Spectroscopic Studies of Fluorenone Derivatives

The absorption and steady-state fluorescence spectra of fluorenone, 1-hydroxyfluorenone, and 3-dimethylaminofluorenone have been obtained for various concentrations in a series of non-polar and polar solvents. The substituents (-OH and -N(CH₃)₂) as the electron-donating functional groups cause a large shift of the longwave absorption band and Stokes' shift of the monomer- and excimer-fluorescence bands in comparison with fluorenone. The total emission spectrum of 3-dimethylaminoflourenone in polar aprotic solvents exhibits a new band at 500 nm originating form the emission of the twisted intramolecular charge transfer (TICT) isomer. The excited state dipole moments of the emiting species of the molecule studied are determined using the solvatation shift method and calculated values of the ground state dipole moments.