1. C[sub 4]N: The first C[sub n]N radical with stable cyclic isomers.
- Author
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Ding, Yi-hong, Liu, Jin-long, Huang, Xu-ri, Li, Ze-sheng, and Sun, Chia-chung
- Subjects
CARBON compounds ,POTENTIAL energy surfaces - Abstract
The potential-energy surface of the interstellar molecule C[sub 4]N is explored at the B3LYP/6-311G(d) level of theory. Thirteen isomers including the linear, three-membered ring, four-membered ring, A-like, Y-like, and cage-like structures are located as minima connected by 23 interconversion transition states. The structures of the most relevant isomers and transition states are further optimized at the QCISD/6-311G(d) level followed by single-point energy calculations at the MP4SDTQ, CCSD(T), and QCISD(T) levels with the 6-311G(2df) basis set. At the CCSD(T)/6-311G(2df)//QCISD/6-311G(d) level, the lowest-lying isomer is a linear structure CCCCN 1 followed by a CCC three-membered ring structure 4 with exocyclic CCN bonding that lies only 2.8 kcal/mol higher. The third and fourth low-lying isomers possess a CCC three-membered ring structure 5 with exocyclic CNC bonding at 21.4 kcal/mol and a linear structure CCCNC 2 at 23.4 kcal/mol, respectively. All the four isomers 1, 2, 4, and 5 and another high-lying isomer 3 with a linear CCNCC structure at 62.5 kcal/mol are shown to have considerable kinetic stability towards isomerization and dissociation. Thus, all the five isomers may be experimentally observable. Possible formation of these five stable C[sub 4]N isomers in interstellar space is discussed. Finally, our calculations show that the Møller-Plesset methods fail to predict even qualitatively the energetic properties between the four low-lying isomers 1, 2, 4, and 5, in comparison with the QCISD and CCSD results. This paper indicates that C[sub 4]N may be the first interstellar molecule with stable low-lying cyclic isomers among the C[sub n]N radical series to be detectable in near future. The results presented in this paper may provide useful information for future laboratory and interstellar identification of various C[sub 4]N isomers. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]
- Published
- 2001
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