Attractive Dispersion Interactions Versus Steric Repulsion of tert-Butyl groups in the Crystal Packing of a D3h-Symmetric Tris(quinoxalinophenanthrophenazine)

The crystalline packing of a pi-extended D-3h-symmetric triptycene reveals a particular pi stacking motif with an almost-eclipsed arrangement of adjacent pi planes despite the steric repulsion of tert-butyl substituents. Four model compounds were analyzed by using single-crystal X-ray diffraction and theoretical calculations to study the influence of dispersion interactions of molecular parts and understand the relationship between the molecular structure and this unique packing motif.