Fluorenylidene
![](/Images/godic/202501/13/Fluorenylidene_Carbene5700.png")
![Intersystem crossing and associated spin-state orbitals of Fluorenylidene.](/Images/godic/202501/13/Intersystem_crossing_of_Fluorenylidene5700.png")
![Synthesis of fluorenylidene from thermolysis or photolysis of 9-diazofluorene
(DAF)](/Images/godic/202501/13/Fluorenylidene_synthesis5700.png")
![Examples of various reaction routes of fluorenylidene in solution](/Images/godic/202501/13/Fluorenylidene_reactions_in_solution5700.png")
9-Fluorenylidene is an aryl carbene derived from the bridging methylene group of fluorene. Fluorenylidene has the unusual property that the triplet ground state is only 1.1 kcal/mol (4.6 kJ/mol) lower in energy than the singlet state. For this reason, fluorenylidene has been studied extensively in organic chemistry.