Improved solvent formulations for efficient CO2 absorption and low-temperature desorption.

This experimental study describes efficient CO2 capture by 2-amino-2-methyl-1-propanol (AMP)/piperazine (PZ) in ethylene glycol monoethyl ether (EGMEE, 2-ethoxyethanol) containing approximately 15 wt % of water. In these experiments, the solvent is continuously circulated between the absorber (packed-bed reactor at 30, 40, or 45 °C) and the desorber (at 80, 85, or 90 °C). The CO2 -solvent reaction equilibria have been investigated by using ¹³C NMR spectroscopy, which provides confirmatory evidence that the formation of mono- and biscarbamate derivatives of PZ accounts for most of the CO2 absorbed by the AMP/PZ/EGMEE/H2O blend. The solid-state structures of AMP carbamate and of the carbonate salt of protonated AMP have been determined by using XRD. Both AMPCO2(-) and CO(3)(2-) species completely convert to the monoalkyl carbonates on dissolving the respective salts in methanol, ethanol, or ethylene glycol.

1,5,9,13-Tetraselena[13]ferrocenophane: synthesis, complexation, crystallographic and electrochemical study.

A novel macrocyclic ferrocenophane, 1,5,9,13-tetraselena[13]ferrocenophane (L), was synthesized. Reaction of L with [M(NCMe)(4)](PF(6))(2) (M = Pd and Pt) or [Cu(NCMe)(4)](PF(6)) led to complexes [ML](PF(6))(2) (M = Pd and Pt) or [CuL](PF(6)). The Ag(i) cation induced the formation of a one-dimensional polymer {[AgL](PF(6))}(n) due to its large ionic radius. The structures of L and its four complexes have been determined by X-ray crystallography. Electrochemical studies showed that, in [ML](PF(6))(2) (M = Pd and Pt), the half-wave potential of the 1,1'-ferrocenediyl group shifts to much more positive potentials due to the strong through-space interaction between the two metals (M...Fe).

Synthesis, characterisation and photochemistry of platinum diselenolenes.

The reaction between [Pt(PPh(3))(4)] and cycloocteno-1,2,3-selenadiazole or bis-cycloocteno-1,4-diselenin in toluene under reflux yielded the poorly soluble mononuclear platinum diselenolene [Pt(Se(2)C(8)H(12))(PPh(3))(2)], 1c. Treatment of [Pt(C(2)H(4))(PR(3))(2)] with a bis-cycloalkeno-1,4-diselenin in a mixture of 1,4-dioxane, THF and toluene under reflux led in good yield to the platinum diselenolenes [Pt(Se(2)C(n+4)H(2n+4))(PR(3))(2)] (R = Et (2), Bu (3); n = 3 (b), 4 (c)). The analogous complexes [Pt(Se(2)C(8)H(12))(L)] (L = dppm: 4c; L = dppe: 5c; L = dppp: 6c) were prepared from 1c via ligand exchange with chelating phosphines. All new compounds have been characterised by multinuclear NMR, IR and UV-visible spectroscopy and mass spectrometry, and their luminescence properties have been examined. The molecular structures of [Pt(Se(2)C(7)H(10))(PEt(3))(2)] (2b), [Pt(Se(2)C(8)H(12))(PEt(3))(2)] (2c) and [Pt(Se(2)C(8)H(12))(dppm)] (4c) have been determined by X-ray crystallography.

4-Amino-N-(3-meth-oxy-pyrazin-2-yl)benzene-sulfonamide.

The overall mol-ecular geometry of the title compound, C(11)H(12)N(4)O(3)S, is bent, with a dihedral angle of 89.24 (5)° between the best planes through the two aromatic rings. Each mol-ecule behaves as a hydrogen-bond donor toward three different mol-ecules, through its amidic and the two aminic H atoms, and it behaves as a hydrogen-bond acceptor from two other mol-ecules via one of its sulfonamidic O atoms. In the crystal, mol-ecules linked by N-H⋯N and N-H⋯O hydrogen bonds form kinked layers parallel to (001), adjacent layers being connected by van der Waals inter-actions.

Properly substituted 1,4-dioxane nucleus favours the selective M3 muscarinic receptor activation.

Novel analogues of cis-N,N,N-trimethyl-(6-methyl-1,4-dioxan-2-yl)methanaminium iodide (2a) were synthesized by inserting methyl groups alternatively or simultaneously in positions 5 and 6 of the 1,4-dioxane nucleus in all combinations. Their biological profile was assessed by receptor binding assays at human muscarinic M(1)-M(5) receptors stably expressed in CHO cells and by functional studies performed on classical isolated organ preparations, namely, rabbit electrically stimulated vas deferens, and guinea pig electrically stimulated left atrium, ileum, and lung strips. The results showed that the simultaneous presence of one methyl group in both positions 5 and 6 with a trans stereochemical relationship with each other (diastereomers 4 and 5) or the geminal dimethylation in position 6 (compound 8) favour the selective activation of M(3) receptors. Compounds 4, 5, and 8 might be valuable tools in the characterization of the M(3) receptor, as well as provide useful information for the design and development of novel selective M(3) antagonists.

Physico-chemical and structural characterization of diacerhein.

The physico-chemical and structural characterization of diacerhein, an anthraquinone with antiinflammatory activity, employed in the symptomatic treatment of inflammatory osteoarthritis, is reported. The combined use of FT-IR, DSC, X-ray powder and single-crystal diffraction has provided a valuable tool to fully characterize the title compound. The X-ray diffraction study has revealed the existence of hydrogen-bond assisted tight packing of the quasi-planar molecules in the solid. The collected results are intended to implement the information required for the compilation of drug master files.

Getting a clue to the hydrolytic activation of white phosphorus: the generation and stabilization of P(OH)2PHPHPH(OH) at ruthenium centers.

The bimetallic compound [{CpRu(PPh(3))(2)}(2)(mu,eta(1:1)-P(4))][CF(3)SO(3)](2), in which the tetrahedral P(4) is bound to two CpRu(PPh(3))(2) fragments, slowly reacts under mild conditions with a moderate excess of water (1:20) to yield a mixture of compounds. Among the hydrolysis products, the new, remarkably stable complexes [{CpRu(PPh(3))}{CpRu(PPh(3))(2)}{mu(1,4:3),eta(2:1)-P(OH)(2)PHPHPH(OH)}](CF(3)SO(3))(2) (2) and [{CpRu(PPh(3))(2)}{CpRu(PPh(3)){P(OH)(3))}(mu,eta(1:1)-P(2)H(4))](CF(3)SO(3))(2) (3) have been isolated. In the former, the previously unknown 1,1,4-tris(hydroxy)tetraphosphane molecule, P(OH)(2)PHPHPH(OH), is 1,4- and, respectively, 3-coordinated to the CpRu(PPh(3)) and the CpRu(PPh(3))(2) moieties; in the latter, the diphosphane P(2)H(4) is stabilized through coordination to two different metal fragments. All of the compounds were characterized by elemental analyses and IR and NMR spectroscopy. The crystal structure of 2 was determined by X-ray analysis. The formation of the hydroxytetraphosphane, containing the tetraphosphorus entity, provides a clue to the hydrolytic activation of the P(4) molecule.

{2-Hydr-oxy-3-[4-(2-methoxy-ethyl)-phen-oxy]prop-yl}isopropyl-ammonium hemisuccinate.

Metoprolol, a widely used adrenoreceptor blocking drug, is commonly administered as the succinate or tartrate salt. The structure of metoprolol succinate, C(15)H(26)NO(3) (+)·0.5C(4)H(4)O(4) (2-), is characterized by the presence of ribbons in which cations, generated by N-protonation of the metoprolol mol-ecules, are hydrogen bonded to succinate anions. The dicarboxylic acid transfers its H atoms to two metoprolol mol-ecules; the asymmetric unit contains one cation and half an anion, the latter possessing twofold rotational symmetry. There are localized nets of O-H⋯O and N-H⋯O hydrogen bonds along a ribbon, within centrosymmetric arrangements formed by pairs of metoprolol cations and pairs of anions, each of the latter contributing with one of its carboxyl groups to the localized net. This arrangement is repeated along the ribbon by the operation of the twofold axis bis-ecting the anion, as well as by the lattice translation.

4-(3-Methyl-anilino)-N-[N-(1-methyl-ethyl)carbamo-yl]pyridinium-3-sulfon-amidate (torasemide T-N): a low temperature redetermination.

The structure [Danilovski et al. (2001 ▶). Croat. Chim. Acta74, 103-120] of the T-N (non-solvated) polymorph of torasemide, C(16)H(20)N(4)O(3)S, a diuretic drug used in the treatment of hypertension, has been redetermined at low temperature. The zwitterionic form of the mol-ecule is confirmed, although GAUSSIAN03 calculations suggest that this form is less stable in the gas phase. The unit-cell contraction between 298 and 100 K is approximately isotropic and the largest structual change is in a C-N-C-C torsion angle, which differs by 11.4 (3)° between the room-temperature and low-temperature structures. There are two mol-ecules in the asymmetric unit, both of which contain an intra-molecular N-H⋯N hydrogen bond. In the crystal structure, both mol-ecules form inversion dimers linked by pairs of N-H⋯N hydrogen bonds. Further N-H⋯N and N-H⋯O hydrogen bonds lead to a three-dimensional network. The different hydrogen-bond arrangements and packing motifs in the polymorphs of torasemide are discussed in detail.

4-(3-Methyl-anilino)-N-[N-(1-methyl-ethyl)carbamo-yl]pyridinium-3-sulfon-amidate (torasemide) methanol 0.25-solvate 0.25-hydrate.

The title compound, C(16)H(20)N(4)O(3)S·0.25CH(4)O·0.25H(2)O, is a hydrate/methanol solvate of torasemide, a diuretic drug used in the treatment of hypertension. The asymmetric unit contains two torasemide mol-ecules and half-occupied methanol and water mol-ecules. It is isomorphous with the previously reported nonsolvated T-II form of torasemide. The water mol-ecules contribute to the stability of the structure by participating in an extensive system of O-H⋯O hydrogen bonds; N-H⋯N and N-H⋯O hydrogen bonds are also present. Both asymmetric mol-ecules of torasemide form inversion dimers in the crystal.

Crystal structure of nitromethane up to the reaction threshold pressure.

Angle dispersion X-ray diffraction (AXDX) experiments on nitromethane single crystals and powder were performed at room temperature as a function of pressure up to 19.0 and 27.3 GPa, respectively, in a membrane diamond anvil cell (MDAC). The atomic positions were refined at 1.1, 3.2, 7.6, 11.0, and 15.0 GPa using the single-crystal data, while the equation of state (EOS) was extended up to 27.3 GPa, which is close to the nitromethane decomposition threshold pressure at room temperature in static conditions. The crystal structure was found to be orthorhombic, space group P2(1)2(1)2(1), with four molecules per unit cell, up to the highest pressure. In contrast, the molecular geometry undergoes an important change consisting of a gradual blocking of the methyl group libration about the C-N bond axis, starting just above the melting pressure and completed only between 7.6 and 11.0 GPa. Above this pressure, the orientation of the methyl group is quasi-eclipsed with respect to the NO bonds. This conformation allows the buildup of networks of strong intermolecular O...H-C interactions mainly in the bc and ac planes, stabilizing the crystal structure. This structural evolution determines important modifications in the IR and Raman spectra, occurring around 10 GPa. Present measurements of the Raman and IR vibrational spectra as a function of pressure at different temperatures evidence the existence of a kinetic barrier for this internal rearrangement.

3-Methyl-1,4-dioxo-1,4-dihydro-naphthalen-2-yl 4-amino-benzoate.

The crystal structure of the title compound, C(18)H(13)NO(4), the oxidized form of the drug aminaftone used in venous disease therapy, is characterized by the presence of ribbons of hydrogen-bonded mol-ecules parallel to the [111] crystallographic direction and by stacking inter-actions between rings [centroid-centroid distance between quinone rings = 3.684 (3) Šand between amino-benzoate rings = 4.157 (3) Å] along the ribbons.

Diisoprop-yl{2-[2-(2-oxopyrrolidin-1-yl)acetamido]eth-yl}ammonium hydrogen sulfate.

The structure of the title compound, C(14)H(28)N(3)O(2) (+)·HSO(4) (-), a nootropic drug (pramiracetam) investigated for cognition-enhancing properties, is closely similar to that of the previously determined acetonitrile solvate, both structures being characterized by the presence of ribbons of hydrogen-bonded ions. The pyrrolidine ring adopts an envelope conformation.

Alpha2-adrenoreceptors profile modulation. 3.1 (R)-(+)-m-nitrobiphenyline, a new efficient and alpha2C-subtype selective agonist.

To assess the stereochemical requirements for efficient alpha2C-adrenoreceptor activation, the enantiomeric forms of m-nitrobiphenyline [(+/-)-5] were prepared and tested on cells expressing the human alpha2-adrenoreceptor subtypes. The importance of chirality was confirmed, since the enantiomer (R)-(+)-5 was much more efficient than (S)-(-)-5 in producing alpha2C-activation. Surprising reversal of enantioselectivity was observed with respect to structurally similar biphenyline [(+/-)-1] whose (S)-(-)-form proved the preferred alpha2C-configuration.

Hydrolysis of dinuclear ruthenium complexes [{CpRu(PPh3)2}2(micro,eta(1:1)-L)][CF3SO3]2 (L=P4, P4S3): simple access to metal complexes of P2H4 and PH2SH.

The reaction of [CpRu(PPh(3))(2)Cl] (1) with half an equivalent of P(4) or P(4)S(3) in the presence of AgCF(3)SO(3) as chloride scavenger affords the stable dimetal complexes [{CpRu(PPh(3))(2)}(2)(micro,eta(1:1)-P(4))][CF(3)SO(3)](2).3 CH(2)Cl(2) (2) and [{CpRu(PPh(3))(2)}(2)(micro,eta(1:1)-P(apical)-P(basal)-P(4)S(3))][CF(3)SO(3)](2).0.5 C(7)H(8) (3), in which the tetrahedral P(4) and mixed-cage P(4)S(3) molecules are respectively bound to two CpRu(PPh(3))(2) fragments through two phosphorus atoms. The coordinated cage molecules, at variance with the free ligands, readily react with an excess of water in THF under mild conditions. Among the hydrolysis products, the new, remarkably stable complexes [{CpRu(PPh(3))(2)}(2)(micro,eta(1:1)-P(2)H(4))][CF(3)SO(3)](2) (4) and [CpRu(PPh(3))(2)(eta(1)-PH(2)SH)]CF(3)SO(3) (8) were isolated. In the former, diphosphane, P(2)H(4), is coordinated to two CpRu(PPh(3))(2) fragments, and in the latter thiophosphinous acid, H(2)PSH, is coordinated to the metal centre through the phosphorus atom. All compounds were characterised by elemental analyses and IR and NMR spectroscopy. The crystal structures of 2, 3, 4 and 8 were determined by X-ray diffraction.

Synthesis and characterization of Pd and Pt complexes of 1,3-bis(ferrocenylchalcogeno)propanes: crystal structures of FcSe(CH2)3SeFc and [M{FcE(CH2)3E'Fc}2](PF6)2 (M = Pd, Pt; E, E' = Se, Te; Fc = [Fe(eta5-C5H5)(eta5-C5H4)]).

Reaction of a 1,3-bis(ferrocenylchalcogeno)propane, FcE(CH2)3E'Fc (L: E, E' = Se or Te; Fc = [Fe(eta5-C5H5)(eta5-C5H4)]), with a palladium(II) or platinum(II) precursor [M(NCMe)4](PF6)2 (M = Pd or Pt) in acetonitrile at room temperature led in good yield to the bis-chelate complexes [ML2](PF6)2. The structures of FcSe(CH2)3SeFc and all six complexes have been determined by X-ray crystallography. Electrochemical studies showed that electronic communication between ferrocenyl groups, absent in all three bis(ferrocenylchalcogeno)propanes, is established on complexation only for E = Se and E' = Se or Te, when the through-bond Fe...Fe distance is reduced to 13.17 A or less.

Stabilization of the tautomers HP(OH)2 and P(OH)3 of hypophosphorous and phosphorous acids as ligands.

Treatment of [CpRu(PPh(3))(2)Cl] 1 with the stoichiometric amount of H(3)PO(2) or H(3)PO(3) in the presence of chloride scavengers (AgCF(3)SO(3) or TlPF(6)) yields compounds of formula [CpRu(PPh(3))(2)(HP(OH)(2))]Y (Y = CF(3)SO(3) 2a or PF(6) 2b) and [CpRu(PPh(3))(2)(P(OH)(3))]Y (Y = CF(3)SO(3) 3aor PF(6) 3b) which contain, respectively, the HP(OH)(2) and P(OH)(3) tautomers of hypophosphorous and phosphorous acids bound to ruthenium through the phosphorus atom. The triflate derivatives 2a and 3a react further with hypophosphorous or phosphorous acids to yield, respectively, the complexes [CpRu(PPh(3))(HP(OH)(2))(2)]CF(3)SO(3) 4 and [CpRu(PPh(3))(P(OH)(3))(2)]CF(3)SO(3) 5 which are formed by substitution of one molecule of the acid for a coordinated triphenylphosphine molecule. The compounds 2 and 3 are quite stable in the solid state and in solutions of common organic solvents, but the hexafluorophosphate derivatives undergo easy transformations in CH(2)Cl(2): the hypophosphorous acid complex 2b yields the compound [CpRu(PPh(3))(2)(HP(OH)(2))]PF(2)O(2) 6, whose difluorophosphate anion originates from hydrolysis of PF(6)(-); the phosphorous acid complex 3b yields the compound [CpRu(PPh(3))(2)(PF(OH)(2))]PF(2)O(2) 7, which is produced by hydrolysis of hexafluorophosphate and substitution of a fluorine for an OH group of the coordinated acid molecule. All the compounds have been characterized by elemental analyses and NMR measurements. The crystal structures of 2a, 3a and 7 have been determined by X-ray diffraction methods.

Tetramethylcyclopentadienylselenium derivatives.

Bis(1,2,3,4-tetramethylcyclopentadienyl)selane (1) has been prepared by the reaction of tetramethylcyclopentadienyllithium (Cp(t)Li) with selenium bis(diethyldithiocarbamate). Treatment of Cp(t)Li with elemental selenium, followed by air oxidation, led to loss of the allylic hydrogen atom, and formation of the novel tricyclic compound 1,4,5,6,7,10,11,12-octamethyltricyclo[7.3.0.0]-2,8-diselenadodeca-3,5,9,11-tetraene (2). The sulfur analogue of 2 has been obtained by a similar procedure. The X-ray crystal structures of compounds 1 and 2 have been determined, and the molecular geometry observed for has been probed using DFT calculations.

Easy hydrolysis of white phosphorus coordinated to ruthenium.

The P4 molecule bound to ruthenium as an eta1-ligand in [CpRu(PPh3)2(eta1-P4)]Y (Y = PF6, CF3SO3) undergoes an easy reaction with water in exceedingly mild conditions to yield PH3, which remains coordinated to the [CpRu(PPh3)2] fragment, and oxygenated derivatives.