posted on 2022-06-28, 17:05authored bySamuel
E. Penty, Martijn A. Zwijnenburg, Georgia R. F. Orton, Patrycja Stachelek, Robert Pal, Yujie Xie, Sarah L. Griffin, Timothy A. Barendt
This work showcases
chiral complementarity in aromatic stacking
interactions as an effective tool to optimize the chiroptical and
electrochemical properties of perylene diimides (PDIs). PDIs are a
notable class of robust dye molecules and their rich photo- and electrochemistry
and potential chirality make them ideal organic building blocks for
chiral optoelectronic materials. By exploiting the new bay connectivity
of twisted PDIs, a dynamic bis-PDI macrocycle (the “Pink Box”)
is realized in which homochiral PDI–PDI π–π
stacking interactions are switched on exclusively. Using a range of
experimental and computational techniques, we uncover three important
implications of the macrocycle’s chiral complementarity for
PDI optoelectronics. First, the homochiral intramolecular π–π
interactions anchor the twisted PDI units, yielding enantiomers with
half-lives extended over 400-fold, from minutes to days (in solution)
or years (in the solid state). Second, homochiral H-type aggregation
affords the macrocycle red-shifted circularly polarized luminescence
and one of the highest dissymmetry factors of any small organic molecule
in solution (glum = 10–2 at 675 nm). Finally, excellent through-space PDI–PDI π-orbital
overlap stabilizes PDI reduced states, akin to covalent functionalization
with electron-withdrawing groups.