La bencidrilamina (BB2) y sus derivados obtenidos por sustitución arílica y/o amínica presentan actividad inhibidora de los espasmos de la musculatura lisa. Como punto de partida de una investigación cuya finalidad es el diseño de nuevos derivados con mayor actividad y especificidad se estudió, mediante difracción de rayos X de monocristal, la geometría de la bencidrilamina en su forma de clorhidrato, encontrándose que presenta una conformación helicoidal, con los anillos aproximadamente perpendiculares entre sí. Cálculos de mecánica molecular para la molécula libre de bencidrilamina y de su forma protonada (bencidrilamonio), utilizando distintos potenciales, muestran que la conformación de energía mínima depende de la inclusión o no de las interacciones coulombianas. Puesto que el estado relevante para la función biológica es en solución acuosa, se efectuaron cálculos de energía mínima en presencia de agua y se comenzó el análisis mediante dinámica molecular. La simulación se lleva a cabo a presión y temperatura constante en una caja cúbica en presencia de 216 moléculas de agua (SPC/E). Se discute la relación entre la geometría en el estado sólido y las geometrías predichas para la molécula libre y solvatada.

The synthesis, an improved refined crystal and molecular structure re-determination, and the thermal decomposition behavior of two Zn(II) derivatives of isocinchomeronic acid (2,5-pyridinedicarboxylic acid or H 2 2,5-pydc) are presented. [Zn(2,5-pydc)(H 2 O) 3 Zn(2,5-pydc)(H 2 O) 2 ] 2 ( 1 ) crystallizes in the triclinic P-1 space group with a = 7.106(2), b = 11.450(2), c = 11.869(1) Å, α = 107.29(1), β = 104.08(1), γ = 90.32(2)°, and Z = 2. [Zn(2,5-pydc)(H 2 O) 2 ] · H 2 O ( 2 ) is orthorhombic (P2 1 2 1 2 1 space group), with a = 7.342(1), b = 9.430(1), c = 13.834(2) Å, and Z = 4. The structures were refined to agreement R 1 -factors of 0.0315 ( 1 ) and 0.0336 ( 2 ). Complex ( 1 ) is arranged as molecular Zn 4 (2,5-pydc) 4 (H 2 O) 10 tetramers, the cages of which define channels that remain unblocked by anions. Compound ( 2 ) is polymeric with Zn(2,5-pydc)(H 2 O) 2 and Zn(2,5-pydc)(H 2 O) 3 units linked through bridging ligands. Both compounds were synthesized under mild conditions in aqueous media, without need to resort to hydrothermal media. Changing the pH from 4.51 to 5.75 suffices to direct the chemical processes toward the orthorhombic compound rather than to the triclinic one.

The synthesis and characterisation by solid-state 111Cd NMR of Cd(2,3-), Cd(2,4-), Cd(2,5-) and Cd(2,6-pyridinedicarboxylato)·xH2O is reported. Results indicate that the 111Cd NMR signal is very sensitive to the relative position of both carboxylates. Similar shifts (at 54.0 and 55.4ppm) are found for the 2,4- and the 2,6-isomers where the carboxylates groups are meta to each other. For the 2,3- and 2,5-derivatives (carboxylates in ortho and para positions), the signals are detected at 119.6 and 84.2ppm. The crystal and molecular structure of the seven-coordinated cadmium complex, [Cd(2,4-pyridinedicarboxylato)(H2O)3]·1/2H2O is also reported. This data allows a correlation between Cd–O and Cd–N coordination and geometry with 111Cd chemical shifts. Additional coupling between 111Cd and 14N in 2,3- (also found in 2,4-pydc) suggests only one N is coordinated to Cd. The anisotropy magnitude, Δσ, and the asymmetry parameter, η, are also analysed.

The synthesis and the crystal and molecular structures of three metal(II) derivatives of lutidinic acid are presented (lutidinic acid=2,4-pyridinedicarboxylic acid=H22,4-pydc). Zn(2,4-pydc)(H2O)4]·H2O crystallizes in the monoclinic space group P21/c, with a=7.764(3), b=6.546(3), c=22.021(8)Å; β=91.45(4)°; and Z=4. Na2[Zn(2,4-pydc)2(H2O)2]·8H2O crystallizes in P21/a, with a=7.070(2), b=13.630(2), c=12.520(1)Å; β=91.66(1)°; and Z=2. [Ni(H2O)6][Ni(2,4-pydc)2(H2O)2] crystallizes in the triclinic space group P−1, with a=5.200(7), b=7.890(3), c=13.872(5)Å; α=84.96(3), β=85.64(2)°, γ=73.21(4); and Z=2. The Zn and Ni ions are hexacoordinated and the lutidinate group is almost planar binding the metal through an oxygen atom from the 2-carboxylate group. All compounds present a dangling uncoordinated 4-carboxylate group. The stereochemistry of the title compounds is compared with other metal (II) pyridinedicarboxylates.

The disproportionation reaction kinetics of tin monoxide at 723 K was studied by Mössbauer spectroscopy. The kinetic parameters of the reaction were obtained by objective data processing of the Mössbauer spectra, treating the data matrix with the Single Value Decomposition procedure that, in addition, yields the spectrum of the intermediate oxide. The procedure was applied on the assumptions that the f-factors of Sn(II) and Sn(IV) atoms belonging to the intermediate oxide are equal to those of Sn(II) and Sn(IV) atoms of SnO and SnO2, respectively, that the stoichiometry of the intermediate oxide is Sn3O4, and that the disproportionation proceeds by a set of two successive first order reactions described by the sequence SnO→intermediate oxide→SnO2. The kinetic rate constants obtained for the first and second reactions were k1=2.47×10−4 s−1 and k2=1.13×10−5 s−1, respectively. The time-profile of the mole fraction of each component in partially reacted samples shows that at 723 K, the intermediate accumulates in the time bracket between ca. 100–1000 min.

The first crystal structure of a simple metal(II) derivative of pyridine-2,4-dicarboxylic acid (lutidinic acid) is reported. The title compound crystallises in the monoclinic space group P2(1)/a, with a=12.968(5), b=8.3152(9), c=16.004(2) Angstrom, beta=103.36(2)degrees, Z=4. The structure was solved employing 2484 independent X-ray reflections with I>2 sigma(I) by Patterson and Fourier methods and refined by full-matrix least-squares to R-1=0.074. The Cu-II ion is located in a pyramidal environment coordinating to two nitrogen atoms and two oxygen atoms from the lutidinate ligands; the apical position in the pyramid is occupied by a water group. The stereochemistry of the title compound is compared with that of other copper(II) pyridinedicarboxylates. Its thermal behaviour is also presented.

As a basis for the description of dehydration mechanisms, the molecular structures of two copper(II) dipicolinates, Cu(dipic).2H2O (triclinic) and Cu(dipic).3H2O, are presented and compared with those of other copper(II) dipicolinates. The kinetics of the isothermal dehydration of the monoclinic and triclinic polymorphs of Cu(dipic).2H2O were measured. The monoclinic variety dehydrates in a two-step process; a linear α/t relationship is found for the first step and a two-dimensional diffusion-controlled reaction (D2) law ((1 − α)ln(1 − α) + a = kt) for the second. Triclinic Cu(dipic).2H2O dehydrates in a one-step process. The relation between α and time is linear at lower temperatures but gradually changes to an Avrami-Erofe'ev (A2) model (− ln (1 − α)1/n = kt) at higher temperatures. A qualitative model based on optical microscopic observations, structural determinations and thermogravimetric data is proposed. The general relationship between dehydration behavior and structure in this series of compounds is discussed.

The molecular structure of a new copper dipicolinate, Cu(dipic)(H2dipic)·H2O, and a refinement of the previously reported Cu(dipic)(H2dipic)·3H2O are presented. The Jahn-Teller effect, as operative in six-coordinated CuII surrounded by two planar tridentate ligands, is responsible for the presence of a dianion and a neutral acid molecule in the structure. As opposed to previously reported copper dipicolinates, water molecules do not coordinate and in the trihydrate dehydration is facile because interstital water finds easy dehydration pathways; the mechanism involves nucleation and fast bidimensional growth. The monohydrate, however, presents tightly bound (through hydrogen bonds) water and no easy dehydration pathways are available; the dehydration mechanism involves fluid-flux nucleation, mediated by fusion. Five different copper(II) dipicolinates are known; because of the strong tendency of this ligand to form tridentate mononuclear complexes, all of them, except monoclinic Cu(dipic)·2H2O, belong to the class of molecular solids. In the monoclinic dihydrate, carbonyl O atoms are involved in defining chains that run parallel to [001] planes.

The experimental results of the title reaction were modeled as a nucleation and growth process. Nucleation is restricted to the lateral faces of the platelets of the parent hydrate (space group Cc), and growth is anisotropic, two rate constants (for lateral and normal growth) being introduced. The results are compared with the empirical description given by Avrami's equation, and shown to rationalize the data adequately. In particular, the influence of water vapor pressure is discussed.

Sodium pentacyanonitrosylosmate(II) dihydrate, Na-2[Os(CN)(5)NO].2H(2)O, was synthesized by photolyzing a mixture of hexacyanoosmate(II) and nitrite ion, with further purification through ion-exchange and precipitation techniques. The compound is isostructural with the iron and ruthenium analogue species. The crystals are orthorhombic (Pnnm) with a = 6.312 (1) Angstrom, b = 12.090 (2) Angstrom, c = 15.828 (3) Angstrom, and Z = 4. Relevant lengths and angles within the distorted anion octahedra are compared for the three (Fe, Ru, Os) compounds. IR and UV-visible spectral data are also comparatively discussed. The results are indicative of a very strong sigma-, as well as back-bonding pi-interaction from Os toward nitrosyl and cyanides. The complex is electrophilically reactive toward several bases such as OH-, SH- and N2H4. With OH-, an equilibrium reaction is established, [Os(CN)(5)NO](2-) + 2OH(-) reversible arrow [Os(CN)(5)NO2](4-) + H2O, with K = 42 +/- 1 M(-2) (I = 1 M, 25.0 degrees C). From the kinetic and mechanistic analysis, k(obs) = 1.37 x 10(-4) M(-1) s(-1), is determined by the rate of nucleophilic attack of OH- into [Os(CN)(5)NO](2-) in the elementary step. Kinetic and equilibrium results are compared with those obtained for iron and ruthenium pentacyanonitrosyl analogues, as well as for other nitrosyl complexes containing ruthenium and osmium; thus, the different factors influencing nucleophilic rates and affinities are discussed, namely charge, radius and polarizability of the reactants, as well as the energy of the pi*(NO) level. The reactions of [Os(CN)(5)NO](2-) with other nucleophiles proceed through initial adduct formation and further decomposition.

The crystal and molecular structures of a series of salts formed by copper (II) with dipicolinic acid were used to interpret the dehydration behavior. The morphology of single crystals dehydration of Cu(dipic)·2H2O (monoclinic and triclinic symmetry), Cu(dipic)·3H2O and Cu(dipic) (H2dipic)·xH2O was shown to be governed by the arrangement of water molecules along specific orientations.

The dehydration behavior of copper(ii) bis(hydrogen o-phthalate)dihydrate is interpreted in terms of its crystal structure. Single crystal XRD data were used to derive important structural parameters. The TD of the anhydrous salt is also discussed in terms of proton transfer between adjacent anions.

The crystal structure of barium nitroprusside trihydrate, Ba[Fe(CN)5NO · 3H2O, at 140 K temperature and its differences with the room-temperature structure are reported. It has been determined using neutron diffraction data [F(000) = 418fm, Dx = 2.13g cm−3, μ = 0.6 cm−1 (evaluated), space group Pca21 (29), orthorhombic, Z = 4, a = 18.933(16), b = 7.646(8), c = 8.640(7)Å,V = 1250(4)Å3. A finalR-factor of 0.049 was obtained using 1094 observed structure factors. A rearrangement of water molecules occurs at the 233-K phase transition involving the loss of the symmetrym of the space group Pcam of the high-temperature structure with a rotation of 6.5° of the nitroprusside ion around the [1 0 0] direction. A positional disorder is found for only one water molecule. Possible hydrogen bonds are analyzed.

The crystal structures of sodium hexacyanoosmate, ruthenate and ferrate decahydrates, Na4M(CN)6·10H2O(M=Os, Ru, Fe), have been determined from X-ray diffraction data and refined by full matrix least-squares to final agreement values: R = 0.038, Rw = 0.039; R = 0.026, Rw = 0.041; R = 0.060, Rw = 0.043 for Os, Ru and Fe compounds, respectively. The compounds are isostructural and crystallize in the monoclinic space group P21/n, Z = 2, with a = 9.154, b = 11.506, c = 9.876 Å, β = 97.95°; a = 9.146, b = 11.486, c = 9.867 Å, β = 98.00°; a = 9.038, b = 11.450, c = 9.782 Å, β = 97.57°, for Os, Ru and Fe compounds, respectively. The structure can be described as layers of hexacyanometallate anions, intercalated with layers of sodium polyhedra containing hydration water molecules and N atoms, perpendicular to the crystallographic ac plane. MetalC and CN distances for the hexacyanide anions are correlated with those from other structurally related moieties. The infrared spectra of the compounds are complementary with previous results for potassium salts.

The crystal structure of hydrated nitroprussic acid was determined from X-ray diffraction data, showing that this compound should be formulated as oxonium nitroprusside monohydrate, (H3O)2[Fe(CN)5NO]·H2O. It crystallizes in the monoclinic space group P21, with a = 6.327(4) Å, b = 11.214(3) Å, c = 8.471(4) Å, β = 83.12(6)°, Z = 2. An antiparallel arrangement of NO groups, characteristic of several nitroprussides, is not observed in this case. One oxonium ion is hydrogen bonded to the water molecule, the bonding hydrogen atom being asymmetrically located between the oxygen atoms. This fact is reflected in the IR spectrum, which also shows the crystatlographic asymmetry of the water molecule in partially deuterated material. An assignment of all the features of the IR spectra is also presented.

Mathematical equations are derived that relate the extent of reaction α to time for the case of a reaction starting through surface nucleation and proceeding inwards and laterally through two growth-rate constants. The model is based in Avrami's theorem, and may therefore be considered as a modified Avrami model. The relation between −In(1−α) and time involves first-order Bessel functions Y1[2ωμ(t)] and J1[2ωμ(t)], where μ(t)=exp(−knt2) and ω2,=σδ0k1kn−1, ω is one of the model basic parameters. The final equations may be solved analytically under certain conditions, and numerically in the more general cases.

The crystal structure of cesium nitroprusside, Cs2[Fe(CN)5NO], has been determined from X-ray diffraction data and refined by full matrix least-squares to final values R = 0.043 and Rw = 0.065, for 4323 unique reflections. The substance crystallizes in the monoclinic space group P21n, with a = 9.589(3), b = 17.154(3), c = 14.583(6) Å, β = 99.89(5)°, Z = 8. Two inequivalent nitroprusside anions were found per asymmetric unit; this is in accordance with the infrared spectrum, which shows a duplication of several expected bands. An explanation is suggested for this last observation, based on the interaction of CN groups with the nearest cations.

Le compose du titre cristallise dans le systeme orthorhombique, groupe d'espace Cmma et sa structure est affinee jusqu'a R=0,0331

The molecular structure of 2,4,5-trichlorobenzenesulfonyl chloride has been determined by X-ray diffraction methods. The compound is orthorhombic,Aba2, witha=16.253(12),b=17.016(9),c=7.146(5) Å,V=1976(5) Å3,Z=8,D=1.88 kg·mm−3, (MoKα)=0.7107 Å,μ=136.8 cm−1,F(000)=1104. Data were obtained at room temperature; the finalR is 0.029 for 854 independent reflections. The substituted benzene ring is planar within experimental accuracy, the dihedral angle with the C(1)-S(1)-Cl(1) plane being 66.0(5)°. The compound has normal bond lengths and angles; some short intramolecular distances account for the maintenance of the rigid benzene frame. No significatively short intermolecular distances have been found. Confirmation of the oscillatory character of the semiexternal molecular motions operating above 180 K is accounted for.