Winkler Michael
Institut für Organische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany.
J Phys Chem A. 2008 Sep 18;112(37):8649-53. doi: 10.1021/jp802547c. Epub 2008 Aug 21.
The vertical and adiabatic singlet-triplet energy splittings (Delta E ST) of phenylnitrene were computed by a variety of multireference configuration interaction and perturbation theory methods employing basis sets of up to quadruple-xi quality and extrapolation to the complete basis set limit. The vertical and adiabatic energy gaps are 18.9 and 15.9 kcal mol (-1), respectively, the latter in reasonable agreement with the revised experimental value of 15.1 +/- 0.2 kcal mol (-1). The energy difference between both states at the geometry of the a (1)A 2 singlet state was also considered and amounts to 13.8 kcal mol (-1). In obtaining accurate state energy splittings, basis set completeness turns out to be a more important issue than the level of dynamical electron correlation treatment. Density functional theory that is frequently employed to investigate phenylnitrenes and their rearrangements yields varying results and, depending on the functional, gives adiabatic energy differences between 9 and 16 kcal mol (-1). The b (1)A 1 state has a similar geometry as the ground state of 1 and is 31 kcal mol (-1) higher in energy. According to best estimates, the next higher singlet states, c (1)A 1 and d (1)B 1, are 57 and 72 kcal mol (-1) above the ground state. In the triplet manifold, vertical excitation energies to the A (3)B 1 and B (3)A 2 states are 71 and 77 kcal mol (-1), respectively.
通过多种多参考组态相互作用和微扰理论方法，采用高达四重ζ质量的基组并外推至完备基组极限，计算了苯炔的垂直和绝热单重态-三重态能量分裂（ΔE ST）。垂直和绝热能隙分别为18.9和15.9 kcal·mol⁻¹，后者与修正后的实验值15.1±0.2 kcal·mol⁻¹合理吻合。还考虑了在a (¹A₂)单重态几何结构下两个态之间的能量差，其值为13.8 kcal·mol⁻¹。在获得精确的态能量分裂时，基组完备性比动态电子相关处理水平更为重要。常用于研究苯炔及其重排的密度泛函理论给出了不同的结果，根据所使用的泛函，绝热能量差在9至16 kcal·mol⁻¹之间。b (¹A₁)态的几何结构与1的基态相似，能量高31 kcal·mol⁻¹。据最佳估计，次高的单重态c (¹A₁)和d (¹B₁)比基态分别高57和72 kcal·mol⁻¹。在三重态中，到A (³B₁)和B (³A₂)态的垂直激发能分别为71和77 kcal·mol⁻¹。
