Conformational studies of the neutral and cation of several substituted fluorenes

The S1 excited state and cation ground state of various fluorene derivatives have been studied experimentally using resonance enhanced multiphoton ionization and zero electron kinetic energy photoelectron spectroscopy. The compounds studied are 2-propylfluorene, 9fluoreneacetic acid and 2-propionylfluorene. Density functional quantum chemical calculations using the GAUSSIAN 98 program have been used to calculate the ground state and cation energies of each conformer as well as the barrier to interconversion via a bond rotation. These calculations, coupled with the experimental results, have led to the identification and assignment of the various conformations of these molecules.