Photochemical and photophysical processes in the molecular cluster of fluorenone

Fluorescence properties of fluorenone and fluorenone molecular clusters with solvent molecules formed in a supersonic free jet expansion were studied. It revealed that fluorenone in the molecular cluster with acetonitrile emits strong fluorescence from its ππ* singlet state while fluorescence from bare fluorenone is very weak. Furthermore, no evidence of intracluster hydrogen abstraction to form ketyl radical in the cluster with 1,4-cyclohexadiene was observed. The fluorenone–ethanol cluster has considerably short lifetime of the S1 state. It could be attributed to the fact that the hydrogen bond in the molecular clusters should accelerate the nonradiative process.