Energetic and Spectroscopic Properties of the Low-Lying Isomers of C5H: A High-Level Ab Initio Study

Abstract

Fourteen highly reactive isomers of C5H and their ionic counterparts have been theoretically investigated using density functional theory (DFT) and coupled-cluster methods. The linear C5H (l-C5H) radical, pent-1,3-diyn-5-yliden-1-yl (1), along with its cationic form and the cyclic C5H (c-C5H), 1-ethynylcycloprop-1-en-2-yl-3-ylidene (2), have recently been detected in the Taurus Molecular Cloud-1. By using the UCCSD(T)/cc-pCVTZ level of theory, the calculated rotational constants and other spectroscopic parameters are found to be in good agreement with the available experimental data for isomers 1 and 2. Therefore, the current theoretical study may assist synthetic chemists and molecular spectroscopists in detecting other isomers in the laboratory or in the interstellar medium (ISM). Thermodynamically favorable rearrangement schemes for forming low-lying isomers 1, 2, and 3 have also been studied theoretically, and (2λ3-cycloprop-2-en-1-ylidene)ethenylidene (3) with a large dipole moment (μ = 4.73 Debye) is proposed to be a plausible candidate for detection in the ISM.

Energetic and Spectroscopic Properties of Astrophysically Relevant MgC4H Radicals Using High-Level Ab Initio Calculations

“…However, the synthesis, characterization, and eventual identification of such transient species in the laboratory are not a very easy task. Therefore, computational studies on the structure and electronic properties of these astrophysically important molecules may aid the radioastronomers, molecular spectroscopists, and synthetic organic chemists to identify them both in the laboratory as well as in the ISM. ,− Moreover, the spectroscopic detection and identification of these molecules can be challenging due to the presence of the metal atom having many closely spaced electronic states with different spin multiplicities.…”