MgC6H2 Isomers: Potential Candidates for Laboratory and Radioastronomical Studies

Aditya P Pandey; Uday Kumar Padidela; Loganathan Konda Thulasiraman; Ramakrishnan Sethu; Pothiappan Vairaprakash; Venkatesan S Thimmakondu

doi:10.1021/acs.jpca.0c06401

MgC₆H₂ Isomers: Potential Candidates for Laboratory and Radioastronomical Studies

J Phys Chem A. 2020 Sep 17;124(37):7518-7525. doi: 10.1021/acs.jpca.0c06401. Epub 2020 Sep 1.

Authors

Aditya P Pandey^{1

2}, Uday Kumar Padidela², Loganathan Konda Thulasiraman³, Ramakrishnan Sethu⁴, Pothiappan Vairaprakash⁵, Venkatesan S Thimmakondu⁶

Affiliations

¹ Electrical and Computer Engineering, College of Engineering, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, Pennsylvania 15213, United States.
² Department of Chemistry, Birla Institute of Technology and Science, Pilani, K K Birla Goa Campus, Goa - 403 726, India.
³ Department of Chemistry, Alagappa Chettiar Government College of Engineering and Technology, Karaikudi 630 003, Tamil Nadu, India.
⁴ Department of Microbiology, University of Illinois, 601 South Goodwin Avenue, Urbana, Illinois 61801, United States.
⁵ Department of Chemistry, School of Chemical and Biotechnology, SASTRA Deemed University, Thanjavur - 613 401, Tamil Nadu, India.
⁶ Department of Chemistry and Biochemistry, San Diego State University, San Diego, California 92182-1030, United States.

PMID: 32804506
DOI: 10.1021/acs.jpca.0c06401

Abstract

Eighty three stationary points of MgC₆H₂ isomers spanning from 0 to 215 kcal mol^-1 have been theoretically identified using density functional theory at the B3LYP/6-311++G(2d,2p) level of theory. Among them, four low-lying isomers lying within 23.06 kcal mol^-1 (1 eV) have been further characterized in detail using high-level coupled-cluster (CC) methods. The thermodynamically most stable isomer turns out to be 1-magnesacyclohepta-4-en-2,6-diyne (1). The other three isomers, 3-magnesahepta-1,4,6-triyne (2), 1-magnesacyclohepta-2,3,4-trien-6-yne (3), and 1-magnesahepta-2,4,6-triyne (4) lie 8.24, 19.76, and 21.36 kcal mol^-1, respectively, above 1 at the ae-CCSD(T)/cc-pCVTZ level of theory. All the four isomers are polar with a permanent electric dipole moment (μ ≠ 0). Hence, they are potential candidates for rotational spectroscopic studies. Considering the recent identification of magnesium-bearing hydrocarbons such as, MgC₂H and MgC₄H in IRC+10216, it is believed that the current theoretical data may be of relevance to laboratory molecular spectroscopic and radioastronomical studies on MgC₆H₂ isomers. The energetic and spectroscopic information gathered in this study would aid the detection of low-lying MgC₆H₂ isomers in the laboratory, which are indispensable for radioastronomical studies. It is also noted here that neither the National Institute of Standards and Technology Chemistry WebBook nor the Kinetic Database for Astrochemistry lists any isomer of MgC₆H₂ at the moment. Therefore, these isomers are studied here theoretically for the very first time.