substituted enol ethers. The stereoselective elaboration to a naturally occuring 1,3-diol is described. 相似文献
107.
Santiveri CM Santoro J Rico M Jiménez MA 《Journal of the American Chemical Society》2002,124(50):14903-14909
The temperature dependence of the (1)H chemical shifts of six designed peptides previously shown to adopt beta-hairpin structures in aqueous solution has been analyzed in terms of two-state (beta-hairpin left arrow over right arrow coil) equilibrium. The stability of the beta-hairpins formed by these peptides, as derived from their T(m) (midpoint transition temperature) values, parallels in general their ability to adopt those structures as deduced from independent NMR parameters: NOEs, Deltadelta(C)(alpha)(H), Deltadelta(C)(alpha), and Deltadelta(C)(beta) values. The observed T(m) values are dependent on the particular position within the beta-hairpin that is probed, indicating that their folding to a beta-hairpin conformation deviates from a "true" two-state transition. To obtain individual T(m) values for each hairpin region in each peptide, a simplified model of a successive uncoupled two-state equilibrium covering the entire process has been applied. The distribution of T(m) values obtained for the different beta-hairpin regions (turn, strands, backbone, side chains) in the six analyzed peptides reveals a similar pattern. A model for beta-hairpin folding is proposed on the basis of this pattern and the reasonable assumption that regions showing higher T(m) values are the last ones to unfold and, presumably, the first to form. With this assumption, the analysis suggests that turn formation is the first event in beta-hairpin folding. This is consistent with previous results on the essential role of the turn sequence in beta-hairpin folding. 相似文献
108.
E. Glvez M. S. Arias B. Rico I. Ardid F. Florencio J. Sanz 《Journal of heterocyclic chemistry》1989,26(4):965-970
A series of 10α-acyloxy-N-phenethyl-8-azabicyclo[4.3.1]decane derivatives have been synthesized and studied by 1H and 13C nmr spectroscopy, and the crystal structure of N-phenethyl-10aL-(xanten-9″-carbonyloxy)bicyclo[4.3.1]decane 2 has been determined by X-ray diffraction. The compounds studied display in deuteriochloroform the same preferred conformation adopted by the piperidine ring as a distorted chair conformation flattened at N-8 with both the phenethyl and acyloxy groups in the equatorial position with respect to the piperidine ring. These results are in close agreement with that found for compound 2 in the crystalline state. 相似文献
109.
BrCF2CF2Br reacts easily with various potassium thiophenoxides and phenoxides to give respectively 2-bromo tetrafluoroethyl thioethers and ethers. The lipophilicity of C6H5SCF2CF2Br and C6H5OCF2CF2Br is measured and compared with that of the well known C6H5SCF2CF2H and C6H5OCF2CF2H. 相似文献
110.
By using the tripodal tetradentate ligand tris(2-benzimidazolylmethyl)amine (H(3)ntb), which can have several charge states depending on the number of secondary amine protons, mononuclear octahedral and dinuclear trigonal bipyramidal Fe(III) complexes were prepared. The reaction of mononuclear octahedral [Fe(III)(H(3)ntb)Cl(2)]ClO(4), 1, with 3 equiv of sec-butylamine in methanol led to the formation of mononuclear cis-dimethoxo octahedral Fe(III)(H(2)ntb)(OMe)(2), 2. One equivalent of the sec-butylamine was used to generate the monoanionic H(2)ntb(-) ligand where one of the three amines in the benzimidazolyl groups was deprotonated. The remaining 2 equiv were used to generate two methoxides that were coordinated to the octahedral Fe(III) ion in a cis fashion as demonstrated by the chlorides in 1. Reaction of 1 with excess (7 equiv) sec-butylamine generated the doubly deprotonated dianionic Hntb(2-) that stabilized the dinuclear mu-oxo Fe(III)(2)O(Hntb)(2), 3, adopting a five-coordinate trigonal bipyramidal geometry. The magnetic data for 3 are consistent with the antiferromagnetically coupled Fe(III) (S = 5/2) sites with the coupling constant J = -127 cm(-1). 相似文献