Understanding and control of weak intermolecular interactions,
including π-interactions, is an element toward the strategic
design of supramolecular materials. In this work, we describe an approach
to promoting cofacial π-stacking in the solid state by preparing
polycyclic aromatic compounds that bear complementary electron-rich
and electron-poor rings. Specifically, we describe the synthesis and
single crystal structures of a series of six dissymmetric systems
(three dibenzo-p-dioxins and three phenoxazines)
comprised of one electron-rich and one electron-deficient ring. In
all cases, anti-co-facial π–π
interactions were observed, but no significant C–H···π
interactions. These observations were compared with similar structures
in the Cambridge Structural Database, and it was found that the presence
of bulky substituents, lattice solvent, and stronger intermolecular
interactions interfere with efficient π-stacking. Both qualitative
and quantitative evaluations of the newly reported structures, and
database examples, are included.