Na+ concentration dependence of intermolecular distance in 3,4,9,10-perylenetetracarboxylic dianhydride dimer

We have discussed the Na+ concentration dependence of the intermolecular distance of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) dimers in aqueous solution of NaOH. We have particularly focused on the S 1 0 – S 0 0 transition of the PTCDA dimers which is sensitive to the intermolecular distance and we have found that the S 1 0 state is split for the higher lying sublevel and the lower lying sublevel with the increase of the Na+ concentrations. From the energy shift of the lower lying sublevel, we have estimated the intermolecular distance of the PTCDA dimer, that changes from 7.5 to 4.9 Å by the Na+ concentration.