Conformational stability of tetrafluorohydrazine, N2F4

The far infrared (60-350 cm(-1)) and low-frequency Raman (80-150 cm(-1)) spectra of gaseous tetrafluorohydrazine, N2F4, have been recorded. The fundamental and several excited state transitions of the torsional mode of the gauche conformer have been observed in both spectra. Variable-temperature (-60 to -90 degrees C) studies of the infrared spectra of N2F4 dissolved in liquid xenon have been recorded. From these data the enthalpy difference has been determined to be 69 +/- 6 cm(-1) (197 +/- 17 cal/mol), with the trans conformer the more stable rotamer. Ab initio calculations have been carried out with several different basis sets up to MP2/6-311++G* from which the structural parameters, conformational stability, harmonic force constants, and infrared and Raman spectra have been obtained. These quantities have been compared to the experimental values when appropriate. Some of the fundamentals have been reassigned, and the potential function governing the conformer interchange has been determined. The results are compared to the corresponding results from some similar molecules.