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Margarita Surez Esperanza Salfrn Estael Ochoa Yamila Verdecia Livan Alba Nazario Martín Carlos Seoane Roberto Martínez‐Alvarez Hector Novoa De Armas Norbert M. Blaton Oswald M. Peeters Camiel J. De Ranter 《Journal of heterocyclic chemistry》2003,40(2):269-275
Two dihydropyridines endowed with fluorine atoms ( 3 ) and fluorine and chlorine atoms ( 4 ) have been synthesized and structurally characterized by experimental X‐ray analyses and theoretical calculations at the semiempirical (AMI) and ab initio (HF/6–31G*) levels. The results show that these compounds meet the required criteria to act as potential calcium channel modulators. 相似文献
54.
Ray MS Ghosh A Das A Drew MG Ribas-Arino J Novoa J Ribas J 《Chemical communications (Cambridge, England)》2004,(9):1102-1103
[Cu(4)L(2)(bpy)(4)(H(2)O)(3)](ClO(4))(4).2.5H(2)O, 1, a new tetranuclear Cu(II) cluster showing square planar geometry, formed with aspartate bridging ligand (L) has been synthesized. The global magnetic coupling is ferromagnetic but theoretical DFT/B3LYP calculations are necessary to assign which Cu-L-Cu side is ferro or antiferromagnetically coupled. 相似文献
55.
Two different biodegradable latex polymers functionalised by hydroxy (1) or gluconamide (2) groups proved to be good immobilisation matrixes for glucose oxidase. The responses of these biosensors to glucose additions were measured by potentiostating the modified electrodes at 0.6 V/SCE in order to oxidise the hydrogen peroxide generated by the enzymatic oxidation of glucose in the presence of oxygen. The response of such electrodes was evaluated as a function of film thickness, pH and temperature. Rotating disk electrode experiments showed the influence of the enzyme on the structure of both latex films, namely a marked improvement in matrix permeability. The high permeability of the latex 1 based enzyme sensor (bilayer, P(m)=8.10x10(-4) cm s(-1)) resulted in a high dynamic range. Furthermore, the activation energy for a latex 1 sensor was determined to be 44.55 and 18.03 kJ mol(-1), respectively depending on the conformation of the enzyme. 相似文献
56.
Braga D D'Oria E Grepioni F Mota F Novoa JJ Rovira C 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(5):1173-1180
The O-H...O interaction formed by the anions HCO(3)(-) and CO(3)(2-) has been investigated on the basis of data retrieved from the Inorganic Crystal Structure Database (ICSD) and by means of ab initio computations. It has been shown that the O-H...O separations associated with HCO(3)(-)...(3)(2-) interactions are shorter than those found in crystals containing hydrogen carbonate monoanions such as HCO(3)(-)...HCO(3)(-). Ab initio MP2/6-311G++(2d,2p) computations on the crystal Na(3)(HCO(3))(CO(3)).2H(2)O have shown that the interaction between the monoanion donor and the dianion acceptor, for example HCO(3)(-)...CO(3)(2-), is more repulsive than that between singly charged ions, for example HCO(3)(-)...HCO(3)(-), but is largely overcompensated for by anion-cation electrostatic attractions. The shortening of the (-)O-H...O(2-) interaction relative to the (-)O-H...O(-) interaction has been explained as a consequence of the increased charge compression, that is of the stronger cation-anion interactions established by the CO(3)(2-) dianions with respect to those established by monoanions, and does not reflect an increase in the strength of the (-)O-H ...O(-) interaction. To expand the structural sample in the crystal packing analysis, the structure of the novel mixed salt K(2)Na(HCO(3))(CO(3)).2H(2)O has been determined by single-crystal X-ray diffraction and compared with the structure of the salt Na(3)(HCO(3))(CO(3)).2H(2)O used in the computations. 相似文献
57.
Ribas-Ariño J Curioni A Andreoni W Novoa JJ 《The journal of physical chemistry. A》2005,109(23):4979-4982
Bond breaking in C60-C60 dimeric units is believed to play an important role in the onset of magnetism in 2D polymeric C60. On the basis of density-functional theory, the calculations we present here provide further insight into this mechanism through a quantitative characterization of the bond-breaking processes in the isolated dumbbell-shaped C60 dimer. In particular, the analysis of the calculated potential energy surfaces for the low-lying singlet and triplet states identifies and locates the S0-T2 crossing point, which is crucial for the transition to a magnetic state to take place under thermal conditions. These results also suggest a possible new approach to the production of magnetic polymeric C60. 相似文献
58.
Héctor Novoa de Armas Norbert M. Blaton Oswald M. Peeters Camiel J. De Ranter Margarita Suárez Estael Ochoa Yamila Verdecia Esperanza Salfrán 《Journal of chemical crystallography》2000,30(3):189-194
The synthesis and structural characterization of two 5-Arylidene derivatives of Meldrum's acid (2,2-dimethyl-1,3-dioxane-4,6-dione) are described: 5-(4-Nitrobenciliden)-2,2-dimethyl-1,3-dioxane-4,6-dione (3a), and 5-(4-Methoxybenciliden)-2,2-dimethyl-1,3-dioxane-4,6-dione (3b). The structure of 3a was refined to R1 = 0.0421 for 2148 reflections (with I > 2 (I)). Crystal data for 3a: C13H11NO6, orthorhombic, space group Pbca, a = 16.008(3), b = 6.137(1), c = 25.281(5) Å, V = 2483.6(8) Å3, Z = 8. The structure of 3b was refined to R1 = 0.0496 for 4681 reflections (with I > 2(I)). Crystal data for 3b: C14H14O5, triclinic, space group P1, a = 9.131(2), b = 9.922(2), c = 14.490(3)Å, = 85.076(6), = 84.80(3), = 89.37(2)°,V = 1302.4(5) Å3, Z = 4. The results of crystallographic and molecular modeling (AM1) were compared. The molecules in the crystal are held together, in both compounds, by van der Waals forces and C—H···O hydrogen bond interactions. 相似文献
59.
Orientational Preference of Long,Multicenter Bonds in Radical Anion Dimers: A Case Study of π‐[TCNB]22− and π‐[TCNP]22− 下载免费PDF全文
Dr. Marçal Capdevila‐Cortada Prof. Joel S. Miller Prof. Juan J. Novoa 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(17):6420-6432
The similar shape and electronic structure of the radical anions of 1,2,4,5‐tetracyanopyrazine (TCNP) and 1,2,4,5‐tetracyanobenzene (TCNB) suggest a similar relative orientation for their long, multicenter carbon?carbon bond in π‐[TCNP]22? and in π‐[TCNB]22?, in good accord with the Maximin Principle predictions. Instead, the two known structures of π‐[TCNP]22? have a D2h(θ=0°) and a C2(θ=30°) orientation (θ being the dihedral angle that determines the rotation of one radical anion relative to the other along the axis that passes through center of the two six‐membered rings). The only known π‐[TCNB]22? structure has a C2(θ=60°) orientation. The origin of these preferences was investigated for both dimers by computing (at the RASPT2/RASSCF(30,28) level) the variation with θ of the interaction energy (Eint) and the variation of the Eint components. It was found that: 1) a long, multicenter bond exists for all orientations; 2) the Eint(θ) angular dependence is similar in both dimers; 3) for all orientations the electrostatic component dominates the value of Eint(θ), although the dispersion and bonding components also play a relevant role; and 4) the Maximin Principle curve reproduces well the shape of the Eint(θ) curve for isolated dimers, although none of them reproduce the experimental preferences. Only after the (radical anion).? ??? cation+ interactions are also included in the model aggregate are the experimental data reproduced computationally. 相似文献
60.
Inside Back Cover: Orientational Preference of Long,Multicenter Bonds in Radical Anion Dimers: A Case Study of π‐[TCNB]22− and π‐[TCNP]22− (Chem. Eur. J. 17/2015) 下载免费PDF全文