Experimental and theoretical studies of monoalkylammonium hexafluorosilicate [CH3(CH2)nNH3]2SiF6 (n = 2, 3) and ethylammonium hexafluorosilicate [(C2H5)2NH2]2SiF6

The infrared spectra of [CH3(CH2)2NH3]2SiF6, [CH3(CH2)3NH3]2SiF6 and [(C2H5)2NH2]2SiF6 compounds, synthesized by us, were recorded at room temperature and discussed. For the butylammonium hexafluorosilicate which crystallized in orthorhombic system with P321 (Z = 1), and ethylammonium hexafluorosilicate crystallizes at room temperature in the monoclinic system with P21 as space group the discussions are made in relation to previously mentioned crystal structures. The vibrational spectra of the cations indicate that they are disordered and hydrogen bonded to the anions. Hydrogen bonding in these compounds is indicated by overtone and combination modes possessing appreciable intensities. The results are compared to density functional theory B3LYP and semi-empirical PM3 calculations. Full thermodynamic properties and geometries are also located and characterized.