Deuteron Magnetic Resonance (DMR) - Study on CD3NH3HgCl3

Körfer, M.; Kind, R.; Fueß, H.

doi:10.1515/zna-1989-1208

Cited by 7 publications

(8 citation statements)

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“…On the other hand, such excitations may create a decrease of N z through increasing amplitudes of tortional vibrations in the main bonds of the CI atoms [6], Thus, when the increase in the frequency due to the increase of N x (and N y ) overwhelms the decrease in the frequency due to the increase of N z , the observed frequency may increase with increasing temperature. This explanation may be applicable for v" and partly for v 4 in the present case. Their frequencies are low at low temperature; for v" a positive temperature dependence is observed in the observed temperature range, and for v 4 a positive dependence is observed initially, and then the frequency decreases with a small temperature coefficient.…”

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confidence: 51%

“…All crystallographically nonequivalent Br atoms seem to be involved in H-bonds having short N • • • Br distances in the range 3.38 to 3.55 Ä. In addition, it is known that the motions of CH3NH3 ions are quite large in the present type of crystals [4]. Then we may ascribe the unusual behavior of the resonance lines (a widelyranged frequency, a positive temperature dependence, and a large negative temperature dependence) to the H-bonding and the motions of CH3NH3 ions because other special inter-and intramolecular bond schemes and phase transitions do not seem to exist.…”

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confidence: 70%

“…The crystal structure of the 2:1 stoichiometric compounds consisting of the same chemical species, (CH 3 NH 3 ) 4 HgBr 4 and (CH 3 NH 3 ) 4 HgI 4 , has been also determined by Körfer et al [3]. There exist isolated units of HgX 4~ with slight deformation from a regular tetrahedron in both structures which are connected with each other by the H-bonds.…”

Section: Introductionmentioning

confidence: 97%

“…Their frequencies are low at low temperature; for v" a positive temperature dependence is observed in the observed temperature range, and for v 4 a positive dependence is observed initially, and then the frequency decreases with a small temperature coefficient. The Hg-Br bonds of the Br atoms for v" presumably undergo smaller tortional vibrations compared to that of the Br atom for v 4 .…”

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confidence: 99%

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⁸¹Br and ¹²⁷ I NQR Studies of (CH₃NH₃)₂HgBr₄ and (CH₃NH₃)₂HgI₄

Terao

Okuda

Minami

et al. 1992

Zeitschrift Für Naturforschung A

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2 HgBr 4 . Both negative and positive frequency differences between the deuterated and the nondeuterated compound have been observed at 77 K. The relatively large asymmetry parameters in the iodine compound decrease with increasing temperature, indicating the existence of H-bonds. The present results are interpreted qualitatively by considering the effects of H-bonding, N-H • • • X, between the halogen atoms and the CH 3 NH 3 ions which may undergo large molecular motions. It is suggested that not only frequency-lowering but also frequency-rising effects may be produced, depending on the direction of the H-bond, i.e., the angle between the Hg-X bond and the X • • • H bond.

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confidence: 51%

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confidence: 70%

Section: Introductionmentioning

confidence: 97%

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confidence: 99%

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⁸¹Br and ¹²⁷ I NQR Studies of (CH₃NH₃)₂HgBr₄ and (CH₃NH₃)₂HgI₄

Terao

Okuda

Minami

et al. 1992

Zeitschrift Für Naturforschung A

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“…This motion is likely a wobbling of the phenyltrimethylphosphonium cation, with the amplitude of the motion increasing with temperature. At the highest attainable temperature in methylammonium salts (28,29). At temperatures between 343 and 432 K effective x values ranging from 159 to 146 kHz were employed.…”

Section: Phetzyltrimethylphosphonium-d3 Iodide (6)mentioning

confidence: 99%

A deuterium NMR study of molecular dynamics and geometry in two classes of onium salts: (CH₃)₃E⁺X⁻ and C₆H₅M(CH₃)₃⁺I⁻

Penner¹,

Polson²,

Daleman³

et al. 1993

Can. J. Chem.

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Deuterium NMR measurements are reported for two types of onium salts: (CH,),E+I-, where E = 0 (counterion is BF,-), S, Se, or Te, and C6HSM(CH3),+I-, where M = N, P, or As. Within each class of compounds the activation energy for rotation of the trimethyl groups about the C; axis increases with increasing size of the central atom. In the first class of compounds the C-E-C bond angle decreases with the size of the atom E. In addition the magnitude of the quadrupolar coupling constant, X , varies with E, ranging from 160 kHz for E = 0 to 190 kHz for E = Te. This is in qualitative agreement with molecular orbital calculations of the electric field gradients. At low temperatures the ' H NMR spectrum of C,H5N(CH3),+I-can only be rationalized with a model in which trimethyl rotation is faster than methyl rotation. The %I NMR of ring (predominantly ortho and para)-deuterated C6H5N(CH,),+I is consistent with rapid rz-site (rz 2 3) rotation of the phenyl ring above 390 K. Below 390 K spectra characteristic of two-site, 18O0, flips of the phenyl ring are observed. Below 280 K the motion of the phenyl ring is in the rigid lattice limit. Chem. 71,417 (1993). On a effectuk des mesures de RMN du deuterium pour deux types de sels onium : (CH3)3E+I-dans lesquels E = 0 (le contre-ion est le BFJ, S, Se ou Te, et C,H5M(CH3), dans lesquels M = N, P ou As. Dans chacune de ces classes de composes, I'energie d'activation de la rotation des groupes mkthyles autour de l'axe C; augmente avec une augmentation de la taille de I'atome central. Dans la premiere classe de composes, l'angle de la llaison C-E-C augmente avec une augmentation de la taille de l'atome E. De plus, l'amplitude de la constante de couplage quadripolaire, X, varie avec E; elle varie de 160 kHz pour E = 0 a 190 kHz pour E Te. Ce resultat est en accord qualitatif avec les calculs d'orbitales molkculaires des gradients des champs klectriques. A basses tem$ratures, on ne peut rationaliser les spectres RMN du ' H du C6HSN(CH3)3fI-qu'a I'aide d'un modele dans lequel la rotation de trimethyle est plus rapide que celle du methyle. Le spectre RMN du %I du cycle C,H5N(CH3),+1-deutCrC (principalement en ortho et para) est en accord avec la rotation rapide de n-sites (rz 2 3) du cycle phknyle B des temperatures supkrieures a 390 K. A des tempkratures inferieures B 390 K, on observe des spectres caractkristiques de rotations rapides des noyaux phknyles sur deux sites, 180". En-dessous de 280 K, les dkplacements du noyau phenyle se font dans les limites d'un reseau rigide.[Traduit par la redaction]

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