Vibrational spectra and density functional study of propylgermane

Raman and infrared spectra of propylgermane, CH3CH2CH2GeH3, and its Ge-deuterated analog, CH3CH2CH2GeD3, were investigated in their gaseous, liquid and solid states. The normal coordinate treatment was carried out by density functional theory (DFT) calculation, using B3LYP/6-31G* and 6-311++G** basis sets, and the corresponding fundamental vibrations were assigned. The trans (T) and gauche (G) forms around the central C-C bond coexisted in the gaseous and liquid states and only the T form existed in the solid state. From the temperature dependent measurements of the Raman spectra in the liquid state, the enthalpy difference was found to be DeltaH(T - G) = -0.36 +/- 0.02 kcal mol(-1) with the T form being more stable. The energy differences between the isomers obtained by DFT calculations were DeltaE(T - G) = -0.46 kcal mol(-1) and DeltaE(T - G) = -0.87 kcal mol(-1) by the 6-31G* basis set and 6-311++G** basis set, respectively. (C) 2002 Elsevier Science B.V. All rights reserved.