| | 22 | Author
| Masahiko Suhara, Koichi Mano | Requires cookie* | | | Title
| NQR and Phase Transitions in Hexachlorocyclopropane Crystal  | | | | Abstract
| 35 C1 NQR and DSC studies on phase transitions in hexachlorocyclopropane (HCCP), C 3 C1 6 , are reported. It is found that HCCP has three solid phases: A high temperature disordered phase (Phase I) above 301 K (no NQR spectrum was observed); a metastable phase (Phase II), which exhibited 6 NQR lines from 77 to 270 K; a low temperature phase (Phase III) in which a 24-multiplet of 35 C1 NQR lines at 77 K, the most complex multiplet spectrum ever reported was observed. DSC measurement shows a A-type transition at 301 K and a broad transition of very slow rate at 285 K. The structure and mechanism of phase transitions in HCCP crystal are discussed. | | | |
Reference
| Z. Naturforsch. 45a, 339—342 (1990); received August 23 1989 | | | |
Published
| 1990 | | | |
Keywords
| Nuclear quadrupole resonance, Phase transition, Crystal structure, Differential scan-ning calonmetry, Order-disorder transition | | | |
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| default:Reihe_A/45/ZNA-1990-45a-0339.pdf | | | | Identifier
| ZNA-1990-45a-0339 | | | | Volume
| 45 | |
| 23 | Author
| Gary Wulfsberg, Debra Jackson, William Ilsley, Shi-Qi Dou, Alarich Weiss, John Gagliardi | Requires cookie* | | | Title
| Coordination of OrfÄö-Chlorines in Copper (I) and Silver (I) 2,6-Di-and 2,4,6-Trichlorophenolates Crystal Structure of (2,4,6 -Trichlorophenolato-O, CI) bis (triphenylphosphine) silver (I) | | | | Abstract
| The crystal structure of (Ph 3 P) 2 AgOC 6 H 2 Cl 3 (I) is reported along with the syntheses and 35 C1 and 63 Cu NQR spectra of I and several related silver (I) and copper (I) 2,6-di-and 2,4,6-trichlorophe-nolates containing phosphines, phosphites, and pyridine as co-ligands. I crystallizes in space group P2 Jc with a= 16.692(4) Ä, b= 17.942 (4) A, c= 12.857 (3) Ä, /? = 97.60 (1)°, F = 3816.68 Ä 3 , and Z = 4. The final R (F) = 0.0475 and R (W) = 0.0396. Ag is coordinated in a trigonal planar geometry by the P atoms of the two triphenylphosphine ligands and the O atom of the chlorophenolate; Ag is then capped by one ortho-chlorine of the trichlorophenolate ligand at a distance of 3.160 (2) Ä. In the 35 C1 NQR spectrum of this compound the two orf/io-chlorines of the trichlorophenolate ligand have a large frequency difference of 1.500 MHz, indicating that one ortho-chlorine is coordinated to the silver; 35 C1 NQR spectra of related complexes are also presented and discussed. The 35 C1 NQR frequency differences of coordinated and non-coordinated orr/io-chlorines in metal chlorophenolates correlate well with the metal-chlorine distances but not with the metal-chlorine-carbon bond angles. A different correlation is found for the silver complexes of dichloroalkanes; possible reasons for this are discussed. | | | |
Reference
| Z. Naturforsch. 47a, 75—84 (1992); received July 15 1991 | | | |
Published
| 1992 | | | |
Keywords
| Nuclear quadrupole resonance, Chlorophenolates, Crystal structure, Chlorocarbons as ligands, Silver(I) complexes | | | |
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| default:Reihe_A/47/ZNA-1992-47a-0075.pdf | | | | Identifier
| ZNA-1992-47a-0075 | | | | Volume
| 47 | |
| 24 | Author
| Masao Hashimoto, Takahiro Isono, Noriko Yomesaka, Haruo Niki, Hiroshi Kyan, Takeshi Hamagawa | Requires cookie* | | | Title
| Reorientation of the CC1 3 Group in Chloral 4-Chlorobenzyl- hemiacetal. A Pulsed 35 C1 NQR and X-ray Study | | | | Abstract
| The crystal structure of the title compound was determined at 291 K: monoclinic, space group C^h-P21/n, Z = 4, a = 1693.2(1), 6 = 579.3(1), c = 1232.5(1) pm, and ß = 107.21 (1)°, R = 0.0415. A sharp decrease of of Cl NQR found at T> 270 K for the CC13 group is attributed to the reorientation of the group over a potential barrier of ca. 50 kJ/mol. Intermolecular interactions between the CC13 and the neighboring atoms seem to dominate the magnitude of the potential barrier. T{~ 1 of the 35 C1 NQR of the Cl atom on the benzene ring obeyed the T 2 law well in the range 80 < T/K <270, while at T>280 K it deviated from the T 2 law. | | | |
Reference
| Z. Naturforsch. 47a, 293—298 (1992); received July 25 1991 | | | |
Published
| 1992 | | | |
Keywords
| Crystal structure, Hydrogen bond, Chlorine NQR, Spin lattice relaxation, Atom-atom potential method | | | |
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| default:Reihe_A/47/ZNA-1992-47a-0293.pdf | | | | Identifier
| ZNA-1992-47a-0293 | | | | Volume
| 47 | |
| 25 | Author
| Hirom Itsu Terao, TsutomuO., Kichiro Koto, Shi-Qi, AlarichW. Eiss2 | Requires cookie* | | | Title
| 81 Br NQR and Crystal Structure of Ethylammonium Tribromomercurate(II), CHgCHjNI-^HgBrg | | | | Abstract
| The 81Br NQR triplet spectrum of (CH3 CH2 NH)®(HgBr3)e was measured in the range 77 K to near the m.p. (99~106°C). decreases strongly with increasing temperature, exhibiting 136.784 MHz at 77 K and 128.129 MHz at 298 K. v2 decreases from 82.060 MHz at 77 K to 76.322 MHz at 298 K. v3 increases with temperature, showing v3 = 81.292 MHz at 77 K and 84.903 MHz at 298 K. Replacement of the ammonium hydrogens by deuterium produces a negative shift of Vj and positive ones of v2 and v3 at high temperatures. These shifts change with temperature from | — 0| up to |~ 2 0 0 | kHz. The crystal structure of the title compound was determined at room temperature: P 21/m, Z = 2, a = 1021.6(8) pm, b = 643.0(6) pm, c = 691.8(6) pm, ß = 96.96 (4)°. The coordination of the mercury atom by the bromines is trigonal bipyramidal; by formation of bridges Hg • • ■ Br • • ■ Hg by one of the three bromines (Br(2)) of the planar HgBr® ions a double chain of trigonal bipyramids is formed, running along the b-axis of the crystal. B r 1' and Br(3) are single bonded to Hg. The hydrogen bonds N -H • • • Br(1 and N -H • ■ • Br(' (twice), connect the H g-B r chains to planes lying parallel to the be plane at x = 0. The relations between the Br-NQR spectrum and the structure are discussed. | | | |
Reference
| Z. Naturforsch. 49a, 202—208 (1994); received August 16 1993 | | | |
Published
| 1994 | | | |
Keywords
| Mercury(II) Bromide Complex, Crystal Structure, 81Br NQR, * H -2D isotope effect, H-bonding | | | |
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| default:Reihe_A/49/ZNA-1994-49a-0202.pdf | | | | Identifier
| ZNA-1994-49a-0202 | | | | Volume
| 49 | |
| 26 | Author
| Hiromitsu Terao, Tsutomu Okuda, Sachiyo Uyama, Hisao Negita, Shi-Qi Dou, Hartmut Fuess, Alarich Weiss | Requires cookie* | | | Title
| Crystal Structure Refinement and Single Crystal 81 Br Zeeman NQR Study of KHgBr 3 H 2 0 | | | | Abstract
| Three 81 Br NQR resonance lines of KHgBr 3 H 2 0 were detected between 77 K and room temperature. From the Zeeman effect measurement on a single crystal the nuclear quadrupole coupling constants (e 2 qQ/h) and the asymmetry parameters (r/) were obtained, which are 228.42 MHz and 0.005, 226.24 MHz and 0.005, and 108.76 MHz and 0.465 for e'qQIh and rj at 295 K, respectively. Large deviations of the observed directions of electric field gradient tensors from the directions expected from previous X-ray results have been found. With the present X-ray redetermination, 1 Br NQR and structure are in good agreement. The structure and bonding in the compound are discussed. | | | |
Reference
| Z. Naturforsch. 51a, 1197—1202 (1996); received June 14 1996 | | | |
Published
| 1996 | | | |
Keywords
| KHgBr v H 2 0, X-Ray analysis, NQR, Crystal structure, Chemical bonding | | | |
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| default:Reihe_A/51/ZNA-1996-51a-1197.pdf | | | | Identifier
| ZNA-1996-51a-1197 | | | | Volume
| 51 | |
| 27 | Author
| Hiromitsu Terao, Masao Hashimoto\, Tsutomu Okuda, Alarich Weiss | Requires cookie* | | | Title
| Phase Transitions and Crystal Structure of Dimethylammonium Tribromomercurate(II), (CH 3 ) 2 NH 2 HgBr 3 , as Studied by 81 Br NQR and Single Crystal X-ray Diffraction | | | | Abstract
| The temperature dependence of the 81 Br NQR frequencies of the title compound has revealed the presence of three phases (I, II and III, in the order of decreasing temperature): T cl (II -1) = (318 ± 10) K and T c2 (III -II) = (202 ± 1) K. The transitions were confirmed by thermal analysis (DTA). Both of the II-I and I-II transitions exhibited strong hysteresis (/. e., superheating and supercooling, respectively). The crystal data, determined by single crystal X-ray diffraction, are: monoclinic, space group P2/a, a = 1384.8(3), b = 934.7(4), c = 1452.0(2) pm, ß = 104.10(1)°, Z= 8, R = 0.076. The crystal has two crystallographically independent cations (CH 3) 2 NH 2 + and an infinite chain of anions almost in the c-direction. The anion chain is considered to consist of a HgBr 2 molecule and two different HgBr 4 2 ~ anions which are interconnected via weak intermolecular Hg-Br bonds. The splitting patterns of the 8 'Br NQR spectra indicate that rearrangements of the Hg-Br bonds are slight at the III-II transition but serious at the II-I transition. Some of the 81 Br NQR lines show anomalous temperature coefficients, attributable probably to thermal motions of cations. | | | |
Reference
| Z. Naturforsch. 53a, 559—567 (1998); received January 26 1998 | | | |
Published
| 1998 | | | |
Keywords
| (CH 3 ) 2 NH 2 HgBr 3, X-Ray Analysis, NQR, Phase Transition, Crystal Structure | | | |
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| default:Reihe_A/53/ZNA-1998-53a-0559.pdf | | | | Identifier
| ZNA-1998-53a-0559 | | | | Volume
| 53 | |
| 28 | 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 | |
| 29 | Author
| Magdolna Hargittai, Gabor Jancsó | Requires cookie* | | | Title
| Correlation of Crystal Structure and Vapor Composition of Metal Dihalides | | | | Abstract
| The presence of dimers in the vapor of metal dihalides, as seen in electron diffraction experiments, is found to be correlated with the crystal structure of the halide and with the difference in the heat of vaporization between monomers and dimers. If the dimeric molecule cannot be recognized as a unit in the crystal, dimers are not detected in the vapor. If dimeric molecules are discernible in the crystal, they will be observed in the vapor if their heat of vaporization is not greater than that of the monomer by more than 10kcal/mol. | | | |
Reference
| Z. Naturforsch. 48a, 1000—1004 (1993); received July 20 1993 | | | |
Published
| 1993 | | | |
Keywords
| Crystal structure, Vapor composition, Metal dihalides, Correlation of structure and vapor composition, Gas-phase electron diffraction | | | |
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| default:Reihe_A/48/ZNA-1993-48a-1000.pdf | | | | Identifier
| ZNA-1993-48a-1000 | | | | Volume
| 48 | |
| 30 | Author
| A. R. Ofial, S.-Q Dou, V. G. Krishnan, H. Paulus, H. Fuess, Al Weiss | Requires cookie* | | | Title
| X-Ray and 35 C1 NQR Studies on the Trichloroacetyl Group in Covalent and Ionic Compounds of L-Valine and DL-Valine | | | | Abstract
| The crystal structures and 35 C1 NQR of trichloroacetyl-DL-valine (1), trichloroacetyl-L-valine (2), as well as the salts of trichloroacetic acid with DL-valine (3) and L-valine (4) have been investigated. Crystal data are for (1): Monoclinic, C2/c, a= 15.835(4) Ä, b= 10.481 (3) Ä, c = 14.046(4) A, /? = 103.28(1), Z = 8; (2): Orthorhombic, P2 1 2 1 2 1 , a = 12.117(3) Ä, 6=10.896(3) Ä, c= 8.718(2) Ä, Z = 4; (3): Triclinic, PI, a= 17.269(3) Ä, 6 = 8.504(3) Ä, c = 10.427(4) A, a = 105.38(2), £ = 96.98(2), y = 96.24(2), Z = 2; (4): Monoclinic, P2 1? a = 10.378(4) A, 6 = 20.349(8) A, c= 11.890(5) A, B = 95.28(2), Z = 8. The onset of rotational motion within the trichloroacetyl groups bleaches out 35 C1 NQR lines between 115 K and 185 K for (l)-(4). While TCA-L-valine (1), TCA-DL-valine (2), and TCA*) • DL-valine (+) (3) do not show any phase transition in the temperature range 77 K to 295 K, TCA <_) • L-valine (+) (4) shows more than one phase transition above 77 K before the three NQR signals bleach out at 164 K. | | | |
Reference
| Z. Naturforsch. 52a, 249—258 (1997); received August 30 1996 | | | |
Published
| 1997 | | | |
Keywords
| 35 C1 NQR study, trichloroacetyl, valine, crystal and molecular structure | | | |
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| default:Reihe_A/52/ZNA-1997-52a-0249.pdf | | | | Identifier
| ZNA-1997-52a-0249 | | | | Volume
| 52 | |
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