Structure of hydrogen fluoride complexes with diethylketone in a HF–Et2CO solution

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The optimal configurations and the vibrational spectra of heteroassociates (HAs) of hydrogen fluoride and diethylketone molecules with 1:1, 2:2, 4:1, and 8:2 compositions are calculated using the density functional theory (B3LYP/6-31++G(d,p)). A comparison of the results of calculations and the known experimental data reveal that the following stable hydrogen-bonded molecular complexes are formed in HF–Et2CO solutions: the C2h symmetry cyclic heterotetramer (HF)2∙(Et2CO)2 and the tricyclic HA (HF)8∙(Et2CO)2 formed based on the heterotetramer by the binding of two (HF)3 moieties. It is shown that it is appropriate to decompose the spectral curve into the Gaussian functions or the Lorentzian functions to determine the frequencies and the integrated intensities of broad and overlapped IR bands. The first type of the decomposition enables one to estimate more correctly the values of the band frequencies, and the second type makes it possible to find more correctly the band intensities.