X-Ray, Raman, infrared, and nuclear magnetic resonance studies of the crystal structure of ammonium tetrachloroaluminate, NH4AlCl4

1978 ◽  
Vol 56 (6) ◽  
pp. 764-771 ◽  
Author(s):  
Gaëtan Mairesse ◽  
Pierre Barbier ◽  
Jean-Pierre Wignacourt ◽  
Annick Rubbens ◽  
Francis Wallart
Keyword(s):  
Raman Scattering ◽  
Infrared Spectra ◽  
Direct Methods ◽  
Polycrystalline Sample ◽  
Ammonium Ion ◽  
Hydrogen Atoms ◽  
System A ◽  
Combination Modes ◽  
Tetrahedral Anion ◽  
Nuclear Magnetic

Ammonium tetrachloroaluminate crystallizes in the orthorhombic System a = 11.022(6) Å, b = 7.072(3) Å, c = 9.257(5) Å, Z = 4, space group Pnma. The structure was determined by direct methods from diffractometer data and refined by full-matrix least-squares procedures to final R and Rw values of 0.053 and 0.069 respectively, for 596 reflections with I > 2σ(I). Hydrogen atoms were not observed. Al—Cl bond lengths are similar to those of other alkaline chloroaluminate salts (Li+, Na+, NO+). The salt is isostructural with NH4ClO4.Crystals and polycrystalline samples of this compound have been studied by Raman scattering above 10 K, and infrared spectra of specimens of a polycrystalline sample have been recorded in Nujol and a fluorolube above 80 K. Both methods enabled us to observe the bands corresponding to the ν1(A2), ν3, and ν4(F2) vibration modes of the ammonium ion but the infrared spectra contain no band due to combination modes involving the librations of this ion. Nuclear magnetic second moment remains equal to 4 G2 over the range 298–80 K. These spectroscopic results, compared to those of other ammonium salts, indicate that the ammonium ion seems to be freely rotating.The four characteristic bands of the AlCl4− tetrahedral anion have been studied by Raman scattering in the 298–10 K temperature range.

Infrared spectra of the ammonium ion in crystals. III. The ammonium ion in crystal sites of symmetry S4

1976 ◽  
Vol 54 (6) ◽  
pp. 892-899 ◽  
Author(s):  
Ian A. Oxton ◽  
Osvald Knop ◽  
Michael Falk
Keyword(s):  
Liquid Nitrogen ◽  
Infrared Spectra ◽  
Ammonium Ion ◽  
Site Symmetry ◽  
Ammonium Ions ◽  
Ammonium Perrhenate ◽  
Combination Modes

The infrared spectra of the isotopically isolated NH3D+ ion in polycrystalline ammonium perrhenate, NH4ReO4, and ammonium tetrachlorocuprate(II) dihydrate, (NH4)2.CuCl4.2H2O, have been recorded at room and liquid-nitrogen temperatures. In the crystals of both compounds the ammonium ions are located at sites of S4 symmetry. The N—D stretching mode of NH3D+ in NH4ReO4 is a singlet, as expected for this site symmetry. In (NH4)2.CuCl4.2H2O, however, a doublet is observed which reveals the occurrence of two non-equivalent orientations of the ammonium ion. The spectra of the undeuterated compounds contain bands due to combination modes involving the librations of the ammonium ion. This shows that the ions are non-rotating.

Infrared spectra of the ammonium ion in crystals. Part VIII. Spectroscopic criteria of highly-bent hydrogen bonds

1980 ◽  
Vol 58 (9) ◽  
pp. 867-874 ◽  
Author(s):  
Osvald Knop ◽  
Wolfgang J. Westerhaus ◽  
Michael Falk
Keyword(s):  
Low Temperature ◽  
Hydrogen Bonds ◽  
Infrared Spectra ◽  
Room Temperature ◽  
Ammonium Ion ◽  
Temperature Transition ◽  
Increasing Temperature

Available evidence suggests that (1) the stretching frequencies of highly-bent hydrogen bonds decrease with increasing temperature, regardless of whether the bonds are static or dynamic in character, to a single acceptor or to several competing acceptors; and (2) departures from symmetric trifurcation (or bifurcation) toward asymmetric situations lower the stretching frequency. In further support of these criteria isotopic probe ion spectra between 10 K and room temperature have been obtained for taurine and for trigonal (NH4)2MF6 (M = Si, Ge, Sn, Ti). Evidence of a low-temperature transition at 100(10) K in trigonal (NH4)2SnF6 is presented, and existence of the previously reported transition at 38.6 K in trigonal (NH4)2SiF6 is confirmed. Symmetry changes associated with these transitions are discussed.

Mid-infrared spectra predict nuclear magnetic resonance spectra of soil carbon

Geoderma ◽  
2015 ◽  
Vol 247-248 ◽  
pp. 65-72 ◽  
Author(s):  
Mohsen Forouzangohar ◽  
Jeffrey A. Baldock ◽  
Ronald J. Smernik ◽  
Bruce Hawke ◽  
Lauren T. Bennett
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Soil Carbon ◽  
Infrared Spectra ◽  
Mid Infrared ◽  
Nuclear Magnetic Resonance Spectra ◽  
Magnetic Resonance Spectra ◽  
Nuclear Magnetic

Dispersion of plasmon-phonon modes in semiconductors: Raman scattering and infrared spectra

1975 ◽  
Vol 16 (2) ◽  
pp. 221-225 ◽  
Author(s):  
V.I. Zemski ◽  
E.L. Ivchenko ◽  
D.N. Mirlin ◽  
Reshina I.I.
Keyword(s):  
Raman Scattering ◽  
Infrared Spectra ◽  
Phonon Modes

Structure and conformation of the hydrochloride of pseudoisocytidine, an antileukemic C-nucleoside

1980 ◽  
Vol 58 (16) ◽  
pp. 1633-1638 ◽  
Author(s):  
George I. Birnabaum ◽  
Kyoichi A. Watanabe ◽  
Jack J. Fox
Keyword(s):  
Heavy Atom ◽  
Three Dimensional ◽  
Direct Methods ◽  
Dimensional Structure ◽  
Side Chain ◽  
Hydrogen Atoms ◽  
Triclinic Space Group ◽  
X Ray Crystallography ◽  
Cell Dimensions ◽  
Sugar Ring

The three-dimensional structure of pseudoisocytidine hydrochloride was determined by X-ray crystallography. The crystals belong to the triclinic space group P1 and the cell dimensions are a = 6.623(2), b = 8.053(2), c = 6.201(2) Å, α = 108.35(2), β = 101.36(2), γ = 93.54(2) °. Intensity data were measured with a diffractometer and the structure was solved by a combination of heavy-atom and direct methods. Least-squares refinement, which included hydrogen atoms, converged at R = 0.040. The conformation about the glycosyl bond is anti (χCC = 21.6°), the pucker of the furanose ring is C(1′)exo, and the conformation of the —CH2OH side chain is gauche–trans (t). An examination of bond lengths indicates that of the three main resonance forms of the isocytosine cation the fully conjugated one contributes more to the structure than the cross-conjugated one. Bond angles in the sugar ring reflect its rare conformation.

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