Single crystal vibrational studies of hydrogen bonding in ethylenediammonium chloride

Ethylenediammonium chloride (EDC) single crystal vibrational studies have been performed at room and low temperature as well. The results allowed to get further insight as to the nature of the unusual profile of the NH stretching spectral region. A careful analysis of the infrared spectra in polarized light of the ab and ac crystal faces using the oriented gas model approximation has shown that the absorption profile of the higher frequency region is due mainly to an anharmonic interaction between NH stretching modes and those combination tones which develop parallel transition moments. Single crystal Raman spectra at room and low temperatures (≈10 K) have allowed to localize the peaks of the NH stretching modes. The Raman active lattice mode frequencies were measured at 10 K and 300 K as well. Finally, an almost complete assignment of the internal modes has been reported.