S2O2分子稳定结构的密度泛函理论研究

采用密度泛函理论中的B3LYP方法,在6-311+G(3df)和Aug-cc-pVTZ水平上,研究了单态S2O2分子的各种可能的异构体及其相对稳定性。结果表明,具有C2v对称性的三角平面分叉异构体的热力学稳定性要高于目前实验上唯一被发现的具有C2v对称性的cis-OSSO异构体,同时trans-OSSO的稳定性与顺式异构体十分接近,这2种异构体应该可以在实验上被观察到。同时本文还讨论了3个最稳定构型的前线分子轨道和链型OSSO的内扭转势能。

DFT Study on the Stabilities of Disulfur Dioxide Isomers

The ground state isomers of S2O2 have been studied by using the B3LYP method of density functional theory (DFT) with the 6-311+G(3df) and Aug-cc-pVTZ basis set levels. All geometries were fully optimized. The stable structures were identified by the calculation of frequencies. The three stable isomers of trigonal planar S=SO2, cis-OSSO and trans-OSSO were obtained. Though only the cis-planar structure has been observed experimentally, the present calculations suggest that the trigonal form with similar structure to the sulfur trioxide is more stable than cis-planar OSSO (lower 9.1 kJ穖ol-1 corrected with zero-point vibrational energy at the B3LYP/Aug-cc-pVTZ level). The total energy of trans-planar OSSO is also very close to the corresponding cis form and lower than that for trans form by 11.5 kJ穖ol-1 at the B3LYP/Aug-cc-pVTZ level. The internal torsional potential energy of chain OSSO and frontier molecular orbitals of the three most stable isomers are discussed in this paper.