Two bands at xA cm

Note that the frequencies of the bands arising from the stretching vibrations of CF3 group in PyHOTf are in reverse order with respect to the general expectation; 'GW788388' i.e. usually a band due to the asymmetric stretching vibration of this group is expected to have a higher frequency than that due to its symmetric vibration [24]. The reversible order of the stretching frequencies of the CF3 group in triflatic anion in solid state was explained by Huang et al. [9] by “indirect interaction of the sulfur atom with the fluorine or oxygen atoms”.