| | 2 | Author
| Hideta Ishihara, Keizo Horiuchi, ThorstenM. Gesing, Shi-Qi Dou, J.-Christian Buhl, Hiromitsu Terao | Requires cookie* | | | Title
| I NQR and Crystal Structure Studies of [N(CH 3 ) 4 ] 2 CdI 4  | | | | Abstract
| The temperature dependence of 127 1 NQR and DSC as well as the crystal structure at room temperature of the title compound were determined. This compound shows a first-order phase transition of an order-disorder type at 245 K. Eight 127 I(i^i: m = ±5 <-+ ±|) NQR lines of 79. corresponding eight 127 I(^ 2 : m = ±| <-» • ±|) NQR lines were observed at liquid nitrogen temperature. Three 127 I(^i) NQR lines wfth an intensity ratio of 1:1:2 in the order of decreasing frequency were observed just above the transition point and two NQR lines except for the middle-frequency line disappeared around room temperature. This temperature behavior of NQR lines is very similar to that observed in [N(CH 3)4] 2 Hgl4. Another first-order phase transition takes place at 527 K. The structure of the room-temperature phase was redetermined: orthorhombic, Pnma, Z = 4, a = 1342.8(3), b = 975.7(2), c = 1696.5(3) pm. The NQR result of three lines with an intensity ratio of 1:1:2 is in agreement with this structure. The thermal displacement parameters of atoms in both cations and anions are large. | | | |
Reference
| Z. Naturforsch. 55a, 225—229 (2000); received October 13 1999 | | | |
Published
| 2000 | | | |
Keywords
| NQR, DSC, Crystal Structure, Phase Transition | | | |
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| default:Reihe_A/55/ZNA-2000-55a-0225.pdf | | | | Identifier
| ZNA-2000-55a-0225 | | | | Volume
| 55 | |
| 3 | Author
| Hideta Ishihara, Keizo Horiuchi, V. G. Krishnan, Ingrid Svoboda, Hartmut Fuess | Requires cookie* | | | Title
| Isolated versus Condensed Anion Structure VI: X-ray Structure Analysis and 81 Br NQR of Guanidinium Pentabromodicadmate(II), [C(NH 2 ) 3 ]Cd 2 Br 5 , fns-Hydrazinium Pentabromocadmate(II), [H 2 NNH 3 ] 3 CdBr 5 , and fo's-Hydrazinium Tetrabromocadmate(II)-Tetra Hydrate, [H 2 NNH 3 ] 2 CdBr 4 -4H 2 0 | | | | Abstract
| The structure of the condensed bromocadmate anions in [C(NH 2) 3 ]Cd 2 Br 5 (1) and [H 2 NNH 3 ] 3 CdBr 5 (2) were studied at room temperature by X-ray diffraction. (1) crystallizes with double-chains bridged by Br atoms (orthorhombic, Pmmn, Z= 2, a = 1394.0(5), b = 394.5(1), c = 1086.9(5) pm). This chain structure was not described previously. (1) shows three 8 'Br NQR lines at temperatures between 77 and 323 K. Structural phase transitions take place at 283 K and at 535 K. (2) crystallizes with Br bridged zigzag-chains (monoclinic, P2[, Z=2,a = 943.1(1), b = 778.8(2), c = 942.0(2) pm, ß = 102.10(2)°) and shows a first-order phase transition around 304 K with a large thermal hysteresis. Below the transition point five 81 Br NQR lines are observed at temperatures between 122 and 304 K, and above the transition point four 81 Br NQR lines at tem-peratures between 288 and 353 K. Two 81 Br NQR lines are observed in [H 2 NNH 3 ] 2 CdBr 4 -4H 2 0 (3) at temperatures between 77 and around 320 K with positive temperature coefficients. | | | |
Reference
| Z. Naturforsch. 55a, 390—396 (2000); received November 19 1999 | | | |
Published
| 2000 | | | |
Keywords
| NQR, DSC, Crystal Structure, Phase Transition, Bromocadmate | | | |
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| default:Reihe_A/55/ZNA-2000-55a-0390.pdf | | | | Identifier
| ZNA-2000-55a-0390 | | | | Volume
| 55 | |
| 4 | Author
| Hiroyuki Ishida, Setsuo Kashino, Ryuichi Ikeda | Requires cookie* | | | Title
| Crystal Structure of Trimethylammonium Tetrafluoroborate in Three Solid Phases | | | | Abstract
| The crystal structure of (CH 3) 3 NHBF 4 was studied in three solid phases by X-ray diffraction techniques. The structures of the ionic plastic phase (Phase I) stable above 453 K and Phase II between 384 and 453 K are CsCl-type cubic (a = 5.772(4) Ä) and tetragonal (a = 9.815(5) and c = 6.895(5) A), respectively. The room temperature phase (Phase III) forms a monoclinic lattice (space group P2,/m, a = 5.7017(8), b = 8.5724(9), c = 7.444(1) Ä, and ß = 102.76(1)°). BF 4 ~ ions in this phase were shown to be disordered in four orientations. | | | |
Reference
| Z. Naturforsch. 55a, 765—768 (2000); received June 28 2000 | | | |
Published
| 2000 | | | |
Keywords
| Crystal Structure, X-ray Diffraction, Ionic Plastic Phase, Disorder | | | |
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| default:Reihe_A/55/ZNA-2000-55a-0765.pdf | | | | Identifier
| ZNA-2000-55a-0765 | | | | Volume
| 55 | |
| 5 | Author
| Masao Hashimoto, Shinichi Hashimoto, Hiromitsu Terao, Masayuki Kuma, Haruo Niki, Hiroyuki Ino | Requires cookie* | | | Title
| Crystal Structure and Phase Transition of 4-Aminopyridinium Tetrabromoantimonate(III) as Studied by Bromine and Antimony NQR, Proton NMR, and Single Crystal X-Ray Diffraction | | | | Abstract
| The crystal structure of the room temperature phase (RTP) of the title compound was determined at 297 K (monoclinic, space group C2/c, a = 1384.2(2), b = 1377.8(3), c = 755.5(2) pm, ß = 121.58(1)°). A complicated disorder was found for the cation. A phase transition from the low-temperature phase (LTP) to the RTP was found at (224 ±1) K (T c). The 'H NMR spectra showed a sharp motional narrowing at ca. T=T C , indicating the occurrence of a reorientational motion of the cation in the RTP in accord with the disorder. It was found that another reorientational motion is excited in the LTP. Four 81 Br NQR lines (132.71, 115.38, 61.54 and 59.31 MHz at 77 K) and two Sb NQR lines (53.78 and 33.76 MHz at 77 K) were found in the LTP, while a single 81 Br NQR line was observed at T> 276 K (ca. 121.80 MHz at 300 K). Crystal dynamics are discussed on the basis of the temperature dependence of the NQR, *H NMR line width, and 'H NMR Tj. | | | |
Reference
| Z. Naturforsch. 55a, 167—172 (2000); received August 24 1999 | | | |
Published
| 2000 | | | |
Keywords
| 4-NH 2 PyHSbBr 4, Crystal Structure, Phase Transition, NQR, 'H NMR | | | |
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| default:Reihe_A/55/ZNA-2000-55a-0167.pdf | | | | Identifier
| ZNA-2000-55a-0167 | | | | Volume
| 55 | |
| 7 | Author
| Hiromitsu Terao, Masao Hashimoto, Shinichi Hashimoto, Yoshihiro Furukawa | Requires cookie* | | | Title
| Studies of Structure and Phase Transition in [C(NH 2 ) 3 ]HgBr 3 and [C(NH 2 ) 3 ]HgI 3 by Means of Halogen NQR, NMR, and Single Crystal X-Ray Diffraction | | | | Abstract
| The crystal structure of [C(NH 2) 3 ]HgBr 3 was determined at room temperature: monoclinic, space group C2/c, Z = 4, a = 775.0(2), b = 1564.6(2), c = 772.7(2) pm, ß = 109.12(2)°. In the crystal, almost planar HgBr 3 ~ ions are connected via Hg -Br bonds, resulting in single chains of trigonal bipyramidal HgBr 5 units which run along the c direction. [C(NH 2) 3 ]HgI 3 was found to be isomorphous with the bromide at room temperature. The temperature dependence of the halogen NQR frequencies (77 < 77K < ca. 380) and the DTA measurements evidenced no phase transition for the bromide, but a second-order phase transition at (251 ± 1) K (7 tl) and a first-order one at (210 ± 1) K (T C2) for the iodide. The transitions at T C2 are accompanied with strong supercooling and significant superheating. The room temperature phase (RTP) and the intermediate temperature phase (ITP) of the iodide are characterized by two I(m =i/2~3/2) NQR lines which are assigned to the terminal and the bridging I atoms, respectively. There exist three lines in the lowest temperature phase (LTP), indicating that the resonance line of the bridging atom splits into two. The signal intensities of the 127 I (m =i/2—3/2) NQR lines in the LTP decrease with decreasing temperature resulting in no detection below ca. 100 K. The 127 I(m =i/ 2 ~3/2) NQR frequency vs. temperature curves are continuous at T CL , but they are unusual in the LTP. The T X vs. Tcurves of 'H NMR for the bromide and iodide are explainable by the reorientational motions of the cations about their pseudo three-fold axes. The estimated activation energies of the motions are 35.0 kJ/mol for the bromide, and 24.1, 30.1, and 23.0 kJ/mol for the RTP, FTP, and LTP of the iodide, respectively. | | | |
Reference
| Z. Naturforsch. 55a, 230—236 (2000); received August 23 1999 | | | |
Published
| 2000 | | | |
Keywords
| [C(NH 2 ) 3 ]HgX 3, Crystal Structure, Phase Transition, NQR, 'H NMR | | | |
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| default:Reihe_A/55/ZNA-2000-55a-0230.pdf | | | | Identifier
| ZNA-2000-55a-0230 | | | | Volume
| 55 | |
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