![The PES for the reaction of C6H6 with CP in kcal mol−1 . Values in gray were calculated using CCSD(T)-F12c/cc-pVTZ-F12//ωB97X-2(TQZ)-D3(BJ)/ma-def2-TZVPP, those in orange were found using DFT alone (ωB97X-2(TQZ)-D3(BJ)/ma-def2-TZVPP), and those in navy blue were found using CCSD(T)-F12c/cc-pVTZ-F12//M06-2X-D3(0)/ma-def2-TZVPP. The dashed gray and navy lines corresponds to the identified transition states in the calculations which employed ωB97X-2(TQZ) and M06-2X, respectively. Meanwhile, the dotted black line represents the barrierless CP addition to benzene found from the relaxed scans that used ωB97X, ωB97M, and B2PLYP. -- [astro-ph.GA]](https://i0.wp.com/astrobiology.com/wp-content/uploads/2026/11/A-Potential.png?fit=1200%2C675&ssl=1)
[astro-ph.GA] Quantum chemical computations outline a thermodynamically viable, low-temperature, gas-phase formation pathway for phosphaethynyl cyclopropenylidene (c-C3HCP), resulting from cyclopropenylidene (c-C3H2) and the phosphaethynyl (CP) radical.
Given the detections of both c-C3H2 and the CP radical toward circumstellar shells along with the provided reaction pathway, c-C3HCP is a potentially present astro-molecule which could be searched for in phosphorus rich environments. The reaction of CP and benzene (C6H6) to produce phosphaethynyl benzene (C6H5CP) is also explored.
A marginally emerged, but tentative, transition state is identified for this reaction using certain quantum chemical approaches but not others. Consequently, the formation of CP-substituted benzoid polycyclic aromatic hydrocarbons (PAHs) in astrophysical environments from CP + PAH reactions is possible but currently uncertain.
Additionally, explicitly correlated coupled cluster quartic force field and second-order vibrational perturbation theory rovibrational analysis of the vibrational frequencies and rotational constants of c-C3HCP are provided, as well as density functional theory predictions of the same for CP-benzene (C6H5CP) and both isomers of CP-naphthalene (C10H7CP).
Our results suggest that IR searches for these molecules would likely be unsuccessful due to the low intensities and coincidence with PAH features, but their large dipole moments could make them feasible to detect with radio astronomy.
The barrierless formation of c-C3HCP and possibly barrierless synthesis of C6H5CP stand as examples for future investigations of other CP-substituted aromatic molecules, marking the potential beginning of a new frontier of astronomical aromatic functionalization.
Reace H. J. Willis, Vincent J. Esposito, Thomas H. Speak, Ilsa R. Cooke, Ryan C. Fortenberry
Subjects: Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:2610.30509 [astro-ph.GA] (or arXiv:2610.30509v1 [astro-ph.GA] for this version)
https://doi.org/10.48550/arXiv.2610.30509
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Submission history
From: Reace Willis
[v1] Wed, 21 Oct 2026 22:40:33 UTC (1,630 KB)
https://arxiv.org/abs/2610.30509
Astrobiology, Astronomy, Astrochemistry,
