Fulvalenes
Fulvalenes are a class of non-benzenoid hydrocarbons composed of two cyclopentadiene rings connected by a single exocyclic double bond. The general formula for fulvalenes is C2nH2n, where 'n' represents the number of carbon atoms in each ring (in the case of fulvalene itself, n=5). The parent fulvalene, also called bicyclopentadienylidene, has the formula C10H8.
Fulvalenes are of interest due to their unique electronic structures and potential for exhibiting interesting properties, such as high dipole moments. The extent of charge separation between the two rings can vary depending on the substituents present on the rings. Unsubstituted fulvalene, however, is predicted to have only a small dipole moment.
Derivatives of fulvalenes can be prepared with various substituents on the cyclopentadiene rings, leading to a wide range of compounds with diverse properties. These modifications can influence the electronic structure, stability, and reactivity of the fulvalene system.
The synthesis of fulvalenes often involves condensation reactions of substituted cyclopentadienes or related compounds. The stability of fulvalenes is influenced by the substituents present and the reaction conditions used during their formation.
Fulvalenes have found applications in various areas of chemistry, including materials science, where they are used as building blocks for the construction of organic materials with novel electronic and optical properties. They are also used in organometallic chemistry as ligands for transition metals.