- Lin, N.-T.; Vargas Jentzsch, A.; Guénée, L.; Neudörfl, J.-M.; Aziz, S.; Berkessel, A.; Orentas, E.; Sakai, N.; Matile, S. “Enantioselective Self-Sorting on Planar, π-Acidic Surfaces of Anion-π Transporters” Chem. Sci. 2012, 3, 1121-1127
Self-sorting at interfaces is one of the big challenges we face to prepare the functional organic materials of the future. As a first and decisive step to self-sorting into π-stacks or bundles, we here elaborate self-sorting of π-dimers in solution. Design, synthesis and study of planar naphthalenediimides (NDIs) with one shielded and one free chiral π-surface to direct self-assembly into dimers are described. Stereoisomers are isolated by chiral, preparative HPLC and characterized by X-ray crystallography. NMR studies show that racemates with almost planar, nearly identical π-surfaces prefer uniform self-sorting into homodimers at large differences in π-acidity and alternate self-sorting into heterodimers at small differences in π-acidity. In contrast, enantiomers self-sort "narcissistically" into heterodimers and diastereomers show moderate preference for homodimers. Whereas the lessons learned from dimerization are directly applicable to self-sorting of π-stacks on surfaces, anion transport in lipid bilayers is shown to require a more subtle, somewhat inverse interpretation, with diastereomeric transporters differing dramatically in activity but the least visible supramolecule being confirmed as the best performer.