A Small Molecule with PAH Vibrational Properties and a Detectable Rotational Spectrum: c-(C)C 3 H 2 , Cyclopropenylidenyl Carbene

Abstract

The cyclopropenylidenyl carbene, c -(C)C 3 H 2 , should make for an excellent probe of unidentified infrared bands. It has a dipole moment of roughly 5.0 D making it easily detectable rotationally from the ground. Furthermore, it has vibrational frequencies computed here with proven and high-level quantum chemical methods that line up rather well with the typical C−H stretch, C−C stretch, out-of-plane wag, etc., bins delineated for polycyclic aromatic hydrocarbon fundamental frequencies. For instance, the bright C = C stretches are predicted to be at 5.474 and 6.394 μ m, in line with the aromatic infrared bands observed toward various astrophysical regions and within the range of the EXES instrument on board the Stratospheric Observatory for Infrared Astronomy. As a result, potential radioastronomical detection of this molecule could be followed with IR analysis leading to a rare two-pronged analysis for this hydrocarbon, which should shed light onto the nature of currently unattributed IR features.