Molecular crystals with dimensionally controlled hydrogen-bonded nanostructures

Molecular crystals constructed by hydrogen bonding can be viewed as having nanostructural elements consisting of ordered, supramolecular hydrogen-bonded networks. These networks, whose dimensionalities and motifs are governed by the molecular structure and hydrogen-bonding topology of their constituents, can serve as "modules" in the design and synthesis of molecular materials. Robust supramolecular modules can reduce significantly the number of possible solid-state packing motifs, a key goal of crystal engineering strategies which aim to design and synthesize molecular solids with controlled solid-state structure and properties. Several examples of hydrogen bonded modules in molecular crystals are described, including one-dimensional hydrogen-bonded wires, two-dimensional hydrogen-bonded layers, and nanoporous hydrogen-bonded lattices with voids having differing dimensionalities. The presence of reliable modules in these materials provides for a better general understanding of the organization principles governing molecular and solid-state assembly by reducing the number of variables in systematic studies.