Control of π–π Stacking via Crystal Engineering in Organic Conjugated Small Molecule Crystals

Because of their resolvable crystal structure, organic conjugated small molecules are intrinsically ideal for elucidating the relationship between microstructures and charge transport properties. It has been reported that the charge transport properties depend on molecular structure and molecular packing. In the solid state, π–π stacking of small molecules is significant in the charge transport process. Since π–π stacking of conjugated small molecules is influenced at different degrees by other intra- and intermolecular interactions, as a result, π–π stacking and further the charge transport properties can be controlled or tuned by crystal engineering through precise chemical modification. In this perspective, we give some typical examples illustrating the strategy of controlling π–π stacking in single crystals. Furthermore, we attempt to clarify the complex relationship between π–π stacking and other types of molecular interactions, and its influence on charge transport properties.