An infrared and Raman study of the phase transitions and the torsional barrier in hydrazonium sulfate, N2H6SO4

Abstract

Infrared and Raman spectra of N2H6SO4 have been investigated through the phase transitions at 230 K (III-II) and 483 K (II-I) and assignments made to the various vibrational modes. The assignments have been confirmed by studies of the deuterated compound. The internal modes of both N2H62+ and SO42− ions show marked changes across the phase transitions. The torsional mode of N2H62+ with a fundamental frequency of 517 cm−1 in the room-temperature phase II, disappears in the high-temperature phase, I, accompanied by the appearance of the vq bending mode at 845 cm−1. The torsional barrier is estimated to be ≈32 kJ mol−1. The hydrazonium ion in the high-temperature phase is comparable to ethane. The SO42− ion bands also show marked changes across the phase transitions, the v1 and v2 bands disappearing in the high-temperature phase. In the low-temperature phase, III, both molecular ions are more distorted than in the room-temperature phase.