Structural change in (C5H5NH)SbBr4 with temperature

Abstract

730, J a p a n ) Summary 8lBr N.q.r. spectroscopy has revealed a drastic structural change in the (C,H,NH)SbBr, crystal; above 253 K the SbBr,-anion has the trigonal bipyramid structure, whereas below 253 K the axial bonds become asymmetric and the SbBr,-anion is more reasonably described as SbBr,-Br-a t 77 K.

Reconstructive Phase Transformation and Kinetics of Cs3Sb2I9by Means of Rietveld Analysis of X-Ray Diffraction and127I NQR

“…This is mainly due to the occurrence of the hypervalence for Sb(III); i.e., the three-center four-electron bond is formed at the trans X-Sb-X. A typical example is C H NHSbBr , in which it was reported that the symmetric trans Br-Sb-Br bond deformed to Br-Sb2Br\ below the second-order phase transition at ¹ "253 K. The anion structure in C H NHSbBr was described more appropriately as SbBr ) Br\ at 77 K (4,5). The physical properties of these antimony halides have recently been studied vigorously.…”

“…Values for n determined from the slope of the straight lines were 1.30$0.15 and 1.34$0.15 by means of the X-ray diffraction and NQR, respectively. For the process controlled by diffusion, the exponent n is sum of two contributions, n" # /2, [4] where is an exponent of nucleation rate behavior and is a growth dimension (1, 2, or 3) (24). As the product phase has a layered structure, the present transformation with n"1.3-1.34 seems to be controlled by either one-or twodimensional growth of nuclei with 0( (1.…”

127I NQR and 1H NMR studies of 4-aminopyridinium tetraiodoantimonate(III); molecular motion and phase transition

“…The resonance lines in the respective phases are divided into two groups being separated widely in frequency: Two high-and two low-frequency lines exist around 136 and 114 MHz, respectively in the β-phase, and one high-and one low-frequency lines around 144 and 112 MHz, respectively in the α(II)-phase. These spectrum patterns are well along with those in PyHSbBr 4[4], 4-NH 2 PyHSbBr 4[2], PyHSbCl 4[7], and 4-NH 2 PyHBiBr 4 ·H 2 O[9]. Though the crystal structures of any phases of 4-NH 2 PyHSbI4 have not yet been clarified, their 127 I NQR spectra thus indicate that there may exist one-dimensional infinitive chain structures…”

“…Okuda et al [4] have found that the crystals of PyHSbBr 4 (Py = C 5 H 5 N) undergo a characteristic phase transition at 253 K. In the low temperature phase (LTP), the respective pairs of the 81 Br NQR lines of terminal and bridging Br atoms, which are split up and down in frequency from each line in the room temperature phase (RTP), increase enormously the frequency splitting between each pair with decreasing temperatures. Yamada et al [5] have investigated the temperature dependence of the crystal structures and 2 H NMR spectra of this compound.…”

Crystal Structure and Phase Transition of 4-Aminopyridinium Tetrabromoantimonate(III) as Studied by Bromine and Antimony NQR, Proton NMR, and Single Crystal X-Ray Diffraction

“…The reorientation in the LTP seems to be rapidly switched into the reorientation in the RTP in the vicinity of T c . The solid and broken curves in the RTP are calculated by (1) and (2) with E a = 25.9 kJ/mol, r 0 = 5.88xl0-15 s, C = 1.92xl0 9 s~2. The solid curve is in good agreement with the experimental results.…”