title: Definitive evidence for the contribution of biradical character in a closed-shell molecule, derivative of 1,4-bis-(4,5-diphenylimidazol-2-ylidene)cyclohexa-2,5-diene.
abstract: This study provides conclusive proof that the thermally excited open-shell state with biradical character is contributing to the ground state of a closed-shell molecule, tF-BDPI-2Y, where four hydrogen atoms at the central phenylene ring are substituted with four fluorine atoms of 1,4-bis-(4,5-diphenylimidazol-2-ylidene)cyclohexa-2,5-diene (BDPI-2Y). A small increase in the population of biradical species of tF-BDPI-2Y results in the formation of the dimer form by the radical recombination reaction. Controlling the equilibrium between a closed-shell diamagnetic-quinoid state and an open-shell paramagnetic-biradical state will provide significant progress in the field of pi-conjugated delocalized biradical chemistry.
authors.affiliation: Department of Chemistry, School of Science and Engineering, Aoyama Gakuin University, and The 21st Century COE Program, 5-10-1 Fuchinobe, Sagamihara, Kanagawa 229-8558, Japan.
authors.forename: Azusa
authors.initials: A
authors.lastname: Kikuchi
authors.forename: Fumiyasu
authors.initials: F
authors.lastname: Iwahori
authors.forename: Jiro
authors.initials: J
authors.lastname: Abe