Fundamental Vibrational Frequencies and Spectroscopic Constants of Substituted Cyclopropenylidene (c-CHX, X = F, Cl, CN).

The recent detection of ethynyl-functionalized cyclopropenylidene (c-CHCH) has initiated the search for other functional forms of cyclopropenylidene (c-CH) in space. There is existing gas-phase rotational spectroscopic data for cyano-cyclopropenylidene (c-CHCN), but the present work provides the first anharmonic vibrational spectral data for that molecule, as well as the first full set of both rotational and vibrational spectroscopic data for fluoro- and chloro-cyclopropenylidenes (c-CHF and c-CHCl). All three molecules have fundamental vibrational frequencies with substantial infrared intensities.