Evidence of preferential pi-stacking: a study of intermolecular and intramolecular charge transfer complexes.

Nine combinations of pi-electron donors and acceptors were examined by UV-vis, fluorescence and (1)H-NMR spectroscopy to identify pi-stacked charge transfer complexes in macromolecular and supramolecular constructs. The high association constant of pyrene and naphthalene diimide suggests a preferentially pi-stacking pair rationalized by frontier orbital congruence.