Thimmakondu Venkatesan S, Karton Amir
Department of Chemistry, Birla Institute of Technology and Science, Pilani, K K Birla Goa Campus, Goa, 403 726, India.
School of Molecular Sciences, The University of Western Australia, Perth, Western Australia 6009, Australia.
Phys Chem Chem Phys. 2017 Jul 21;19(27):17685-17697. doi: 10.1039/c7cp02848b. Epub 2017 Jul 4.
We use high-level ab initio CCSD(T) and CCSDT(Q) methods to investigate the energetic and spectroscopic properties of nine low-lying isomers of CH, which lie within 1 eV. Among these, heptatriynylidene (1), 1-(buta-1,3-diynyl)cyclopropenylidene (2) and heptahexaenylidene (9) have been detected experimentally. The other six isomers, 1,2-(diethynyl)cyclopropenylidene (3), bicyclo[4.1.0]hepta-1,2,4,5-tetraene-7-ylidene (4), cyclohepta-1,2,3,4-tetraen-6-yne (5), bicyclo[4.1.0]hepta-4,6-diene-2-yne-7-ylidene (6), bicyclo[4.1.0]hepta-1,5-diene-3-yne-7-ylidene (7) and 1-(buta-1,3-diynyl)propadienylidene (8), remain hypothetical to date. Except for 1, all of the isomers are associated with a non-zero dipole moment (μ≠ 0). Although Fourier-transform microwave spectroscopy had detected 2 and 9, our study reveals that six hypothetical isomers (3-8) are thermodynamically sandwiched between the experimentally known and astronomically relevant isomers 2 and 9. The structural parameters, dipole moments, rotational and centrifugal distortion constants, harmonic vibrational frequencies, and infra-red intensities presented here may be useful for the laboratory detection of these previously unidentified isomers (3-8) and also all others (2-9) in astronomical sources.
我们使用高级从头算CCSD(T)和CCSDT(Q)方法来研究CH的九个低能异构体的能量和光谱性质，这些异构体的能量在1电子伏特以内。其中，庚三炔叉（1）、1-（丁-1,3-二炔基）环丙烯叉（2）和庚六烯叉（9）已通过实验检测到。另外六个异构体，1,2-（二乙炔基）环丙烯叉（3）、双环[4.1.0]庚-1,2,4,5-四烯-7-叉（4）、环庚-1,2,3,4-四烯-6-炔（5）、双环[4.1.0]庚-4,6-二烯-2-炔-7-叉（6）、双环[4.1.0]庚-1,5-二烯-3-炔-7-叉（7）和1-（丁-1,3-二炔基）丙二烯叉（8），至今仍是假设的。除了1之外，所有异构体都具有非零偶极矩（μ≠0）。尽管傅里叶变换微波光谱法已检测到2和9，但我们的研究表明，六个假设的异构体（3 - 8）在热力学上夹在实验已知且与天文学相关的异构体2和9之间。这里给出的结构参数、偶极矩、转动和离心畸变常数、简正振动频率以及红外强度，可能有助于在实验室中检测这些先前未识别的异构体（3 - 8）以及天文学源中的所有其他异构体（2 - 9）。
