Vibrational study of phase transitions in (C3H7NH3)2PbCl4

✍ Scribed by Younes Abid; M. Kamoun; A. Daoud; F. Romain

• Publisher: John Wiley and Sons
• Year: 1990
• Tongue: English
• Weight: 407 KB
• Volume: 21
• Category: Article
• ISSN: 0377-0486
• DOI: 10.1002/jrs.1250211103

✦ Synopsis

Abstract

Infrared and Raman spectra (5–3500 cm^−1^) of polycrystalline samples of (C~3~H~7~NH~3~)~2~PbCl~4~ and of its deuterated derivative were investigated in the temperature range 90–300 K. An assignment of the observed bands at room temperature is proposed. A temperature dependence study of the frequencies, ν, and half‐widths, Δν~1/2~, of some low‐frequency Raman bands revealed two phase transitions at about 110 and 170 K, whereas the deuterated compound showed only one phase transition at about 150 K in the same temperature range. These transitions are believed to be governed by libration of the cation coupled with NH~3~ group jumps between different potential wells. The value of activation energy, E~0~ = 3.2 kJ mol^−1^, was calculated from the plot of Δν~1/2~ ν__s.__ temperature; it is of the same order of magnitude as the potential barrier, V~6~ = 3.53 kJ mol^−1^, calculated from the torsional frequency of NH~3~^+^ (288 cm^−1^).