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Zhulong Chan - One of the best experts on this subject based on the ideXlab platform.
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exogenous application of hydrogen sulfide donor sodium hydrosulfide enhanced multiple abiotic stress tolerance in bermudagrass cynodon dactylon l pers
Plant Physiology and Biochemistry, 2013Co-Authors: Haitao Shi, Zhulong ChanAbstract:As a Gaseous Molecule, hydrogen sulfide (H2S) has been recently found to be involved in plant responses to multiple abiotic stress. In this study, salt (150 and 300 mM NaCl), osmotic (15% and 30% PEG6000) and cold (4 °C) stress treatments induced accumulation of endogenous H2S level, indicating that H2S might play a role in bermudagrass responses to salt, osmotic and cold stresses. Exogenous application of H2S donor (sodium hydrosulfide, NaHS) conferred improved salt, osmotic and freezing stress tolerances in bermudagrass, which were evidenced by decreased electrolyte leakage and increased survival rate under stress conditions. Additionally, NaHS treatment alleviated the reactive oxygen species (ROS) burst and cell damage induced by abiotic stress, via modulating metabolisms of several antioxidant enzymes [catalase (CAT), peroxidase (POD) and GR (glutathione reductase)] and non-enzymatic glutathione antioxidant pool and redox state. Moreover, exogenous NaHS treatment led to accumulation of osmolytes (proline, sucrose and soluble total sugars) in stressed bermudagrass plants. Taken together, all these data indicated the protective roles of H2S in bermudagrass responses to salt, osmotic and freezing stresses, via activation of the antioxidant response and osmolyte accumulation. These findings might be applicable to grass and crop engineering to improve abiotic stress tolerance.
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exogenous application of hydrogen sulfide donor sodium hydrosulfide enhanced multiple abiotic stress tolerance in bermudagrass cynodon dactylon l pers
Plant Physiology and Biochemistry, 2013Co-Authors: Tiantian Ye, Zhulong ChanAbstract:Abstract As a Gaseous Molecule, hydrogen sulfide (H2S) has been recently found to be involved in plant responses to multiple abiotic stress. In this study, salt (150 and 300 mM NaCl), osmotic (15% and 30% PEG6000) and cold (4 °C) stress treatments induced accumulation of endogenous H2S level, indicating that H2S might play a role in bermudagrass responses to salt, osmotic and cold stresses. Exogenous application of H2S donor (sodium hydrosulfide, NaHS) conferred improved salt, osmotic and freezing stress tolerances in bermudagrass, which were evidenced by decreased electrolyte leakage and increased survival rate under stress conditions. Additionally, NaHS treatment alleviated the reactive oxygen species (ROS) burst and cell damage induced by abiotic stress, via modulating metabolisms of several antioxidant enzymes [catalase (CAT), peroxidase (POD) and GR (glutathione reductase)] and non-enzymatic glutathione antioxidant pool and redox state. Moreover, exogenous NaHS treatment led to accumulation of osmolytes (proline, sucrose and soluble total sugars) in stressed bermudagrass plants. Taken together, all these data indicated the protective roles of H2S in bermudagrass responses to salt, osmotic and freezing stresses, via activation of the antioxidant response and osmolyte accumulation. These findings might be applicable to grass and crop engineering to improve abiotic stress tolerance.
David W. H. Rankin - One of the best experts on this subject based on the ideXlab platform.
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molecular structures of free quinuclidine and its adducts with metal trihydrides mh3 m b al or ga studied by gas phase electron diffraction x ray diffraction and quantum chemical calculations
Dalton Transactions, 2007Co-Authors: Derek A. Wann, Frank Blockhuys, Christian Van Alsenoy, Heather E. Robertson, Hans-joerg Himmel, Christina Y. Tang, Andrew R. Cowley, Anthony J. Downs, David W. H. RankinAbstract:The structure of quinuclidine, HC(CH2CH2)3N, has been re-investigated by quantum chemical calculations and by gas-phase electron diffraction (GED). The GED data, together with published rotational constants, have been analysed using the SARACEN method to determine the most reliable structure (rh1) for the Gaseous Molecule. The structures of two adducts of quinuclidine with group 13 trihydride Molecules, MH3 (M = B, Al), have also been determined by GED and quantum chemical calculations. The effect of the coordination of these hydrides to the quinuclidine nitrogen atom has been investigated, and the structural changes and energetics of adduct formation are discussed. We also present the crystal structure of quinuclidine borane.
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Molecular structures of free quinuclidine and its adducts with metal trihydrides, MH3 (M = B, Al or Ga), studied by gas-phase electron diffraction, X-ray diffraction and quantum chemical calculations
Dalton transactions (Cambridge England : 2003), 2007Co-Authors: Derek A. Wann, Frank Blockhuys, Christian Van Alsenoy, Heather E. Robertson, Hans-joerg Himmel, Christina Y. Tang, Andrew R. Cowley, Anthony J. Downs, David W. H. RankinAbstract:The structure of quinuclidine, HC(CH2CH2)3N, has been re-investigated by quantum chemical calculations and by gas-phase electron diffraction (GED). The GED data, together with published rotational constants, have been analysed using the SARACEN method to determine the most reliable structure (rh1) for the Gaseous Molecule. The structures of two adducts of quinuclidine with group 13 trihydride Molecules, MH3 (M = B, Al), have also been determined by GED and quantum chemical calculations. The effect of the coordination of these hydrides to the quinuclidine nitrogen atom has been investigated, and the structural changes and energetics of adduct formation are discussed. We also present the crystal structure of quinuclidine borane.
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molecular structure of trimethylphosphine gallane me3p gah3 gas phase electron diffraction single crystal x ray diffraction and quantum chemical studies
Dalton Transactions, 2003Co-Authors: Christina Y. Tang, Heather E. Robertson, Anthony J. Downs, David W. H. Rankin, Robert A Coxall, Tim M Greene, Lorna Kettle, Simon Parsons, Andrew TurnerAbstract:The structure of the gallane adduct Me3P·GaH3 in the vapour and crystalline states has been investigated. The gas-phase electron-diffraction (GED) pattern has been analysed using the SARACEN method to determine the most reliable structure of the Gaseous Molecule. Salient structural parameters (rh1 structure) were found to be: r(Ga–H) 159.0(11), r(Ga–P) 244.3(6), r(P–C) 184.0(2), r(C–H) 108.3(7) pm; H–Ga–P 98.4(12) and Ga–P–C 117.7(3)°. The structure of a single crystal at 150 K shows that the adduct retains the same monomeric unit in the crystalline phase, with dimensions generally close to those of the Gaseous Molecule and an eclipsed conformation of the C3PGaH3 skeleton. The results are discussed and analysed in the light of quantum chemical calculations and of the properties of related adducts of Group 13 metal hydrides.
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preparation and properties of gallaborane gabh6 structure of the Gaseous Molecule h2ga μ h 2bh2 as determined by vibrational electron diffraction and ab initio studies and structure of the crystalline solid at 110 k as determined by x ray diffraction
Inorganic Chemistry, 2001Co-Authors: A J Downs, David W. H. Rankin, Colin R. Pulham, Paul T. Brain, Tim M Greene, Simon Parsons, Emma Johnsen, Kirsten Aarset, Carole A Morrison, I M MillsAbstract:Gallaborane (GaBH(6), 1), synthesized by the metathesis of LiBH(4) with [H(2)GaCl](n) at ca. 250 K, has been characterized by chemical analysis and by its IR and (1)H and (11)B NMR spectra. The IR spectrum of the vapor at low pressure implies the presence of only one species, viz. H(2)Ga(mu-H)(2)BH(2), with a diborane-like structure conforming to C(2v) symmetry. The structure of this Molecule has been determined by gas-phase electron diffraction (GED) measurements afforced by the results of ab initio molecular orbital calculations. Hence the principal distances (r(alpha) in A) and angles ( angle(alpha) in deg) are as follows: r(Ga.B), 2.197(3); r(Ga-H(t)), 1.555(6); r(Ga-H(b)), 1.800(6); r(B-H(t)), 1.189(7); r(B-H(b)), 1.286(7); angleH(b)-Ga-H(b), 71.6(4); and angleH(b)-B-H(b), 110.0(5) (t = terminal, b = bridging). Aggregation of the Molecules occurs in the condensed phases. X-ray crystallographic studies of a single crystal at 110 K reveal a polymeric network with helical chains made up of alternating pseudotetrahedral GaH(4) and BH(4) units linked through single hydrogen bridges; the average Ga.B distance is now 2.473(7) A. The compound decomposes in the condensed phases at temperatures exceeding ca. 240 K with the formation of elemental Ga and H(2) and B(2)H(6). The reactions with NH(3), Me(3)N, and Me(3)P are also described.
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monochlorogallane physical properties and structure of the Gaseous Molecule h2ga mu cl 2gah2 as determined by vibrational electron diffraction and ab initio studies
Inorganic Chemistry, 2000Co-Authors: Emma Johnsen, Anthony J. Downs, Paul T. Brain, Timothy M Greene, Philip F Souter, Kirsten Aarset, Elizabeth M Page, David A Rice, Alan N Richardson, David W. H. RankinAbstract:Monochlorogallane, synthesized by the metathesis of gallium(III) chloride with an excess of trimethylsilane at ca. 250 K, has been characterized by chemical analysis, by its IR, Raman, and 1H NMR spectra, and by the products of its reaction with trimethylamine. The vibrational spectra of the vapor species isolated in solid Ar, N2, or CH4 matrixes at ca. 12 K imply the presence of only one species, viz. the dimer with an equilibrium structure conforming to D2h symmetry. The structure of this Molecule has been determined by gas-phase electron diffraction (GED) measurements augmented by the results of ab initio molecular orbital calculations. An equilibrium structure with D2h symmetry has been assumed in the analysis of the electron diffraction pattern. However, as the Molecule has a very low frequency Ga(μ-Cl)2Ga ring-puckering mode, a dynamic model was used to describe it with the aid of a set of pseudoconformers spaced at even intervals (Δδ = 5°, δmax = 20°) around the ring-puckering angle δ and Boltzmann...
Heather E. Robertson - One of the best experts on this subject based on the ideXlab platform.
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molecular structures of free quinuclidine and its adducts with metal trihydrides mh3 m b al or ga studied by gas phase electron diffraction x ray diffraction and quantum chemical calculations
Dalton Transactions, 2007Co-Authors: Derek A. Wann, Frank Blockhuys, Christian Van Alsenoy, Heather E. Robertson, Hans-joerg Himmel, Christina Y. Tang, Andrew R. Cowley, Anthony J. Downs, David W. H. RankinAbstract:The structure of quinuclidine, HC(CH2CH2)3N, has been re-investigated by quantum chemical calculations and by gas-phase electron diffraction (GED). The GED data, together with published rotational constants, have been analysed using the SARACEN method to determine the most reliable structure (rh1) for the Gaseous Molecule. The structures of two adducts of quinuclidine with group 13 trihydride Molecules, MH3 (M = B, Al), have also been determined by GED and quantum chemical calculations. The effect of the coordination of these hydrides to the quinuclidine nitrogen atom has been investigated, and the structural changes and energetics of adduct formation are discussed. We also present the crystal structure of quinuclidine borane.
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Molecular structures of free quinuclidine and its adducts with metal trihydrides, MH3 (M = B, Al or Ga), studied by gas-phase electron diffraction, X-ray diffraction and quantum chemical calculations
Dalton transactions (Cambridge England : 2003), 2007Co-Authors: Derek A. Wann, Frank Blockhuys, Christian Van Alsenoy, Heather E. Robertson, Hans-joerg Himmel, Christina Y. Tang, Andrew R. Cowley, Anthony J. Downs, David W. H. RankinAbstract:The structure of quinuclidine, HC(CH2CH2)3N, has been re-investigated by quantum chemical calculations and by gas-phase electron diffraction (GED). The GED data, together with published rotational constants, have been analysed using the SARACEN method to determine the most reliable structure (rh1) for the Gaseous Molecule. The structures of two adducts of quinuclidine with group 13 trihydride Molecules, MH3 (M = B, Al), have also been determined by GED and quantum chemical calculations. The effect of the coordination of these hydrides to the quinuclidine nitrogen atom has been investigated, and the structural changes and energetics of adduct formation are discussed. We also present the crystal structure of quinuclidine borane.
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molecular structure of trimethylphosphine gallane me3p gah3 gas phase electron diffraction single crystal x ray diffraction and quantum chemical studies
Dalton Transactions, 2003Co-Authors: Christina Y. Tang, Heather E. Robertson, Anthony J. Downs, David W. H. Rankin, Robert A Coxall, Tim M Greene, Lorna Kettle, Simon Parsons, Andrew TurnerAbstract:The structure of the gallane adduct Me3P·GaH3 in the vapour and crystalline states has been investigated. The gas-phase electron-diffraction (GED) pattern has been analysed using the SARACEN method to determine the most reliable structure of the Gaseous Molecule. Salient structural parameters (rh1 structure) were found to be: r(Ga–H) 159.0(11), r(Ga–P) 244.3(6), r(P–C) 184.0(2), r(C–H) 108.3(7) pm; H–Ga–P 98.4(12) and Ga–P–C 117.7(3)°. The structure of a single crystal at 150 K shows that the adduct retains the same monomeric unit in the crystalline phase, with dimensions generally close to those of the Gaseous Molecule and an eclipsed conformation of the C3PGaH3 skeleton. The results are discussed and analysed in the light of quantum chemical calculations and of the properties of related adducts of Group 13 metal hydrides.
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2 galla arachno tetraborane 10 h2gab3h8 synthesis properties and structure of the Gaseous Molecule as determined by electron diffraction
Journal of The Chemical Society-dalton Transactions, 1992Co-Authors: Colin R. Pulham, David W. H. Rankin, Anthony J. Downs, Heather E. RobertsonAbstract:The novel mixed hydride 2-galla-arachno-tetraborane(10), H2GaB3H8, has been synthesised by metathesis between neat monochlorogallane and tetra-n-butylammonium octahydrotriborate, [Bun4N]+[B3H8]–, at temperatures near 243 K. The compound has been characterised by chemical analysis, by its vibrational, 1H and 11B NMR, and mass spectra, and by its reaction with ammonia. Electron-diffraction measurements, carried out on the vapour at ca. 273 K, are wholly consistent with the tetraborane(10)-like structure of the Molecule with gallium replacing boron at the 2 position. The ra structure features the following parameters: r[Ga–B(1,3)] 231.2(0.1), r[B(1,3)–B(4)] 185.2(1.3), r(Ga–Ht) 144.2(1.1), r(Ga–Hb) 176.0(2.8) and r(B–Hb) 126.4(0.7) pm; and 114.4(0.6)° for the dihedral angle between the planes GaB(1)B(3) and B(1)B(3)B(4)(Ht= terminal H atom; Hb= bridging H atom). The NMR spectra of solutions imply non-fluxional behaviour of the Molecule in the temperature range 193–283 K. Gallatetraborane(10) decomposes at ambient temperatures to give either metallic gallium, dihydrogen and tetraborane(10) or a solid with the composition GaB2, dihydrogen and diborane according to whether it is in the condensed or Gaseous phase, respectively.
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gallane synthesis physical and chemical properties and structure of the Gaseous Molecule ga2h6 as determined by electron diffraction
Journal of the American Chemical Society, 1991Co-Authors: Colin R. Pulham, David W. H. Rankin, Anthony J. Downs, Michael J Goode, Heather E. RobertsonAbstract:The elusive binary hydride of gallium, [GaH 3 ] n , has at last been synthesized in rigorously conditioned all-glass apparatus by the reaction between monochlorogallane, [H 2 GaCl] 2 , and lithium tetrahydridogallate, LiGaH 4 , near −30°C. The compound, which decomposes to the elements at ambient temperatures, has been characterized by chemical analysis, by its vibrational and 1 H NMR spectra, and by chemical trapping with trimethylamine
Augustine M K Choi - One of the best experts on this subject based on the ideXlab platform.
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heme oxygenase 1 carbon monoxide from basic science to therapeutic applications
Physical Review, 2006Co-Authors: Stefan W Ryter, Jawed Alam, Augustine M K ChoiAbstract:The heme oxygenases, which consist of constitutive and inducible isozymes (HO-1, HO-2), catalyze the rate-limiting step in the metabolic conversion of heme to the bile pigments (i.e., biliverdin and bilirubin) and thus constitute a major intracellular source of iron and carbon monoxide (CO). In recent years, endogenously produced CO has been shown to possess intriguing signaling properties affecting numerous critical cellular functions including but not limited to inflammation, cellular proliferation, and apoptotic cell death. The era of Gaseous Molecules in biomedical research and human diseases initiated with the discovery that the endothelial cell-derived relaxing factor was identical to the Gaseous Molecule nitric oxide (NO). The discovery that endogenously produced Gaseous Molecules such as NO and now CO can impart potent physiological and biological effector functions truly represented a paradigm shift and unraveled new avenues of intense investigations. This review covers the molecular and biochemical characterization of HOs, with a discussion on the mechanisms of signal transduction and gene regulation that mediate the induction of HO-1 by environmental stress. Furthermore, the current understanding of the functional significance of HO shall be discussed from the perspective of each of the metabolic by-products, with a special emphasis on CO. Finally, this presentation aspires to lay a foundation for potential future clinical applications of these systems.
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heme oxygenase colors of defense against cellular stress
American Journal of Physiology-lung Cellular and Molecular Physiology, 2000Co-Authors: Leo E Otterbein, Augustine M K ChoiAbstract:The discovery of the Gaseous Molecule nitric oxide in 1987 unraveled investigations on its functional role in the pathogenesis of a wide spectrum of biological and pathological processes. At that time, the novel concept that an endogenous production of a Gaseous substance such as nitric oxide can impart such diverse and potent cellular effects proved to be very fruitful in enhancing our understanding of many disease processes including lung disorders. Interestingly, we have known for a longer period of time that there exists another Gaseous Molecule that is also generated endogenously; the heme oxygenase (HO) enzyme system generates the majority if not all of the endogenously produced carbon monoxide. This enzyme system also liberates two other by-products, bilirubin and ferritin, each possessing important biological functions and helping to define the uniqueness of the HO enzyme system. In recent years, interest in HO has emerged in numerous disciplines including the central nervous system, cardiovascula...
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carbon monoxide generated by heme oxygenase 1 suppresses endothelial cell apoptosis
Journal of Experimental Medicine, 2000Co-Authors: Sophie Brouard, Leo E Otterbein, Augustine M K Choi, Josef Anrather, Edda Tobiasch, Fritz H Bach, Miguel P SoaresAbstract:Heme oxygenase 1 (HO-1) inhibits apoptosis by regulating cellular prooxidant iron. We now show that there is an additional mechanism by which HO-1 inhibits apoptosis, namely by generating the Gaseous Molecule carbon monoxide (CO). Overexpression of HO-1, or induction of HO-1 expression by heme, protects endothelial cells (ECs) from apoptosis. When HO-1 enzymatic activity is blocked by tin protoporphyrin (SnPPIX) or the action of CO is inhibited by hemoglobin (Hb), HO-1 no longer prevents EC apoptosis while these reagents do not affect the antiapoptotic action of bcl-2. Exposure of ECs to exogenous CO, under inhibition of HO-1 activity by SnPPIX, substitutes HO-1 in preventing EC apoptosis. The mechanism of action of HO-1/CO is dependent on the activation of the p38 mitogen-activated protein kinase (MAPK) signaling transduction pathway. Expression of HO-1 or exposure of ECs to exogenous CO enhanced p38 MAPK activation by TNF-α. Specific inhibition of p38 MAPK activation by the pyridinyl imidazol SB203580 or through overexpression of a p38 MAPK dominant negative mutant abrogated the antiapoptotic effect of HO-1. Taken together, these data demonstrate that the antiapoptotic effect of HO-1 in ECs is mediated by CO and more specifically via the activation of p38 MAPK by CO.
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carbon monoxide generated by heme oxygenase 1 suppresses endothelial cell apoptosis
Journal of Experimental Medicine, 2000Co-Authors: Sophie Brouard, Leo E Otterbein, Augustine M K Choi, Josef Anrather, Edda Tobiasch, Fritz H Bach, Miguel P SoaresAbstract:Heme oxygenase 1 (HO-1) inhibits apoptosis by regulating cellular prooxidant iron. We now show that there is an additional mechanism by which HO-1 inhibits apoptosis, namely by generating the Gaseous Molecule carbon monoxide (CO). Overexpression of HO-1, or induction of HO-1 expression by heme, protects endothelial cells (ECs) from apoptosis. When HO-1 enzymatic activity is blocked by tin protoporphyrin (SnPPIX) or the action of CO is inhibited by hemoglobin (Hb), HO-1 no longer prevents EC apoptosis while these reagents do not affect the antiapoptotic action of bcl-2. Exposure of ECs to exogenous CO, under inhibition of HO-1 activity by SnPPIX, substitutes HO-1 in preventing EC apoptosis. The mechanism of action of HO-1/CO is dependent on the activation of the p38 mitogen-activated protein kinase (MAPK) signaling transduction pathway. Expression of HO-1 or exposure of ECs to exogenous CO enhanced p38 MAPK activation by TNF-alpha. Specific inhibition of p38 MAPK activation by the pyridinyl imidazol SB203580 or through overexpression of a p38 MAPK dominant negative mutant abrogated the antiapoptotic effect of HO-1. Taken together, these data demonstrate that the antiapoptotic effect of HO-1 in ECs is mediated by CO and more specifically via the activation of p38 MAPK by CO.
Anthony J. Downs - One of the best experts on this subject based on the ideXlab platform.
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molecular structures of free quinuclidine and its adducts with metal trihydrides mh3 m b al or ga studied by gas phase electron diffraction x ray diffraction and quantum chemical calculations
Dalton Transactions, 2007Co-Authors: Derek A. Wann, Frank Blockhuys, Christian Van Alsenoy, Heather E. Robertson, Hans-joerg Himmel, Christina Y. Tang, Andrew R. Cowley, Anthony J. Downs, David W. H. RankinAbstract:The structure of quinuclidine, HC(CH2CH2)3N, has been re-investigated by quantum chemical calculations and by gas-phase electron diffraction (GED). The GED data, together with published rotational constants, have been analysed using the SARACEN method to determine the most reliable structure (rh1) for the Gaseous Molecule. The structures of two adducts of quinuclidine with group 13 trihydride Molecules, MH3 (M = B, Al), have also been determined by GED and quantum chemical calculations. The effect of the coordination of these hydrides to the quinuclidine nitrogen atom has been investigated, and the structural changes and energetics of adduct formation are discussed. We also present the crystal structure of quinuclidine borane.
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Molecular structures of free quinuclidine and its adducts with metal trihydrides, MH3 (M = B, Al or Ga), studied by gas-phase electron diffraction, X-ray diffraction and quantum chemical calculations
Dalton transactions (Cambridge England : 2003), 2007Co-Authors: Derek A. Wann, Frank Blockhuys, Christian Van Alsenoy, Heather E. Robertson, Hans-joerg Himmel, Christina Y. Tang, Andrew R. Cowley, Anthony J. Downs, David W. H. RankinAbstract:The structure of quinuclidine, HC(CH2CH2)3N, has been re-investigated by quantum chemical calculations and by gas-phase electron diffraction (GED). The GED data, together with published rotational constants, have been analysed using the SARACEN method to determine the most reliable structure (rh1) for the Gaseous Molecule. The structures of two adducts of quinuclidine with group 13 trihydride Molecules, MH3 (M = B, Al), have also been determined by GED and quantum chemical calculations. The effect of the coordination of these hydrides to the quinuclidine nitrogen atom has been investigated, and the structural changes and energetics of adduct formation are discussed. We also present the crystal structure of quinuclidine borane.
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molecular structure of trimethylphosphine gallane me3p gah3 gas phase electron diffraction single crystal x ray diffraction and quantum chemical studies
Dalton Transactions, 2003Co-Authors: Christina Y. Tang, Heather E. Robertson, Anthony J. Downs, David W. H. Rankin, Robert A Coxall, Tim M Greene, Lorna Kettle, Simon Parsons, Andrew TurnerAbstract:The structure of the gallane adduct Me3P·GaH3 in the vapour and crystalline states has been investigated. The gas-phase electron-diffraction (GED) pattern has been analysed using the SARACEN method to determine the most reliable structure of the Gaseous Molecule. Salient structural parameters (rh1 structure) were found to be: r(Ga–H) 159.0(11), r(Ga–P) 244.3(6), r(P–C) 184.0(2), r(C–H) 108.3(7) pm; H–Ga–P 98.4(12) and Ga–P–C 117.7(3)°. The structure of a single crystal at 150 K shows that the adduct retains the same monomeric unit in the crystalline phase, with dimensions generally close to those of the Gaseous Molecule and an eclipsed conformation of the C3PGaH3 skeleton. The results are discussed and analysed in the light of quantum chemical calculations and of the properties of related adducts of Group 13 metal hydrides.
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monochlorogallane physical properties and structure of the Gaseous Molecule h2ga mu cl 2gah2 as determined by vibrational electron diffraction and ab initio studies
Inorganic Chemistry, 2000Co-Authors: Emma Johnsen, Anthony J. Downs, Paul T. Brain, Timothy M Greene, Philip F Souter, Kirsten Aarset, Elizabeth M Page, David A Rice, Alan N Richardson, David W. H. RankinAbstract:Monochlorogallane, synthesized by the metathesis of gallium(III) chloride with an excess of trimethylsilane at ca. 250 K, has been characterized by chemical analysis, by its IR, Raman, and 1H NMR spectra, and by the products of its reaction with trimethylamine. The vibrational spectra of the vapor species isolated in solid Ar, N2, or CH4 matrixes at ca. 12 K imply the presence of only one species, viz. the dimer with an equilibrium structure conforming to D2h symmetry. The structure of this Molecule has been determined by gas-phase electron diffraction (GED) measurements augmented by the results of ab initio molecular orbital calculations. An equilibrium structure with D2h symmetry has been assumed in the analysis of the electron diffraction pattern. However, as the Molecule has a very low frequency Ga(μ-Cl)2Ga ring-puckering mode, a dynamic model was used to describe it with the aid of a set of pseudoconformers spaced at even intervals (Δδ = 5°, δmax = 20°) around the ring-puckering angle δ and Boltzmann...
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2 galla arachno tetraborane 10 h2gab3h8 synthesis properties and structure of the Gaseous Molecule as determined by electron diffraction
Journal of The Chemical Society-dalton Transactions, 1992Co-Authors: Colin R. Pulham, David W. H. Rankin, Anthony J. Downs, Heather E. RobertsonAbstract:The novel mixed hydride 2-galla-arachno-tetraborane(10), H2GaB3H8, has been synthesised by metathesis between neat monochlorogallane and tetra-n-butylammonium octahydrotriborate, [Bun4N]+[B3H8]–, at temperatures near 243 K. The compound has been characterised by chemical analysis, by its vibrational, 1H and 11B NMR, and mass spectra, and by its reaction with ammonia. Electron-diffraction measurements, carried out on the vapour at ca. 273 K, are wholly consistent with the tetraborane(10)-like structure of the Molecule with gallium replacing boron at the 2 position. The ra structure features the following parameters: r[Ga–B(1,3)] 231.2(0.1), r[B(1,3)–B(4)] 185.2(1.3), r(Ga–Ht) 144.2(1.1), r(Ga–Hb) 176.0(2.8) and r(B–Hb) 126.4(0.7) pm; and 114.4(0.6)° for the dihedral angle between the planes GaB(1)B(3) and B(1)B(3)B(4)(Ht= terminal H atom; Hb= bridging H atom). The NMR spectra of solutions imply non-fluxional behaviour of the Molecule in the temperature range 193–283 K. Gallatetraborane(10) decomposes at ambient temperatures to give either metallic gallium, dihydrogen and tetraborane(10) or a solid with the composition GaB2, dihydrogen and diborane according to whether it is in the condensed or Gaseous phase, respectively.