SUPERSONIC JET STUDIES OF FLUORENE CLUSTERED WITH WATER, AMMONIA, AND PIPERIDINE

Mass-resolved excitation spectroscopy and dispersed emission spectroscopy are employed to study van der Waals (vdW) clusters of jet-cooled fluorene with ammonia, water, and piperidine. For fluorene(H2O)1 and fluorene(NH3)1 clusters, cluster geometries and binding energies can be suggested based on the experimental results and Lennard-Jones (LG) potential (6-12-1) energy calculations. As the number of solvent molecules in the cluster is increased, spectra of the clusters become more complex and broad probably due to the many possible stable configurations for these vdW clusters. Although the pKa for fluorene in its first excited singlet state (Förster cycle calculations) is quite acidic (-8.6), and solvent molecules can coordinate to the aliphatic hydrogens of the fluorene molecule in at least some cluster configurations, no direct evidence is found for the occurrence of proton transfer in S1 in these systems. © 1990 American Chemical Society.