Crystal structure of pyridinium 1,1 '-bis(4-hydroxy-pyrimid-6-on-2-thion-5-yl)-1 ''-(4-nitrophenyl)methane methanol solvate monohydrate, (C5H6N)(C15H10N5O6S2)center dot CH3OH center dot H2O

C21H22N6O8S2, monoclinic, P12(1)/n1 (no. 14), a = 10.1931(8) angstrom, b = 11.9627(7) angstrom, c = 20.299(2) angstrom, beta = 95.131(4)degrees, V = 2465.2 A(3), Z = 4, R-gt(F) = 0.079, wR(ref)(F-2) = 0.229, T = 100 K.

Bis(trifluoromethyl)mercury(II) complexes with purine and 3,5-dimethyl-4 '-amino-triazole as ligands, [Hg(CF3)(2)(Pur)](4) and [Hg(CF3)(2)(Dat)](2)

Colourless single crystals of [Hg(CF3)(2)(Pur)](4) and [Hg(CF3)(2)(Dat)](2) were obtained from aqueous and etheric solutions of the respective components Purine, (imidazo[4,5-d]pyrimidine, Pur), 3,5-dimethyl-4 '-amino-triazole (Dat) and bis(trifluoromethyl)mercury(II), Hg(CF3)(2). [Hg(CF3)(2)(Pur)](4) crystallizes with the tetragonal system (P-4, Z = 8, a = 1486.8(2), c = 1026.2(l) pm, R-all = 0.0657) with tetrameric molecules consisting of four purine molecules bridged by slightly bent Hg(CF3)2 molecules forming a cage with the CF3 ligands surrounding this cage. The two modifications of [Hg(Dat)(CF3)2]2 (1: 170 K, triclinic, P-1, Z = 2, a 814.9(2), b = 845.4(2), c = 968.4(3) pm, alpha = 106.55(2)degrees, beta= 103.41(2)degrees, gamma = 110.79(2)degrees, R-all = 0.1189; II: monoclinic, P2(1)/c, Z = 8, a = 879.8(2), b = 1731.0(3), c = 1593.9(3) pm, beta = 106.89(2)degrees, R-all = 0.1199) both contain dimeric molecules that are stacked parallel to one crystal axis to strands which are arranged in a parallel fashion in I and rotated against each other in 11 by 110 degrees. In both, the tetrameric [Hg(CF3)(2)(Pur)](4) and the dimeric [Hg(CF3)(2)(Dat)](2) the Hg(CF3)(2) molecules are slightly bent (around 167 and 170 degrees) and rather weakly attached to the N-donor ligands Pur and Dat with Hg-N distances around 272 pm, although in both cases the Hg atoms bridge between two ligand molecules.

Bis(tetrabutylammonium) decaiodotetramercurate(II), (Bu4N)(2)[Hg4I10]

Bu4N)(2)[Hg4I10] is the first compound for which tetranuclear anions [Hg4I10](2-) are observed in its crystal structure. Charge balance is achieved by ordered [Bu4N](+) cations.

Bis-guanylhydrazone diimidazo[1,2-a:1,2-c]pyrimidine as a novel and specific G-quadruplex binding motif

A bis-guanylhydrazone derivative of diimidazo[1,2-a:1,2-c]pyrimidine has unexpectedly been found to be a potent stabiliser of several quadruplex DNAs, whereas there is no significant interaction with duplex DNA. Molecular modeling suggests that the guanylhydrazone groups play an active role in quadruplex binding.

Volumetric properties and enthalpies of solution of alcohols CkH2k+1OH (k = 1, 2, 6) in 1-methyl-3-alkylimidazolium bis(trifluoromethylsulfonyl)imide {[C1CnIm][NTf2] n = 2, 4, 6, 8, 10} ionic liquids

We present a study on the effect of the alkyl chain length of the imidazolium ring in 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquids, [C1CnIm][NTf2] (n = 2 to 10), on the mixing properties of (ionic liquid + alcohol) mixtures (enthalpy and volume). We have measured small excess molar volumes with highly asymmetric curves as a function of mole fraction composition (S-shape) with more negative values in the alcohol-rich regions. The excess molar volumes increase with the increase of the alkyl-chain length of the imidazolium cation of the ionic liquid. The values of the partial molar excess enthalpy and the enthalpy of mixing are positive and, for the case of methanol, do not vary monotonously with the length of the alkyl side-chain of the cation on the ionic liquid – increasing from n = 2 to 6 and then decreasing from n = 8. This non-monotonous variation is explained by a more favourable interaction of methanol with the cation head group of the ionic liquid for alkyl chains longer than eight carbon atoms. It is also observed that the mixing is less favourable for the smaller alcohols, the enthalpy of mixing decreasing to less positive values as the alkyl chain of the alcohol increases. Based on the data from this work and on the knowledge of the vapour pressure of {[C1CnIm][NTf2] + alcohol} binary mixtures at T = 298 K reported in the literature, the excess Gibbs free energy, excess enthalpy and excess entropy could be then calculated and it was observed that these mixtures behave like the ones constituted by a non-associating and a non-polar component, with its solution behaviour being determined by the enthalpy.

Triply-bridged diphos disilver helical complexes [Ag-2(mu(2)-dppa-P,P')(3)(anion)(2)] [dppa = bis(diphenylphosphino)acetylene]

Triply-bridged disilver complexes [Ag-2(mu(2)-dppa-P,P')(3)(anion)(2)] form selectively and are stabilised by many aromatic interactions.

The first structural characterization of a [2.2]PHANEPHOS - Transition-metal complex: Structure of rac-[Pd(4,12-bis(diphenylphosphino)[2.2]paracyclophane)Cl-2]

The solid-state structure of the [2.2]PHANEPHOS-transition-metal complex rac-[Pd(4,12-bis(diphenylphosphino)[2.2]paracyclophane)Cl-2] has been established by single-crystal X-ray diffraction. The P-Pd-P bite angle is ideally suited to catalytic processes such as carbon-carbon cross-coupling reactions, which involve reductive elimination as the rate-determining step.

Platinum bis-acetylide complexes with the 4,4'-dimethyl-2,2'-bipyridyl ligand

[Pt(Me(2)bipy)Cl-2](Me(2)bipy = 4,4'-dimethyl-2,2'-bipyridine) and HC=CC6H4-4-R react in the presence of diisopropylamine and CuI as catalyst to give the platinum bis-acetylides [Pt(Me(2)bipy)(C=CC6H4-4-R)(2)] R = H, Me, NO2. Initial spectroscopic, electrochemical and reactivity studies are presented. (C) 1997 Elsevier Science S.A.

Influence of the cation on the solubility of CO2 and H 2 in ionic liquids based on the bis(trifluoromethylsulfonyl)imide anion

Experimental values for the solubility of carbon dioxide and hydrogen in three room temperature ionic liquids based on the same anion- (bistrifluoromethylsulfonyl)imide [Ntf2]-and three different cations-1-butyl-3-methylimidazolium, [C4mim], 1-ethyl-3- methylimidazolium, [C2mim] and trimethyl-butylammonium, [N 4111]-are reported between 283 and 343 K and close to atmospheric pressure. Carbon dioxide, with a mole-fraction solubility of the order of 10-2, is two orders of magnitude more soluble than hydrogen. The solubility of CO2 is very similar in the three ionic liquids although slightly lower in the presence of the [C2mim] cation. In the case of H2, noticeable differences were observed with larger mole fraction solubilities in the presence of [N4111] followed by [C 4mim]. All of the mole-fraction solubilities decrease with increasing temperature. From the variation of Henry's law constants with temperature, the thermodynamic functions of solvation were calculated. The precision of the experimental data, considered as the average absolute deviation of the Henry's law constants from appropriate smoothing equations, is always better than ±1%. © Springer Science+Business Media, LLC 2007.

mu-pyrazine-kappa N-2 : N '-bis[diiodomercury(II)]

In [Hg2I4(Pyp)] (Pyp = pyrazine, C4H4N2), centrosymmetric molecules consist of two HgI2 units connected by a pyrazine molecule.

Bis(tetraethylammonium) decachloro-tetramercurate(II), (Et4N)(2)[Hg4Cl10]

The structure of (Et4N)(2)[Hg4Cl10] contains dinuclear [Hg2Cl6](2-) anions and HgCl2 molecules, with definite interactions so that the anion can also be formulated as [Hg4Cl10](2-). Alternatively the compound can be written as (Et4N)(2)[Hg2Cl6][HgCl2](2). Charge balance is achieved by ordered [Et4N](+) cations. An inversion centre is situated at the centre of the [Hg2Cl6](2-) anions.

Bis(tetraethylammonium) di-mu-bromo-bis[dibromomercurate(II)], (Et4N)(2)[Hg2Br6]

The structure of (Et4N)(2)[Hg2Br6] contains dinuclear [Hg2Br6](2-) species as isolated anions. Charge balance is achieved by ordered [Et4N](+) cations. An inversion centre is located at the centre of the [Hg2Br6](2-) unit.

Bis(tetraethylammonium) octabromo-trimercurate(II), (Et4N)(2)[Hg3Br8]

The structure of (Et4N)(2)[Hg3Br8] contains isolated dinuclear [Hg2Br6](2-) anions and neutral HgBr2 molecules. Charge balance is achieved by ordered [Et4N](+) cations. The formula may therefore be written as (Et4N)(2)[Hg2Br6][HgBr2]. The N atoms of the (Et4N)(+) ions lie on a (4) over bar axis along [001] and, whereas one of the mercury(II) ions is placed on a mirror plane perpendicular to the c axis, the second one is located on a special position of site symmetry 2/m.

The solution structure of 1:2 phenol/N-methylpyridinium bis{(trifluoromethyl)sulfonyl}imide liquid mixtures

Neutron diffraction has been used to investigate the liquid structure of a 1:2 solution of phenol in the ionic liquid N-methylpyridinium bis{(trifluoromethyl)sulfonyl}imide at 60 ◦C, using the empirical potential structure refinement (EPSR) process to model the data obtained from the SANDALS diffractometer at ISIS. Addition of phenol results in suppression of the melting point of the pyridinium salt and formation of a room temperature solution with aromatic phenol–cation and phenol-OH to anion hydrogen-bonding interactions.

Estudio del (2-(Bis-(N-acetilsulfanililimino) -4 Tiazolina

Tesis (Maestría en Ciencias con Especialidad en Química Orgánica) UANL