Abstract/Summary

Aromatic and heterocyclic molecules which form electronically-complementary π-π stacked complexes have recently found extensive application in functional materials, molecular machines, and stimuli-responsive supramolecular polymers. Here we describe the design and synthesis of model compounds that self-assemble through complementary stacking motifs, paralleling those postulated to exist in high-molecular weight, healable, supramolecular polymer systems. Complexation studies using 1H NMR and UV-vis spectroscopy indicated formation of a complementary complex between a π-electron rich di-pyrenyl tweezer-motif and a tweezer-like, π electron deficient bis-diimide. The binding stoichiometry in solution between the chain folding diimide and the pyrenyl derivative was equimolar with respect to the two binding motifs and the resulting association constant was measured at Ka = 1200 ± 90 M-1. Single crystal X-ray analysis of this "tweezer-tweezer" complex showed a low-energy conformation of the triethylenedioxy linker within the bis-diimide chain-fold. Interplanar separations of 3.4 – 3.5 Å were found within the π-stacks, and supporting hydrogen bonds between pyrenyl amide NH groups and diimide carbonyl oxygens were identified.