@article {1506, title = {Formation and stability of cubic ice in water droplets}, journal = {Physical Chemistry Chemical Physics}, volume = {8}, number = {1}, year = {2006}, note = {ISI Document Delivery No.: 993PVTimes Cited: 26Cited Reference Count: 28}, pages = {186-192}, type = {Article}, abstract = {There is growing evidence that a metastable phase of ice, cubic ice, plays an important role in the Earth{\textquoteright}s troposphere and stratosphere. Cubic ice may also be important in diverse fields such as cryobiology and planetary sciences. Using X-ray diffraction, we studied the formation of cubic ice in pure water droplets suspended in an oil matrix as a function of droplet size. The results show that droplets of volume median diameter 5.6 mm froze dominantly to cubic ice with stacking faults. These results support previous suggestions that cubic ice is the crystalline phase that nucleates when pure water droplets freeze homogeneously at similar to 235 K. It is also shown that as the size of the water droplets increased from 5.6 to 17.0 mu m, the formation of the stable phase of ice, hexagonal ice, was favoured. This size dependence can be rationalised with heat transfer calculations. We also investigated the stability of cubic ice that forms in water droplets suspended in an oil matrix. We observe cubic ice up to 243 K, much higher in temperature than observed in many previous studies. This result adds to the existing literature that shows bulk ice I-c can persist up to similar to 240 K. The transformation of cubic ice to hexagonal ice also showed a complex time and temperature dependence, proceeding rapidly at. rst and then slowing down and coming to a halt. These combined results help explain why cubic ice forms in some experiments described in the literature and not others.}, keywords = {CRYSTALS, LIQUID WATER, NEUTRON-DIFFRACTION, NUCLEATION, X-RAY-DIFFRACTION}, isbn = {1463-9076}, url = {://000233968300021}, author = {Murray, B. J. and Bertram, A. K.} } @article {5109, title = {Mixing schemes for aqueous dimethyl sulfoxide: Support by X-ray diffraction data}, journal = {Journal of Solution Chemistry}, volume = {30}, number = {10}, year = {2001}, note = {ISI Document Delivery No.: 505UTTimes Cited: 19Cited Reference Count: 18}, month = {Oct}, pages = {885-893}, type = {Article}, abstract = {Aqueous dimethyl sulfoxide (DMSO) was studied by X-ray diffraction at room temperature. The results indicated that there are three distinct composition regions. In the DMSO-rich region, DMSO molecules retain the same molecular arrangement as in the pure, state, while H2O does not show any structural feature. These findings are in the complete agreement with the suggestion by our earlier thermodynamic study on aqueous DMSO.((1)) In the H2O-rich region, there is an indication that DMSO molecules exist as small clusters bound mainly by S=O dipole attraction. Hence, hydrophobic CH3 groups point outward from such a cluster and DMSO acts in effect as a hydrophobic solute. This is also consistent with the findings of our earlier thermodynamic study. In the intermediate region, a gradual change in the radial distribution function with composition was observed.}, keywords = {aqueous DMSO, DIMETHYLSULFOXIDE, intensity, LIQUID, MIXING SCHEMES, NEUTRON-DIFFRACTION, PARTIAL MOLAR ENTHALPIES, WATER MIXTURES, x-ray diffraction}, isbn = {0095-9782}, url = {://000172934500003}, author = {Koga,Yoshikata and Kasahara, Y. and Yoshino, K. and Nishikawa, K.} } @article {4810, title = {Synthesis and bonding in the diamagnetic dinuclear tantalum(IV) hydride species ([P2N2]Ta)(2)(mu-H)(4) and the paramagnetic cationic dinuclear hydride species {([P2N2]Ta)(2)(mu-H)(4)}I-+(-) ([P2N2] = PhP(CH2SiMe2NSiMe2CH2)(2)PPh): The reducing ability of}, journal = {Organometallics}, volume = {19}, number = {19}, year = {2000}, note = {ISI Document Delivery No.: 355PGTimes Cited: 20Cited Reference Count: 48}, month = {Sep}, pages = {3931-3941}, type = {Article}, abstract = {The controlled reaction of the Ta(V) trimethyl species [P2N2]TaMe3, where [P2N2] = PhP(CH2SiMe2NSiMe2CH2)(2)PPh, under 0.5 atm of hydrogen gas produces a partially hydrogenated Ta(V) species, [P2N2]TaMe2(H), of unknown structure. Under 4 atm of hydrogen gas, further hydrogenation does not produce the complex [P2N2]TaH3; instead, reduction of the tantalum center occurs to yield the dinuclear Ta(IV) hydride ([P2N2]Ta)(2)-(mu-H)(4). This diamagnetic tetrahydride fails to react with many reagents, including ethylene and carbon monoxide; however, upon addition of iodomethane, {([P2N2]Ta)(2)(mu-H)(4)}I-+(-) is produced as a paramagnetic green crystalline solid. The number of hydrides in this reaction product was confirmed by a deuterium labeling study. The results of a variable-temperature magnetic susceptibility study of this tetrahydride cation can be partially modeled with the Curie-Weiss law and a large correction for temperature-independent magnetism. Ab initio calculations using density functional theory were performed in an attempt to further understand the influence of the macrocyclic ligand in the bonding in these complexes.}, keywords = {bridging ligands, COMPLEXES, COORDINATION, CRYSTAL, DENSITY-FUNCTIONAL THEORY, DIHYDROGEN, DINITROGEN, MOLECULAR-STRUCTURES, NEUTRON-DIFFRACTION, TA-TA BOND}, isbn = {0276-7333}, url = {://000089393600025}, author = {Fryzuk,Michael D. and Johnson, S. A. and Rettig, S. J.} } @article {4191, title = {Ethylene ligand structures of Os(CO)(4)(C2H4) and Os-2(CO)(8)(C2H4) determined by H-1 NMR in liquid crystal solvents}, journal = {Inorganic Chemistry}, volume = {37}, number = {8}, year = {1998}, note = {ISI Document Delivery No.: ZJ655Times Cited: 2Cited Reference Count: 69}, month = {Apr}, pages = {1720-1728}, type = {Article}, abstract = {The ethylene complexes Os-2(CO)(8)(mu-eta(1),eta(1)-C2H4) (1) and Os(CO)(4)(eta-C2H4) (2) have been studied by H-1 NMR in liquid crystal (nematic phase) solvents. For 1 or 2, three dipolar couplings were observed and assigned to intramolecular geminal, cis, and trans H-1-H-1 dipolar couplings. The H-1 NMR spectrum of Os(CO)(4)((CH2CH2)-C-13)(2-C-13) has also been analyzed and two additional C-13-H-1 dipolar couplinps have allowed determination of the absolute bond angles and relative bond lengths of the ethylene portion of 2 C-13. The observed dipolar couplings for 2-C-13 have been corrected for harmonic vibrations. A comparison of the ethylene geometry of 2 with that of other transition metal ethylene complexes and with free ethylene shows that the (C-2-H-4)Os unit of 2 is best described as a metallacyclopropane. Deuterium substitution is used to demonstrate liquid crystal NMR as a stereochemical probe. The H-1 NMR spectrum of Os-2(CO)(8)(mu-eta(1),eta(1)-(CH2CH2)-C-13) (1-C-13) has also been analyzed in a nematic phase solvent. The dimetallacyclobutane ring of 1-C-13 is best described as two rapidly interconverting ring-puckered conformers of C-2-symmetry. The liquid crystal NMR derived structural parameters for 1-C-13 are compared with those previously determined by neutron diffraction. The solution and solid-state structures are very similar. The ethylene complexes 1 and 2 are proposed as structural and spectroscopic models for ethylene chemisorbed on metal surfaces.}, keywords = {ANISOTROPIC LIQUIDS, CHEMISORBED ETHYLENE, INTERNAL MOTION, METAL-SURFACES, NEMATIC PHASES, NEUTRON-DIFFRACTION, NUCLEAR MAGNETIC-RESONANCE, ORIENTED MOLECULES, SPIN DIPOLAR COUPLINGS, VIBRATIONAL MODEL}, isbn = {0020-1669}, url = {://000073238400007}, author = {Bender, B. R. and Hembre, R. T. and Norton, J. R. and Burnell, E. E.} } @article {3689, title = {Acyclic sulfur-nitrogen compounds. Syntheses and crystal and molecular structures of bis((trifluoromethyl)sulfonyl)amine ((CF3SO2)(2)NH), magnesium hexaaquo bis((trifluoromethyl)sulfonyl)amide dihydrate ([Mg(H2O)(6)][(CF3SO2)(2)N](2)center dot 2H(2)O), an}, journal = {Inorganic Chemistry}, volume = {35}, number = {7}, year = {1996}, note = {ISI Document Delivery No.: UC848Times Cited: 58Cited Reference Count: 69}, month = {Mar}, pages = {1918-1925}, type = {Article}, abstract = {{The syntheses of three acyclic (fluorosulfonyl)- or ((trifluoromethyl)sulfonyl)-nitrogen derivatives and their crystal and molecular structures are reported. The structures of bis((trifluoromethyl)sulfonyl)amine (1; (CF3SO2)(2)NH) and the corresponding anion in magnesium hexaaquo bis((trifluoromethyl)sulfonyl)amide dihydrate (2; [Mg(H2O)(6)][(CF3SO2)(2)N](2) . 2H(2O)) shed some light on the observed high gas-phase acidity of (CF3SO2)(2)NH. Extensive electron delocalization in the anion [(CF3SO)(2)N](-) from planar, sp(2)-hybridized nitrogen into 3d orbitals of sulfur results in a noticeable shortening of the S-N bond on deprotonation. Similar electron delocalization is observed for the third compound, bis(bis(fluorosulfonyl)amino)sulfur (3; (FSO2)(2)NSN(SO2F)(2)), which features planar nitrogens with nearly six equidistant S-N bonds and extremely short S-O and S-F bonds. Compounds 2 and 3 have not been reported previously. Their unexpected, accidental formation and their characterization will be discussed. Compound 1 crystallizes in the space group Peen (No. 56) with a = 16.404(3) Angstrom}, keywords = {ACIDITY, cation, HEXAHYDRATE, NEUTRON-DIFFRACTION, SALTS, SULFONIMIDES}, isbn = {0020-1669}, url = {://A1996UC84800027}, author = {Haas, A. and Klare, C. and Betz, P. and Bruckmann, J. and Kruger, C. and Tsay, Y. H. and Aubke, F.} } @article {3848, title = {Intermolecular interactions in 2-butoxyethanol-DMSO-H2O}, journal = {Journal of Physical Chemistry}, volume = {100}, number = {1}, year = {1996}, note = {ISI Document Delivery No.: TN839Times Cited: 15Cited Reference Count: 23}, month = {Jan}, pages = {433-438}, type = {Article}, abstract = {Excess partial molar enthalpy, H-B(E), and chemical potential, mu(B)(E), of 2-butoxyethanol (B) were determined in ternary mixtures of B, dimethyl sulfoxide (D), and H2O. The data were obtained in small enough mole fraction increments to evaluate the so-called interaction functions, partial derivative H-B(E)/partial derivative x(B), partial derivative H-B(E)/partial derivative x(D), partial derivative mu(B)(E)/partial derivative x(B), and partial derivative mu(B)E/partial derivative x(D). These interaction functions previously proved useful in elucidating the {\textquoteright}{\textquoteright}mixing schemes{\textquoteright}{\textquoteright} in binary aqueous solutions of B and D. For the binary mixtures, it was found that both B and D influenced H2O in the following manner: in the water-rich composition range (region I) within a certain threshold (x(B) < 0.0175 and x(D) < 0.28 at 25 degrees C), both solutes enhance the hydrogen-bonded network of water in their vicinity, and the mixtures retain the percolated nature of the network. At higher B or D concentrations (region II) a qualitatively different mixing scheme becomes operative. The results from this work suggest that, in the ternary mixtures, solute B and D influences the percolated hydrogen bond network of water competitively or cooperatively. The observed effects are in accordance with those characteristic of mixing scheme I in the binary mixtures, as long as the concentration of both solutes is within the threshold values. When either one of the solutes is concentrated beyond its threshold, mixing scheme II seems to set in. It was found that D diminished the positive (unfavorable) enthalpy of B-B interactions and that this effect was almost completely compensated by changes in interaction entropy. Hence, D had little net effect on the Gibbs energy of mutual B interactions, or in other words, D did not weaken the hydrophobic attraction between B molecules. Evaluation of {\textquoteright}{\textquoteright}heterogeneous{\textquoteright}{\textquoteright} B-D interactions in region I suggested that they were weaker than B-B interactions and governed by reorganization of water-water hydrogen bonding rather than interactions between specific groups in B and D. Some implications of these findings on cosolvent effects in aqueous solutions of biopolymers are discussed.}, keywords = {AQUEOUS 2-BUTOXYETHANOL, denaturation, DIMETHYL-SULFOXIDE, LYSOZYME, MIXING SCHEME, MIXTURES, NEUTRON-DIFFRACTION, PARTIAL MOLAR ENTHALPIES, VOLUMES, WATER-RICH REGION}, isbn = {0022-3654}, url = {://A1996TN83900065}, author = {Westh, P. and Koga,Yoshikata} }