Tuning the photodriven electron transport within the columnar perylenediimide stacks by changing the π-extent of the electron donors

Photodriven electron-transport properties of the self-assemblies of N,N '-di(2-(trimethylammoniumiodide)-ethylene)perylenediimide stacks (TAIPDI)(n) with three electron donors, disodium 4,4 '-bis(2-sulfonatostyryl)-biphenyl (BSSBP, stilbene-420), sodium 9,10-dimethoxyanthracene-2-sulfonate (DANS) and disodium 6-amino-1,3-naphthalenedisulfonate (ANADS) have been studied in water. These electron donors vary in their pi-extent to adjust the electronic coupling and the distance with the PDI stacks. Possessing the largest pi-extent, BSSBP has strong pi-pi interactions as well as ionic interactions with (TAIPDI)(n). Instead of pi-stacking with TAIPDI planes, DANS and ANADS, with a relatively small pi-extent, are embedded in the side chains of TAIPDIs via ionic interactions, resulting in a distance increment from the aromatic TAIPDI cores. After excitation, the BSSBP-(TAIPDI)(n) system exhibits fast charge separation (0.70 ps) and relatively slow charge recombination (485 ps) due to intermolecular electron delocalization along the TAIPDI stacks. On the other hand, charge separation in DANS-(TAIPDI)(n) and ANADS-(TAIPDI)(n) occurs within 1.5 and 1.6 ns, respectively, calculated from the quenching of singlet excited states. The lifetimes of charge-separated states are determined to be 44 and 96 mu s, at least 10(5) times slower than that of BSSBP-(TAIPDI)(n) due to remarkably improved electron transport throughout the (TAIPDI)(n).