Negative ion photoelectron spectroscopy of acridine molecular anion and its monohydrate

Negative ion photoelectron spectroscopy was employed to investigate the electronic structure of the acridine molecular anion and its monohydrated anion in the gas phase. Their adiabatic electron affinities were measured to be 0.896±0.010 and 1.18±0.05 eV, and the low-lying electronic excited states in both neutral acridine and in its monohydrate were revealed. The photoelectron spectra clearly exhibit the presence of low-lying singlet and triplet states having a (π, π*) configuration in an uncomplexed acridine molecule. Comparison of the photoelectron spectrum of acridine with that of anthracene shows that photodetachment processes into the excited states of (n, π*) configuration have little intensity, implying a relatively large intramolecular structural relaxation in the (n, π*) states.