Showing papers by "Sean Parkin published in 2007"
TL;DR: A strategy to control framework-catenation in MOFs has been presented and contributions to hydrogen uptake from interpenetration and unsaturated metal centers have been resolved.
Abstract: A strategy to control framework-catenation in MOFs has been presented; contributions to hydrogen uptake from interpenetration and unsaturated metal centers have been resolved.
599 citations
TL;DR: In this article, transport and thermodynamic properties of single-crystal SrIrO3 as a function of temperature T and applied magnetic field H were investigated and it was shown that it is a non-Fermi-liquid metal near a ferromagnetic instability, as characterized by the following properties: small ordered moment but no evidence for long-range order down to 1.7 K.
Abstract: We report transport and thermodynamic properties of single-crystal SrIrO3 as a function of temperature T and applied magnetic field H. We find that SrIrO3 is a non-Fermi-liquid metal near a ferromagnetic instability, as characterized by the following properties: (1) small ordered moment but no evidence for long-range order down to 1.7 K; (2) strongly enhanced magnetic susceptibility that diverges as T or T1/2 at low temperatures, depending on the applied field; (3) heat capacity C(T,H) ~ -Tlog T that is readily amplified by low applied fields; (4) a strikingly large Wilson ratio at T< 4K; and (5) a T3/2-dependence of electrical resistivity over the range 1.7 < T < 120 K. A phase diagram based on the data implies SrIrO3 is a rare example of a stoichiometric oxide compound that exhibits non-Fermi-liquid behavior near a quantum critical point (T = 0 and H = 0.23 T).
92 citations
TL;DR: A structural, thermodynamic, and transport study of the newly synthesized quasi-one-dimensional insulators was performed in this paper, and the results indicated the presence of a geometrical frustration that causes incomplete long-range AFM order in these compounds.
Abstract: We report a structural, thermodynamic, and transport study of the newly synthesized ${\mathrm{Sr}}_{5}{\mathrm{Rh}}_{4}{\mathrm{O}}_{12}$, ${\mathrm{Ca}}_{5}{\mathrm{Ir}}_{3}{\mathrm{O}}_{12}$, and ${\mathrm{Ca}}_{4}\mathrm{Ir}{\mathrm{O}}_{6}$ single crystals. These quasi-one-dimensional insulators consist of a triangular lattice of spin chains running along the $c$ axis, and are commonly characterized by a partial antiferromagnetic (AFM) order, a small entropy removal associated with the phase transitions, and a sizable low-temperature specific heat linearly proportional to temperature. ${\mathrm{Sr}}_{5}{\mathrm{Rh}}_{4}{\mathrm{O}}_{12}$ is antiferromagnetically ordered below $23\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ with strong evidence for an Ising character. Isothermal magnetization of ${\mathrm{Sr}}_{5}{\mathrm{Rh}}_{4}{\mathrm{O}}_{12}$ exhibits two steplike transitions leading to a ferrimagnetic state at $2.4\phantom{\rule{0.3em}{0ex}}\mathrm{T}$ and a ferromagnetic state at $4.8\phantom{\rule{0.3em}{0ex}}\mathrm{T}$, respectively. ${\mathrm{Ca}}_{5}{\mathrm{Ir}}_{3}{\mathrm{O}}_{12}$ and ${\mathrm{Ca}}_{4}\mathrm{Ir}{\mathrm{O}}_{6}$ are also antiferromagnetically ordered below 7.8 and $12\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, respectively, and show an unusually large ratio of the Curie-Weiss temperature to the N\'eel temperature. In particular, ${\mathrm{Ca}}_{5}{\mathrm{Ir}}_{3}{\mathrm{O}}_{12}$, which includes both ${\mathrm{Ir}}^{4+}$ and ${\mathrm{Ir}}^{5+}$ ions, reveals that only $S=1∕2$ spins of the ${\mathrm{Ir}}^{4+}$ ions are involved in the magnetic ordering, whereas $S=1$ spins of the ${\mathrm{Ir}}^{5+}$ ions remain disordered. All results suggest the presence of a geometrical frustration that causes incomplete long-range AFM order in these quasi-one-dimensional compounds.
58 citations
TL;DR: Functionalization of the pro-cata positions of pentacene with groups held perpendicular to the aromatic plane, in this case through a rigid 1,3-dioxole unit, yields pentacenes derivatives that are stable and soluble, and still maintain edge-to-face interactions in the solid state.
46 citations
TL;DR: A series of N-alkylated perfluorooctanesulfonamides and structurally related compounds were synthesized by reaction of the corresponding perfluoroalkanesulfonyl fluoride with a suitable primary or secondary amine to minimize steric crowding around the S-N bond.
44 citations
TL;DR: The identity of the latter has been established by X-ray structural, NMR spectroscopic, and DFT computational studies as mentioned in this paper, and it does not appear that 4 possesses agostic interactions in solution.
36 citations
TL;DR: In this article, the experimental evidence suggests that coordinated DMF ligands are labile and the MII(μ-NC)MV linkages are susceptible to fragmentation, which is not the case in our experiments.
28 citations
TL;DR: In this paper, the synthesis of two poly(phenylene ethynylene)s (PPEs) with alternating dialkylbenzene−perfluorobenzene repeating units was reported.
Abstract: We report the synthesis of two poly(phenylene ethynylene)s (PPEs) with alternating dialkylbenzene−perfluorobenzene repeating units. The combination of low volume fraction of solubilizing side chains and enhanced intermolecular π−π stacking renders these materials insoluble. A soluble polymer analogue was realized by using a 1,2,4,5-tetralkoxy benzene in the place of dialkyl benzenes, and its properties are compared to a nonfluorinated analogue. The effects of fluorination and side-chain identity on supramolecular and thermal behavior were investigated by wide-angle X-ray diffraction, differential scanning calorimetry, and polarized optical microscopy. Single-crystal X-ray diffraction from small-molecule model compounds provided further insight, including indication that PPE's composed of alternating 1,2,4,5-tetralkoxy- and 1,2,4,5-tetrafluorobenzenes can assemble to close face-to-face π-stacks. Initial efforts to prepare these same polymers and small-molecule model compounds by alternate pathways are also...
25 citations
TL;DR: In this paper, the X-ray crystal structure determinations of N-methylamine was carried out by using spectroscopic and physical methods, including X-Ray crystal structure determination of di(N-(N-(ferrocenylmethyl))-Nethylammonium cyanoborohydride.
16 citations
TL;DR: Methylalumoxane (MAO) activation of 1-5 under high-temperature solution polymerization conditions produced active single-site ethylene polymerization catalysts that exhibit considerably higher thermal stability than previously reported for Cp2TiCl2/MAO or Ti catalysts supported by related heteroscorpionate or scorpionate ligation.
Abstract: Titanate(1-) complexes Na[(THF)(kappa1-O-bdbpzp)TiCl4] (1) and Na[(THF)(kappa1-O-bdmpzp)TiCl4] (2) and titanate(2-) complexes [Na(THF)]2[(kappa1-O-bdbpzp)2TiCl4] (4) and [Na(THF)]2[(kappa1-O-bdmpzp)2TiCl4] (5) were obtained in good yield from reaction of Na[bdbpzp] or Na[bdmpzp] (sodium salt of 1,3-bis(3,5-di-tert-butylpyrazol-1yl)propan-2-ol or 1,3-bis(3,5-dimethylpyrazol-1yl)propan-2-ol) with TiCl4 (in the appropriate molar ratio) at 0-25 degrees C. Protonolysis of TiCl4 with 1 equiv of bdmpzpH furnished related zwitterionic titanate(1-) complex 3 that possessed a kappa2-N,O-coordinated pyrazolyl-alkoxide with pendant pyrazolium group. Methylalumoxane (MAO) activation of 1-5 under high-temperature solution polymerization conditions produced active single-site ethylene polymerization catalysts that exhibit considerably higher thermal stability (especially 2/MAO, 3/MAO, and 5/MAO) than previously reported for Cp2TiCl2/MAO or Ti catalysts supported by related heteroscorpionate or scorpionate ligation.
12 citations
TL;DR: The structure of a very stable 1:1 compound (or co-crystal) of the cis and trans isomers of 2,3-tetralindiol, the existence of which has been known for nearly a century, has finally been determined.
Abstract: The phases of 1,2,3,4-tetrahydro-2,3-naphthalenediol (or 2,3-tetralindiol) and of 1,2-cyclohexanediol have been investigated. The structure of a very stable 1:1 compound (or co-crystal) of the cis and trans isomers of 2,3-tetralindiol, the existence of which has been known for nearly a century, has finally been determined. No evidence of any analogous compound between the cis and trans isomers of 1,2-cyclohexanediol has been found. The formation of solid-state compounds of stereoisomers is rare; it probably occurs only if the crystal packing of at least one of the isomers is unfavorable, e.g. if at least one of the melting points is lower than expected. Compound formation is usually unlikely because of the difficulty of simultaneously optimizing the translational spacings for both isomers, but that packing problem is avoided in the cis/trans compound of 2,3-tetralindiol because the two isomers are in very similar environments. In the structures of the individual 2,3-tetralindiol isomers there are clear conflicts between the competing packing requirements of the 1,2-diol moiety and the aromatic ring system; these conflicts are resolved better in the co-crystal than in the structures of the individual isomers.
TL;DR: Thermal data suggest the existence of the co-crystal is a consequence of kinetic rather than thermodynamic factors.
Abstract: A 1:1 co-crystal of rac-trans-1,2-C(6)H(10)(OH)(2) and (C(6)H(5))(3)PO has been found that is unusual because there are no strong interactions between the two kinds of molecules, which are segregated into layers. Furthermore, neither pure rac-1,2-cyclohexanediol (CHD) nor pure triphenylphosphine oxide (TPPO) has any obvious packing problem that would make the formation of inclusion complexes likely. The TPPO layers are very much like those found in two of the four known polymorphs of pure TPPO. The hydrogen-bonded ribbons of CHD are similar to those found in other vic-diol crystals. The co-crystals are triclinic (space group P\overline 1), but the deviations from monoclinic symmetry (space group C2/c) are small. The magnitudes of those deviations depend on the solvent from which the crystal is grown; the deviations are largest for crystals grown from acetone, smallest for crystals grown from toluene, and intermediate for crystals grown from ethanol. The deviations arise from incomplete enantiomeric disorder of the R,R and S,S diols; this disorder is not required by symmetry in either space group, but occupancy factors are nearly 0.50 when the structure is refined as monoclinic. When the structure is refined as triclinic the deviations of the occupancy factors from 0.50 mirror the deviations from monoclinic symmetry because information about the partial R,R/S,S ordering is transmitted from one diol layer to the next through the very pseudosymmetric TPPO layer. Analyses suggest individual CHD layers are at least mostly ordered. The degree of order seems to be established at the time the crystal is grown and is unlikely to change with heating or cooling. Thermal data suggest the existence of the co-crystal is a consequence of kinetic rather than thermodynamic factors.
TL;DR: The magnetic and transport properties of a Ba 3 InRu 2 O 9 single crystal are reported in this paper, which is a semiconductor that exhibits variable-range hopping as the transport mechanism in the temperature range 140-600 K.
TL;DR: The asymmetric unit of the racemic form of the title compound, C(12)H(15)NOS, contains four crystallographically independent molecules and the olefinic bond connecting the 2-thienyl and 1-azabicyclo[ 2.2.2]octan-3-ol moieties has Z geometry.
Abstract: The asymmetric unit of the racemic form of the title compound, C(12)H(15)NOS, contains four crystallographically independent molecules. The olefinic bond connecting the 2-thienyl and 1-azabicyclo[2.2.2]octan-3-ol moieties has Z geometry. Strong hydrogen bonding occurs in a directed co-operative O-H...O-H...O-H...O-H R(4)(4)(8) pattern that influences the conformation of the molecules. Co-operative C-H...pi interactions between thienyl rings are also present. The average dihedral angle between adjacent thienyl rings is 87.09 (4) degrees.
Abstract: The title compounds, C20H17NO3S, (I), and C19H15NO2S, (II), were prepared by the reaction of benzo[b]thiophene-2-carbaldehyde with (3,4,5-trimethoxyphenyl)acetonitrile and (3,4-dimethoxyphenyl)acetonitrile, respectively, in the presence of methanolic potassium hydroxide. In (I), the C=C bond linking the benzo[b]thiophene and the 3,4,5-trimethoxyphenyl units has E geometry, with dihedral angles between the plane of the bridging unit and the planes of the two adjacent ring systems of 5.2 (3) and 13.1 (2) degrees, respectively. However, in (II), the C=C bond has Z geometry, with dihedral angles between the plane of the bridging unit and the planes of the adjacent benzo[b]thiophene and 3,4-dimethoxyphenyl units of 4.84 (17) and 76.09 (7) degrees, respectively. There are no significant intermolecular hydrogen-bonding interactions in the packing of (I) and (II). The packing is essentially stabilized via van der Waals forces.
TL;DR: In this article, X-ray crystal structure determination reveals a stacked conformation between the cyclo-decane ring of the parthenolide moiety and the pendant naphthalene ring.
Abstract: Crystals of the title compound, C26H31NO3, were obtained by the reaction of 1-naphthylmethylamine with parthenolide. X-ray crystal structure determination reveals a stacked conformation between the cyclodecane ring of the parthenolide moiety and the pendant naphthalene ring. The configuration of the new chiral center at C11 (the point of attachment of the naphthylmethylamino side group) in the title compound is R, establishing the stereospecificity of the amination reaction.
TL;DR: A structural and thermodynamic study of the newly synthesized single crystal Sr 5 Rh 4 O 12 is reported in this article, which consists of a triangular lattice of spin chains running along the c-axis.
TL;DR: The title compound, C22H29NO3, was obtained by the reaction of benzyl-amine with parthenolide as mentioned in this paper, and the configuration of the new chiral center at C11 is R, establishing the stereospecificity of the amination reaction.
Abstract: The title compound, C22H29NO3, was obtained by the reaction of benzylamine with parthenolide. X-ray crystal structure determination revealed that the configuration of the new chiral center at C11 is R, establishing the stereospecificity of the amination reaction.
TL;DR: The title compound, C7H6BrClO, is a starting material for the synthesis of hydroxylated metabolites of polychlorinated biphenyls (PCBs) as discussed by the authors.
Abstract: The title compound, C7H6BrClO, is a starting material for the synthesis of hydroxylated metabolites of polychlorinated biphenyls (PCBs). The title compound does not display any unusual bond distances and angles. The methoxy group is rotated slightly out of the plane of the benzene ring.
TL;DR: In this article, the title compound, C14H11NO6, was obtained by the reaction of benzyl 2,6-dihydroxy-benzoate with nitric acid and crystallization of the product from ethyl acetate.
Abstract: Crystals of the title compound, C14H11NO6, were obtained by the reaction of benzyl 2,6-dihydroxybenzoate with nitric acid and crystallization of the product from ethyl acetate. In the molecule, the nitro group is essentially coplanar with the attached benzene ring [O—N—C—C = 176.75 (11)°], indicating conjugation with the π-electron system. The benzyloxy group of the ester group is cis with respect to the 2-hydroxy group. The crystal structure is stabilized by intra- and intermolecular hydrogen bonds. The 2-hydroxy group forms an intramolecular hydrogen bond with the nitro group, and the 6-hydroxy group forms an intramolecular hydrogen bond with the ester carbonyl function. In addition, there is intermolecular hydrogen bonding between the 2-hydroxy group of one molecule and the O atom of the 6-hydroxy group of another molecule.
TL;DR: In this paper, 2a-c/1000 MAO catalyst systems with narrow molecular weight distributions (Mw/Mn ǫ = 2.7-2.8) were shown to exhibit high molecular weight polyethylene with a molecular weight distribution that is close to that found for single site catalysts.
01 Jan 2007
TL;DR: In this article, a pseudo-octahedral 2a-c/MAO catalyst system was proposed to obtain high molecular weight polymers with narrow molecular weight distributions (Mw/Mn = 2.7 −2.8).
Abstract: [(RR 0 -admpzp)2Ti(OPr i )2] complexes (2a‐c), synthesized from reaction of Ti(OPr i )3Cl (0.5 equiv) with 1-dialkylamino-3-(3,5dimethyl-pyrazol-1-yl)-propan-2-ol compounds in the presence of triethylamine (0.5 equiv), are pseudo-octahedral with each RR 0 admpzp ligand j 2 -O,N(pyrazolyl) coordinated to the titanium center. In solution, 2a‐c adopt isomeric structures that are in dynamic equilibrium. At 23 ! C, 2a‐c/1000 MAO catalyst systems furnished high molecular weight polymers with narrow molecular weight distributions (Mw/Mn = 2.7‐2.8). At 100 ! C, 2a‐c/MAO catalyst systems exhibited increased polymerization activity and 2c/1000 MAO system furnished high molecular weight polyethylene with a molecular weight distribution (Mw/Mn = 2.1) that is close to that found for single-site catalysts. " 2007 Elsevier B.V. All rights reserved.
TL;DR: In this article, the title compound, C8H7NO6, was obtained by the reaction of methyl 2,6-dihydroxybenzoate with nitric acid and crystallization of the product from ethyl acetate.
Abstract: Crystals of the title compound, C8H7NO6, were obtained by the reaction of methyl 2,6-dihydroxybenzoate with nitric acid and crystallization of the product from ethyl acetate. In the molecule, the nitro group is essentially coplanar with the attached benzene ring [O—N—C—C = 5.2 (3)°] indicating conjugation with the π-electron system. The methoxy group of the ester group is cis with respect to the ortho-nitrohydroxyl group. The crystal structure is stabilized by intra- and intermolecular hydrogen bonds. The ortho-nitrohydroxy group forms an intramolecular hydrogen bond with the nitro group and the para-nitrohydroxy group forms an intramolecular hydrogen bond with the ester carbonyl function. In addition, there is intermolecular hydrogen bonding between the ortho-nitrohydroxyl of one molecule and the O atom of para-nitrohydroxyl of another molecule.
TL;DR: In the title compound, C(9)H(12)N(5)O(3)(+) x Cl(-), the cation is almost entirely planar and the imine double bond is exclusively in the E geometry.
Abstract: In the title compound, C(9)H(12)N(5)O(3)(+) x Cl(-), the cation is almost entirely planar. The imine double bond is exclusively in the E geometry.
TL;DR: The title compound, C18H19NO, was obtained by the reaction of naphthalene-1-carboxaldehyde with 1-aza-bicyclo[2.2] octan-3-one in the presence of methano-lic potassium hydroxide and subsequent reduction of the product with sodium borohydride to the secondary alcohol as mentioned in this paper.
Abstract: The title compound, C18H19NO, in racemic form, was obtained by the reaction of naphthalene-1-carboxaldehyde with 1-azabicyclo[2.2.2]octan-3-one in the presence of methanolic potassium hydroxide and subsequent reduction of the product with sodium borohydride to the secondary alcohol. The double bond linking the 1-naphthyl and 1-azabicyclo[2.2.2]octan-3-ol moieties has Z geometry. The C=C—CH=C torsion angle [42.4 (2)°] indicates a deviation of the 1-naphthyl ring from the plane of the double bond connected to the azabicyclic ring. Part of the 1-azabicyclo[2.2.2]octan-3-ol moiety is disordered, with the approximate ratio of occupancies being 63:37.
TL;DR: In this article, the two aromatic rings of the cation are almost perpendicular to each other, and the cations and anions are connected through hydrogen bonds into a one-dimensional network.
Abstract: In the title compound, C14H15N2O2+·C2F3O2−, the two aromatic rings of the cation are almost perpendicular to each other. The cations and anions are connected through hydrogen bonds into a one-dimensional network. There is an intramolecular N—H⋯O hydrogen bond between the secondary amine group and the carboxylic acid group.
TL;DR: In this article, the title compound, C14H15Cl2NO, was prepared by the base-catalyzed reaction of 2,4-dichloro-benzaldehyde with 1-aza-bicyclo[2.2]octan-3-one and subsequent reduction to the corresponding secondary alcohol.
Abstract: The racemic form of the title compound, C14H15Cl2NO, was prepared by the base-catalyzed reaction of 2,4-dichlorobenzaldehyde with 1-azabicyclo[2.2.2]octan-3-one and subsequent reduction to the corresponding secondary alcohol. In the molecule, the olefinic bond connecting the 2,4-dichlorophenyl ring and 1-azabicyclo[2.2.2]octan-3-ol group has Z geometry. The C=C—CH=C torsion angle [45.3 (3)°] indicates deviation of the 2,4-dichlorophenyl ring from the plane of the double bond connected to the azabicyclic ring. The hydroxyl group is disordered over two sites, the ratio of occupancies being approximately 0.67:0.33. The crystal structure contains intermolecular O—H⋯N hydrogen bonds.
TL;DR: In the title compound, C23H21N3O3, the indoles ring is planar and the phenyl ring of the benzyl group makes a dihedral angle with the best plane of the indole ring of 73.77 (4)°.
Abstract: In the title compound, C23H21N3O3, the indole ring is planar and the phenyl ring of the benzyl group makes a dihedral angle with the best plane of the indole ring of 73.77 (4)°. The double bond connecting the azabicyclic and indole moieties has Z geometry.
TL;DR: Hans-joachim-le hmler et al. as discussed by the authors presented a single-crystography study on the effects of stress on workers' health and reported the following results: T = 9 0 KMean! (CÐC) = 0.004 AuR de facto r =0.023wR de r = 0.061Data-to-param eter ratio = 13.6
Abstract: The University of Iowa, Department ofOccupational and Environment al Health, 100Oakdale Campus, 221 IREH, Iowa City, IA52242-5000 , USACorrespondenc e e-mail:hans-joachim-le hmler@uiowa .eduKey indicato rsSingle-cryst al X-ra y studyT = 9 0 KMean ! (CÐC) = 0.004 AuR facto r = 0.023wR facto r = 0.061Data-to-param eter ratio = 13.6For details of h o w thes e key indicators wereautomatica lly derived from the article, seehttp://journa ls.iucr.org/e.Rece ived 20 February 2007Accepte d 21 February 2007# 2007 Internat ional Union of Crysta llographyAll rights reserved
TL;DR: The title compound of the title compound [Sn(C6H2Cl3)4] has an approximate 4-morphological symmetry as discussed by the authors, which is the same as the symmetry of the lattice.
Abstract: The molecule of the title compound, [Sn(C6H2Cl3)4], occupies a general position in the crystal structure, but shows an approximate \overline{4} molecular symmetry.