Novel 1,5-difluoropenta-1,4-diyn-3-one, its sulfur and selenium analogues: MP2 and DFT gas phase study of their molecular structures and vibrational spectra

1,5-Difluoropenta-1,4-diyne-3-one, its sulfur and selenium analogues in C2v symmetry have been studied in the gas phase by ab initio MP2 and B3LYP methods. The basis set employed for these methods is 6-311++G(d,p) for all atoms. Molecular parameters, namely bond lengths, bond angles, rotational constants, dipole moments and energies, and vibrational infrared spectra parameters, namely harmonic vibrational frequencies and absolute intensities are predicted for these difluoroketones. Atomisation energies and natural charges on the atoms have also been predicted. The molecular parameters and vibrational spectra of the parent ketone namely, penta-1,4-diyn-3-one [Y. Umar, J. Mol. Struct. (THEOCHEM) 728 (2005) 111-115], have been calculated at the same levels of theory and basis set employed in this study. The results obtained are in good agreement with available experimental literature data. Therefore, data from the present study are expected to be valid for the molecular structures and vibrational spectra of the novel difluoroketones. This work also compares the effect on molecular and vibrational parameters of penta-1,4-diyn-3-one, its sulfur and selenium analogues when hydrogen is substituted by fluorine.