Directing the assembly of molecular crystals

Crystalline materials made from molecular components can possess useful properties that can be tailored through judicious selection of their molecular building blocks. The utility of these materials, however, depends on molecular packing in the crystal lattice as well as the properties of the individual molecules themselves. Consequently, further advances hinge on our ability to manipulate solid-state structure in a rational and systematic manner. Although computational prediction of crystal structure remains elusive, empirical guidelines for assembling molecules into preordained crystal architectures are emerging rapidly. This article briefly describes the current state of the field, emphasizing the design of crystalline materials with structures reinforced by a two-dimensional hydrogen-bonded network, which serves as a platform for the synthesis of a diverse collection of compounds. These include host frameworks with cavities supported by organic "pillars" that can be interchanged to manipulate the size, shape, and character of the Inclusion cavities as well as the overall lattice architecture and metrics. This research has revealed some principles for crystal design that may prove useful in general while enabling exploration of the utility of these compounds.