SUBSTITUENT EFFECTS ON CARBANION PHOTOPHYSICS - 9-ARYLFLUORENYL ANIONS

In an attempt to better understand the photophysics of resonance-stabilized carbanions, substituent effects on the excited-state properties of 9-arylfluorenyl anions have been examined. These properties include excited-state lifetimes, quenching rate constants, fluorescence quantum yields and rate constants, and radiationless decay rate constants. While the resultant data reveal a parallel between excited-state lifetime and the energy of the pi* orbital associated with the substituents obtained by electron transmission spectroscopy, time-resolved picosecond absorption spectroscopy fails to indicate the presence of an intramolecular charge-transfer state. The excited-state lifetimes can be rationalized by an appeal to the energy gap law, relating the nonradiative decay rate to the energy difference between the first excited state and the ground state.