Ab initio study of the singlet–triplet relative stability of 2,6-dibromo-2′,6′-bistrifluoromethyl-diphenylmethylene
- 作者：Rodrí ; guez ; Elena ; Caballol ; Rosa ; Reguero ; Mar
- 关键词：Diphenylcarbene ; Singlet&ndash ; triplet relative stability ; Correlated ab initio calculation
- 刊名：Chemical Physics
- 出版年：2004
- 期刊代码：18_03010104
- 类别：ch
- 出版时间：August 2, 2004
- 卷：303
- 期：1-2
- 页码：157-164
- 文件大小：235 K
摘要
Diphenylmethylene is the main parent system in the search of stable carbenes, singlet as well as triplet ones. The substituents of the phenyl rings are the keys to favour one state in front of the other, but the mechanism of this influence is little known. A model of one of the first stable triplet carbenes that has been synthesized, the 2,6-dibromo-2′,6′-bistrifluoromethyl-diphenylmethylene, has been the subject of this theoretical study. Singlet–triplet energy differences have been calculated using high level ab initio methods (CASSCF for optimum geometries and DDCI for vertical energy differences and CASPT2 and B3LYP-Broken Symmetry for comparison purposes). For the model carbene the results showed that the triplet state, with a large carbenic angle, was more stable than the singlet one. Two additional series of calculations have been carried out to analyze the electronic and steric influence of the phenyls and the phenyl substituents on the singlet–triplet relative stability.