Low-Lying Triplet States of Diphosphene and Diphosphinylidene

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• 作者：Tongxiang Lu ; Qiang Hao ; Andrew C. Simmonett ; Francesco A. Evangelista ; Yukio Yamaguchi ; De-Cai Fang ; Henry F. Schaefer ; III
• 刊名：Journal of Physical Chemistry A
• 出版年：2010
• 出版时间：October 14, 2010
• 年：2010
• 卷：114
• 期：40
• 页码：10850-10856
• 全文大小：226K
• 年卷期：v.114,no.40(October 14, 2010)
• ISSN：1520-5215

文摘

In this research, six low-lying triplet states of diphosphene (HPPH) and disphosphinylidene (PPH₂) are systematically investigated starting from self-consistent field theory and proceeding to multireference coupled cluster methods using a wide range of basis sets. For each structure, the geometry, energy, dipole moment, harmonic vibrational frequencies, and infrared intensities are predicted. The triplet potential energy surface (PES) of P₂H₂ is presented, based on systematically extrapolated coupled cluster energies and accounting for core−valence correlation, zero-point vibrational energy, and diagonal Born−Oppenheimer effects. Both ³A′′ pyramidal PPH₂ and ³B skewed HPPH are minima on the triplet PES and lie 27.4 ± 0.3 and 32.4 ± 0.3 kcal mol⁻¹ above the global minimum structure closed-shell ¹A_g trans-HPPH, respectively. The energy barrier for the isomerization reaction [³B skewed HPPH → ³A′′ pyramidal PPH₂] is predicted to be 16.4 ± 0.3 kcal mol⁻¹. On this triplet PES, two equivalent ³B skewed HPPH are converted via the ³B_u trans-HPPH transition state with a barrier of 9.1 ± 0.3 kcal mol⁻¹ or via the ³B₂ cis-HPPH transition state with a barrier of 11.1 ± 0.3 kcal mol⁻¹. Moreover, the two equivalent ³A′′ pyramidal PPH₂ structures are connected through the ³A₂ planar PPH₂ transition state with a barrier of 18.6 ± 0.3 kcal mol⁻¹. The energy crossing of the singlet and triplet adiabatic PES is studied using Mukherjee multireference coupled cluster method with the cc-pVQZ basis set, which predicts that the ³B skewed HPPH is 1.4 kcal mol⁻¹ lower in energy than the corresponding ¹A skewed HPPH at the ³B skewed HPPH optimized geometry.