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

Abstract

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.

81Br NQR and Crystal Structure of Ethylammonium Tribromomercurate(II), CH3CH2NH3HgBr3

“…The frequency shifts produced by deuteration are similar to those observed in (C H 3N H 3)2HgBr4 [6], showing a small difference. From qualitative consider ations [6] .1°, the shifts of v2 are also positive at high temperatures, but in contradiction to the above pre diction their values tend to increase with decreasing temperature.…”

“…From qualitative consider ations [6] .1°, the shifts of v2 are also positive at high temperatures, but in contradiction to the above pre diction their values tend to increase with decreasing temperature. Further, for v1?…”

“…The assignment < -+ Br(j) is done by qualita tive arguments and is tentative. This may show that the electron populations of px or py may be effectively reduced by these intermolecular bonds, which may result in the large decrease of reso nance frequencies [6].…”

“…[5] who observed phase transitions in both systems and compared the room tem perature struc ture of both com pounds [4] with the N Q R results. (CH 3N H 3)2HgBr4 (and (C H 3N D 3)2H gBr4) and (CH 3N H 3)2H gI4 have been studied by 81Br and 127I NQR, respectively, as a function of tem perature by Terao et al [6] and discussed in com parison with the crystal structure of the com pounds [7] and their lattice dynamics [8].…”

Phase Transition and Crystal Dynamics of 4-Bromobenzyl Alcohol

“…The 81 Br and 35 C1 NQR spectra were detected by a home made super-regenerative oscillator detector [3] and by a conventional pulsed NQR spectrometer [4], respectively. The accuracy of the frequency measurement was 20 and 0.5 kHz, for the Br and CT <u CI NQR, respectively.…”