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Anhydrous Compound (anhydrous + compound)

Distribution by Scientific Domains
Chemistry83%

Selected Abstracts

Thermal Decomposition Reactions as a Tool for the Synthesis of New Thermodynamic Metastable Modifications: Synthesis, Structures, and Properties of (Formato)nickel(II) Coordination Polymers Based on 4,4,-Bipyridine

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 12 2010
Jan Boeckmann
Abstract The reaction of nickel formate with 4,4,-bipyridine (bipy) in aqueous solution at room temperature leads to the formation of the hydrated compound [Ni(HCO2)2(H2O)(bipy)·4H2O]n (1) reported recently. On heating, compound 1 decomposes into the new anhydrous compound of composition [Ni(HCO2)2(bipy)]n (2II), which decomposes on further heating. Interestingly, if the anhydrous compound is prepared from solution, a new modification 2I is obtained. Investigations on the stability of both forms show that modification 2I presents the thermodynamically most stable form between room and decomposition temperature, whereas modification 2II, which can only be prepared by thermal decomposition, is metastable. In the crystal structure of 2I, the Ni2+ cations are coordinated by four ,2 - anti,anti bridging formato anions and two bridging ,2 -bipy ligands in a slightly distorted octahedralgeometry. The formato anions bridge the metal cations in zigzag chains, which are further connected by ,2 - anti,anti formato anions and bipy ligands to give a three-dimensional coordination network. IR spectroscopic investigations on the metastable form 2II also indicate that all formato anions act as bridging ligands. Magnetic measurements of the hydrated and anhydrous compounds reveal different behavior with a ferromagnetic ordering for compound 2I and an antiferromagnetic ordering for compound 1. For form 2II, only Curie,Weiss paramagnetism was found. [source]

Intermolecular dihydrogen- and hydrogen-bonding interactions in diammonium closo -decahydrodecaborate sesquihydrate

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 1 2010
Teshome B. Yisgedu
The asymmetric unit of the title salt, 2NH4+·B10H102,·1.5H2O or (NH4)2B10H10·1.5H2O, (I), contains two B10H102, anions, four NH4+ cations and three water molecules. (I) was converted to the anhydrous compound (NH4)2B10H10, (II), by heating to 343,K and its X-ray powder pattern was obtained. The extended structure of (I) shows two types of hydrogen-bonding interactions (N,H...O and O,H...O) and two types of dihydrogen-bonding interactions (N,H...H,B and O,H...H,B). The N,H...H,B dihydrogen bonding forms a two-dimensional sheet structure, and hydrogen bonding (N,H...O and O,H...O) and O,H...H,B dihydrogen bonding link the respective sheets to form a three-dimensional polymeric network structure. Compound (II) has been shown to form a polymer with the accompanying loss of H2 at a faster rate than (NH4)2B12H12 and we believe that this is due to the stronger dihydrogen-bonding interactions shown in the hydrate (I). [source]

Imidazolium based ionic liquid crystals: structure, photophysical and thermal behaviour of [Cnmim]Br·xH2O (n = 12, 14; x=0, 1)

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 11 2008
A. Getsis
Abstract The long chain imidazolium halides [Cnmim]Br·xH2O (n = 10, 12; x = 0, 1) have been synthesized and their structural and thermal behaviour together with their photophysical properties characterized. X-ray structure analyses of the monohydrates ([C12mim]Br·H2O: triclinic, P1, no. 2, Z = 2, Pearson code aP112, a = 550.0(5) pm, b = 779.4(5) pm, c = 2296.1(5) pm, , = 81.89(5)°, , = 83.76(5)°, , = 78.102(5)°, 3523 unique reflections with Io > 2,(Io), R1 = 0.0263, wR2 = 0.0652, GooF = 1.037, T = 263(2) K; [C14mim]Br,H2O: triclinic, P1, no. 2, Z = 12, Pearson code aP11, a = 549.86(8) pm, 782.09(13) pm, c = 2511.3(4) pm, , = 94.86(2)°, , = 94.39(2)°, , = 101.83(2)°, 2063 unique reflections with Io > 2,(Io), R1 = 0.0429, wR2 = 0.0690, GooF = 0.770, T = 293(2) K) show for both compounds similar bilayered structures. Sheets composed of hydrophilic structure regions constituted by positively charged imidazolium head groups, bromide anions and hydrogen bonded water alternate with hydrophobic areas formed by interdigitated long alkyl chains belonging to imidazolium cations with different orientation. Combined differential scanning calorimetry and polarizing optical microscopy shows that the monohydrates as well as the anhydrous imidazolium salts are thermotropic liquid crystals which adopt smectic mesophases. The mesophase region is larger in case of the monohydrates when compared to the anhydrous compounds indicating that water obviously stabilizes the mesophase. All compounds show an intense whitish photoluminescence with short lived (1,,1,*) and long lived (1,,3,*) transitions. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Thermal Decomposition Reactions as a Tool for the Synthesis of New Thermodynamic Metastable Modifications: Synthesis, Structures, and Properties of (Formato)nickel(II) Coordination Polymers Based on 4,4,-Bipyridine

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 12 2010
Jan Boeckmann
Abstract The reaction of nickel formate with 4,4,-bipyridine (bipy) in aqueous solution at room temperature leads to the formation of the hydrated compound [Ni(HCO2)2(H2O)(bipy)·4H2O]n (1) reported recently. On heating, compound 1 decomposes into the new anhydrous compound of composition [Ni(HCO2)2(bipy)]n (2II), which decomposes on further heating. Interestingly, if the anhydrous compound is prepared from solution, a new modification 2I is obtained. Investigations on the stability of both forms show that modification 2I presents the thermodynamically most stable form between room and decomposition temperature, whereas modification 2II, which can only be prepared by thermal decomposition, is metastable. In the crystal structure of 2I, the Ni2+ cations are coordinated by four ,2 - anti,anti bridging formato anions and two bridging ,2 -bipy ligands in a slightly distorted octahedralgeometry. The formato anions bridge the metal cations in zigzag chains, which are further connected by ,2 - anti,anti formato anions and bipy ligands to give a three-dimensional coordination network. IR spectroscopic investigations on the metastable form 2II also indicate that all formato anions act as bridging ligands. Magnetic measurements of the hydrated and anhydrous compounds reveal different behavior with a ferromagnetic ordering for compound 2I and an antiferromagnetic ordering for compound 1. For form 2II, only Curie,Weiss paramagnetism was found. [source]

Polymeric, Molecular, and Cation/Anion Arrangements in Chloro-, Bromo-, and Iododiruthenium(II,III) Carboxylate Compounds

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 12 2003
M. Carmen Barral
Abstract The synthesis and characterization of the anhydrous compounds [Ru2X(,-O2CR)4] [R = CH2CH2OPh, X = Cl (1a), Br (2a), I (3a); R = CMePh2, X = Br (5a), I (6a)] and of the solvated complexes [Ru2X(,-O2CR)4(H2O)] [R = CH2CH2OPh, X = Cl (1b), I (3b); R = CMePh2, X = Cl (4b), Br (5b), I (6b)] are described. Thermogravimetric analyses have been used to confirm the anhydrous or solvated natures of the complexes. The crystal structures of 1b·2MeOH, 3b·0.5H2O, and 4b have been investigated by X-ray diffraction and none of them shows the usual polymeric arrangement reported for tetracarboxylatodiruthenium(II,III) compounds. The structure of 3b·0.5H2O consists of cationic and anionic units, [Ru2(,-O2CCH2CH2OPh)4(H2O)2][Ru2I2(,-O2CCH2CH2OPh)4], and represents the first reported crystal structure of a tetracarboxylato(iodo)diruthenium(II,III) derivative. The structures 1b·2MeOH and 4b each show the presence of discrete dinuclear molecules. The crystal structure of [Ru2Cl(,-O2CCMePh2)4(H2O)] demonstrates that diruthenium compounds with the same halide and carboxylate ligands may adopt polymeric or discrete molecular dispositions. Magnetic susceptibility measurements of the complexes in the 2,300 K range have been carried out. Complex 2a shows a strong antiferromagnetic coupling, consistent with the existence of linear chains in the solid state. The complexes [Ru2X(,-O2CR)4(H2O)] show weak through-space antiferromagnetic coupling, in accordance with non-polymeric structures. The magnetic behaviour of 1a, 3a, 5a, and 6a suggests a mixture of arrangements. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source]