Excitation dynamics in solutions, films and crystals of indandione-1,3 pyridinium betaine

The excitation decay kinetics of polar Indandione-1,3 Pyridinium Betaine (L PB) molecules in various environments: solvents, films and crystals, were s tudied using time-resolved luminescence and transient absorption measuremen ts. A red-shift, depolarization and fast decay of the luminescence intensit y were observed on a femtosecond time scale in dilute solutions and explain ed by excitation relaxation from the initially created intramolecular charg e transfer state to the lower energy excited state of the indandione moiety . The first fast relaxation stage is followed by a slower one responsible f or the relaxation to the ground state stage with the rate depending on the viscosity of the surrounding. By comparing the excitation properties of IPB in solution and those in the crystal form, the influence of the intermolec ular interactions on the excited state dynamics is revealed. Excitation rel axation in the IPB deposited films of different thickness and in a single c rystal is described as a competition between different relaxation paths of nonradiative recombination, these paths being the high lying Frenkel excito n states and the low lying intermolecular charge transfer states.