Theoretical investigation of the role of π–π interactions for the stability of phenylene ethynylene aggregates Original Research Article

A theoretical investigation of phenylene ethynylene macrocycles and oligomers aggregation was carried out. Two types of stacked supramolecular organization were investigated at the MP2 level: the intermolecular aggregation of macrocycles and the intramolecular conformational ordering of long oligomers. For the neutral monomer and ortho- and meta-macrocycles bound states of π–π stacked pairs were found, having binding energies of ∼−0.061, −0.378 and −0.81 eV, respectively. The relative stability between ortho- and meta-phenylene ethynylene chains and helices as function of the oligomer length n, in gas phase was also studied. The results show that π–π interactions stabilize the helical structures for long oligomers.