Aggregation Behavior and Electron-Transfer Reaction of Dendritic Perylene Bisimide, Accompanied by the Formation of Highly Stable Anionic Radical Species

Graphical A colorful exchange : A neutral, water-soluble, PEG-substituted perylene bisimide (PEPBI) was synthesized and its concentration-, solvent- and temperature-dependent visible and fluorescence spectra were measured. PEPBI exists as a dimer in aqueous solution but can be dispersed as monomers with an anionic surfactant. In organic solvents the monomer predominates. The reduction of PEPBI and the resulting aggregate forms was also investigated. A polyethylene-glycol-functionalized perylene bisimide (PEPBI) was synthesized. Its concentration-, solvent- and temperature-dependent visible spectra were measured and its aggregation states were analyzed. PEPBI exists as an aggregate dimer in aqueous solution or predominantly as a monomer in organic solvents. The anionic surfactant sodium dodecylbenzenesulfonate (SDBS) can disperse PEPBI as a monomer in aqueous solution. The fluorescence of these solutions depends on the concentration of PEPBI and SDBS. The reduction of aggregated PEPBI with Na 2 S is slow and the monoanion radical as well as dianion species are the main forms of monomer. PEPBI exists predominantly as monomers in DMF and reacts with Na 2 S much faster. Interestingly, the anionic radical species exist in H-aggregate form at low PEPBI concentrations and J-aggregation occurs at high concentration. The dianion species is EPR-silent and its color highly depends on its concentration in DMF.