Correlation of NQR and Chemical Bond Parameters

Weiß, Alarich; Wigand, Silvia

doi:10.1515/zna-1990-3-403

Cited by 17 publications

(7 citation statements)

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“…This was pointed out many times in the discussion of chemical bond <-* NQR frequencies, see e.g. [29]. In Table 16 we have collected bond distances,8'Br NQR frequencies and the volumes of one unit ACdBr3 in the elementary cell of the structure.…”

Section: Discussionmentioning

confidence: 95%

Structure and Bonding of Tribromocadmates, ACdBr₃, A = NH₄, Rb, Cs, CH₃NH₃, (CH₃)₂NH₂, (CH₃)₄N], [H₂NNH₃, and (H₂N)₃C. An X-ray Diffraction and ^79-81Br NQR Study

Krishnan

Dou

Weiß

1991

Zeitschrift Für Naturforschung A

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The 79-81Br NQR spectra of tribromocadmates with the cations K®, NH®, Rb®, Cs®, CH,NH®, (CH3)2NH®, (CH3)4N®, H2NNH®, and C(NH2)f were studied as functions of temperature from 77 K on up to T>300 K. CsCdBr3 shows a singlet 81 Br NQR spectrum over the whole temperature range studied.[CH3NH3]CdBr3, with one 81Br NQR line spectrum at room temperature, experi ences a phase transition at 167 K; below this temperature an 18-line spectrum is observed. In [(CH3)4N]CdBr3 (phase II), at 290 K, a singlet 81Br NQR is present as is in the high temperature phase I (Tu , = 390 K); the low temperature phase III (T" ", = 160 K has a triplet 81Br NQR spec trum. KCdBr3 shows an 81 Br NQR doublet spectrum, as do Three types of anion chains of CdBr3 have been observed: Single octahedral chains, face con nected; double octahedral chains, edge connected; a trigonal-bipyramidal chain, edge connected. The relation between the crystal structure and the Br NQR is discussed. IntroductionMany solids with the composition ABX3 crystallize in their high temperature phase with the structure of the Perovskite, CaTi03, space group 0^-Pm3m, number of formula units in the unit cell Z = l. The atom A is located at the corners of the cubic unit cell (0, 0, 0), B is at the center of the cell and X at the centers of the cube faces 0 ; 0 , 0, The main feature of the crystal structure is the threedimensional network of corner sharing octahedra BX6. Such an arrangement is not a very stable one and therefore the Perovskite type structures often ex-* Permanent address: Physics Department, Osmania Uni versity, Hyderabad-500 007, India. Reprint requests to Prof. Dr. Al. Weiss, Institut für Physika lische Chemie, Technische Hochschule Darmstadt, Petersenstraße 20, W-6100 Darmstadt, FRG. perience phase transitions, whereby the symmetry of the lattice is lowered and the three-dimensional net of octahedra is changing to two-dimensional connec tions, planes of octahedra, or to one-dimensional chains of octahedra. The oxides AB03 have been treated in numerous investigations within the last 40 years, mainly because of their interesting dielectric properties (ferroelectric phases).Also with X = halogen, a good number of solid phases ABX3, belonging to the class of Perovskites, have been described in literature. As for A and B, the group is more restricted than the family of oxide Perovskites because A = A1 and B = B11. On the other hand X may be F, CI, Br, and I, B may be Zn", Cd", Hg, Ge", Sn", Pb1'.In the course of investigations of the structure and bonding of hexahalogeno complexes, we have studied by 79-81 Br nuclear quadrupole resonance, NQR, some 0932-0784 / 91 / 1100-1063 $ 01.30/0. -Please order a reprint rather than making your own copy.

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Section: Discussionmentioning

confidence: 95%

Structure and Bonding of Tribromocadmates, ACdBr₃, A = NH₄, Rb, Cs, CH₃NH₃, (CH₃)₂NH₂, (CH₃)₄N], [H₂NNH₃, and (H₂N)₃C. An X-ray Diffraction and ^79-81Br NQR Study

Krishnan

Dou

Weiß

1991

Zeitschrift Für Naturforschung A

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“…In the isolated TNT molecule the energy barrier for nitro group rotation is calculated to be 10.6 kJ mol -1 [24], indicating that solid state interactions must make a major contribution to our measured values. For C-NO 2 groups in other molecules, where this behaviour is expected to be a common feature [28,29], the literature values for otational activation energies vary considerably. For example they are estimated to be larger than 31 kJ mol -1 in m-chloronitrobenzene [17] [31] have been measured.…”

Section: The 14 N Nqr Relaxation Times and Signal Decay Times Of Tntmentioning

confidence: 99%

14N NQR, relaxation and molecular dynamics of the explosive TNT

Smith

Rowe

Althoefer

et al. 2015

Solid State Nuclear Magnetic Resonance

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Multiple pulse sequences are widely used for signal enhancement in NQR detection applications. Since the various 14 N NQR relaxation times, signal decay times and frequency of each NQR line have a major influence on detection sequence performance, it is important to characterise these parameters and their temperature variation, as fully as possible. In this paper we discuss such measurements for a number of the ν + and ν − NQR lines of monoclinic and orthorhombic TNT and relate the temperature variation results to molecular dynamics. The temperature variation of the 14 N spin-lattice relaxation times T 1 is interpreted as due to hindered rotation of the NO 2 group about the C-NO 2 bond with an activation energy of 89 kJ mol -1 for the ortho and para groups of monoclinic TNT and 70 kJ mol -1 for the para group of orthorhombic TNT.

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“…Thus the theory allows for a correlation of the NQR frequencies with the bond distances [12,13], Hence our main interest is in the correlation of N-Cl bond lengths and the 35 C1 (N) NQR frequencies.…”

Section: C1nqrmentioning

confidence: 99%

The Bond N-Cl. (III): A ³⁵Cl NQR and X-Ray Diffraction Study of N-Chloro-N-(2,6-Dichlorophenyl)-Acetamides

Gowda

Dou

Weiß

1996

Zeitschrift Für Naturforschung A

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The crystal structures at room temperature of the N-chloro-N-(2,6-dichlorophenyl)-chloroacetamides 2,6-Cl 2 C 6 H 3 NClCOCCl 3 (1) and 2,6-Cl 2 C 6 H 3 NClCOCH 2 Cl (2) have been determined.(1): orthorhombic, Pbca. Z = 8, a = 2051.7(8) pm, b= 1134.8(4) pm, c = 1089.0(4) pm. (2): orthorhombic, Pbca, Z = S, a = 2078.7 (4) pm, b= 1487.9(4) pm, c = 694.0 (2) pm. The "CI NQR spectrum of (1) There is no problem in assigning in both compounds, on the basis of the known 35 C1 NQR frequency scale, the line Vj to the CI atom attached to the nitrogen atom and the lines v 5 and v 6 to the ring chlorines (Cl <2) and Cl (6) ). The crystal structures and NQR spectra of (1) and (2) are discussed together with literature data for 2,6-Cl 2 C 6 H 3 NHCOR, C 6 H 5 NC1C0R (where R = CC1 3 , CClH 2 fand other substituted acetamides.

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Correlation of NQR and Chemical Bond Parameters

Cited by 17 publications

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Structure and Bonding of Tribromocadmates, ACdBr₃, A = NH₄, Rb, Cs, CH₃NH₃, (CH₃)₂NH₂, (CH₃)₄N], [H₂NNH₃, and (H₂N)₃C. An X-ray Diffraction and ^79-81Br NQR Study

Structure and Bonding of Tribromocadmates, ACdBr₃, A = NH₄, Rb, Cs, CH₃NH₃, (CH₃)₂NH₂, (CH₃)₄N], [H₂NNH₃, and (H₂N)₃C. An X-ray Diffraction and ^79-81Br NQR Study

14N NQR, relaxation and molecular dynamics of the explosive TNT

The Bond N-Cl. (III): A ³⁵Cl NQR and X-Ray Diffraction Study of N-Chloro-N-(2,6-Dichlorophenyl)-Acetamides

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Correlation of NQR and Chemical Bond Parameters

Cited by 17 publications

References 0 publications

Structure and Bonding of Tribromocadmates, ACdBr3, A = NH4, Rb, Cs, CH3NH3, (CH3)2NH2, (CH3)4N], [H2NNH3, and (H2N)3C. An X-ray Diffraction and 79-81Br NQR Study

Structure and Bonding of Tribromocadmates, ACdBr3, A = NH4, Rb, Cs, CH3NH3, (CH3)2NH2, (CH3)4N], [H2NNH3, and (H2N)3C. An X-ray Diffraction and 79-81Br NQR Study

14N NQR, relaxation and molecular dynamics of the explosive TNT

The Bond N-Cl. (III): A 35Cl NQR and X-Ray Diffraction Study of N-Chloro-N-(2,6-Dichlorophenyl)-Acetamides

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Structure and Bonding of Tribromocadmates, ACdBr₃, A = NH₄, Rb, Cs, CH₃NH₃, (CH₃)₂NH₂, (CH₃)₄N], [H₂NNH₃, and (H₂N)₃C. An X-ray Diffraction and ^79-81Br NQR Study

Structure and Bonding of Tribromocadmates, ACdBr₃, A = NH₄, Rb, Cs, CH₃NH₃, (CH₃)₂NH₂, (CH₃)₄N], [H₂NNH₃, and (H₂N)₃C. An X-ray Diffraction and ^79-81Br NQR Study

The Bond N-Cl. (III): A ³⁵Cl NQR and X-Ray Diffraction Study of N-Chloro-N-(2,6-Dichlorophenyl)-Acetamides