Conformational analysis and vibrational assignment of bis-gem-diol of hexafluoroacetylacetone

A complete conformational analysis of doubly-hydrated hexafluoroacetylacetone, 1,1,1,5,5,5-hexafluoropentane-2,2,4,4-tetraol (HFPTO), was carried out by ab initio calculations, at the density functional theory (DFT) level. According to our calculations, 10 stable conformers were obtained. The most stable conformer is stabilized by formation of two intramolecular hydrogen bond (of OHO type) in opposite directions. The calculated geometrical parameters are in agreement with the corresponding values obtained by X-ray diffraction technique. Harmonic and anharmonic vibrational frequencies of the most stable conformer and its deuterated analogue were also calculated and compared with the experimental data. Additionally the Bader theory is applied here showing that characteristics of the bond critical points (BCPs) are useful parameters to estimate the strength of intramolecular hydrogen bonding. Natural bond orbital (NBO) analysis method was performed for the investigation of the relative stability of HFPTO conformers.