title: Bigger and Brighter Fluorenes: Facile π-Expansion, Brilliant Emission and Sensing of Nitroaromatics.
abstract: π-Expanded butterfly-like 2D fluorenes and 3D spirobifluorenes 1-5 were synthesized via a DDQ-mediated oxidative cyclization strategy with a high regioselectivity. Through structural modification via π-expansion, it was possible to achieve near-ultraviolet absorption, bright-blue emission, very high near-unity fluorescence quantum yields in solution as well as in film states, and deep-lying HOMO energy levels with excellent thermal stabilities. Furthermore, these electron-rich compounds displayed a notable behavior towards sensing of nitroaromatic explosives, such as picric acid, up to a detection limit of 0.2 ppb.
authors.affiliation: Department of Chemistry, Indian Institute of Technology Madras, Chennai, 600 036, India.
authors.forename: Jagarapu
authors.initials: J
authors.lastname: Ramakrishna
authors.affiliation: Department of Chemistry, Indian Institute of Technology Madras, Chennai, 600 036, India.
authors.forename: Parthasarathy
authors.initials: P
authors.lastname: Venkatakrishnan
keywords: fluorenes; nitroaromatics; photoluminescence; pi-expansion; sensing