Anharmonic Vibrational Analysis for the Propadienylidene Molecule (H2C═C═C:)

详细信息    查看全文

• 作者：Qunyan Wu ; Qiang Hao ; Jeremiah J. Wilke ; Andrew C. Simmonett ; Yukio Yamaguchi ; Qianshu Li ; De-Cai Fang ; Henry F. Schaefer ; III
• 刊名：Journal of Chemical Theory and Computation
• 出版年：2010
• 出版时间：October 12, 2010
• 年：2010
• 卷：6
• 期：10
• 页码：3122-3130
• 全文大小：177K
• 年卷期：v.6,no.10(October 12, 2010)
• ISSN：1549-9626

文摘

Maier et al. found that photolysis of singlet cyclopropenylidene (1S) in a matrix yields triplet propargylene (2T), which upon further irradiation is converted to singlet propadienylidene (vinylidenecarbene, 3S). Their discovery was followed by interstellar identification of 3S by Cernicharo et al. An accurate quartic force field for propadienylidene (3S) has been determined employing the ab initio coupled-cluster (CC) with single and double excitations and perturbative triple excitations [CCSD(T)] method and the correlation-consistent core−valence quadruple-ζ (cc-pCVQZ) basis set. Utilizing vibrational second-order perturbation theory (VPT2), vibration−rotation coupling constants, rotational constants, centrifugal distortion constants, vibrational anharmonic constants, and fundamental vibrational frequencies are determined. The predicted fundamental frequencies for 3S as well as its ¹³C and deuterium isotopologues are in good agreement with experimental values. The theoretical zero-point vibration corrected rotational constants B₀ are consistent with experimental values within 0.3% of errors. The isotopic shifts of B₀ are in close to exact agreement with experimental observations. The mean absolute deviation between theoretical anharmonic and experimental fundamental vibrational frequencies for 24 modes (excluding CH₂ s-str.) is only 2.6 cm⁻¹. The isotopic shifts of the vibrational frequencies are also in excellent agreement with the available experimental values. However, a large discrepancy is observed for the CH₂ symmetric stretch, casting doubt on the experimental assignment for this mode.