Switching the Spin State of Diphenylcarbene via Halogen Bonding

详细信息    查看全文

• 作者：Stefan Henkel ; Paolo Costa ; Linda Klute ; Pandian Sokkar ; Miguel Fernandez-Oliva ; Walter Thiel ; Elsa Sanchez-Garcia ; Wolfram Sander
• 刊名：Journal of the American Chemical Society
• 出版年：2016
• 出版时间：February 10, 2016
• 年：2016
• 卷：138
• 期：5
• 页码：1689-1697
• 全文大小：544K
• ISSN：1520-5126

文摘

The interactions between diphenylcarbene DPC and the halogen bond donors CF₃I and CF₃Br were investigated using matrix isolation spectroscopy (IR, UV–vis, and EPR) in combination with QM and QM/MM calculations. Both halogen bond donors CF₃X form very strong complexes with the singlet state of DPC, but only weakly interact with triplet DPC. This results in a switching of the spin state of DPC, the singlet complexes becoming more stable than the triplet complexes. CF₃I forms a second complex (type II) with DPC that is thermodynamically slightly more stable. Calculations predict that in this second complex the DPC···I distance is shorter than the F₃C···I distance, whereas in the first (type I) complex the DPC···I distance is, as expected, longer. CF₃Br only forms the type I complex. Upon irradiation I or Br, respectively, are transferred to the DPC carbene center and radical pairs are formed. Finally, on annealing, the formal C–X insertion product of DPC is observed. Thus, halogen bonding is a powerful new principle to control the spin state of reactive carbenes.