Thumbnail image of graphical abstract

The cover picture shows not skydivers, but molecules of trimethylisocyanurate linked with CHċO hydrogen bonds in the layered hexagonal crystal structure of the 1:1 complex formed by this substance with 1,3,5-trinitrobenzene. But supramolecular patterns in crystals resemble the aerial patterns formed by skydivers in that properties of the group are distinct from those of the individual constituents. In this sense, a crystal of an organic compound is the perfect supermolecule and crystal engineering, which is the deliberate design of crystal structures of organic compounds, is the supramolecular equivalent of organic synthesis. By defining a “supramolecular synthon” as a building block that incorporates both chemical and geometrical features of sets of intermolecular interactions, the conceptual similarity between crystal engineering and classical organic synthesis is uncovered. This striking parallel is discussed by G. R. Desiraju on pp. 2328.