Solvophobically Driven π-Stacking of Phenylene Ethynylene Macrocycles and Oligomers

Abstract

Phenylene ethynylene macrocycles and oligomers with three different side-chain linking groups (ester, benzyl ether, and phenyl ether) were synthesized to investigate their tendency to undergo solvent induced π-stacked organization. 1H NMR, UV, and fluorescence spectroscopies were used to probe two types of π-stacked supramolecular organizations: the intramolecular conformational ordering of the oligomers, and the intermolecular aggregation of the macrocycles. One important conclusion is that solvent can play a very dramatic role in modulating the strength of the interactions that drive the association of these π-stacked structures. The other important conclusion is that in a given solvent, the nature of the side chain linking group strongly influences the π-stacking propensities. It was found that macrocycles and oligomers with the ester side chain linking group were prone to adopt π-stacked structures in a range of solvents, whereas the corresponding macrocycles with benzyl ether and phenyl ether side c...