Design and construction of organic crystals: Orthogonal recognition of pioperazinediones derived from unnatural alpha-amino acids

Abstract

A paradigm and theoretical model for the design and construction of acentric crystalline solids is presented. In theory, molecular assembly in a predetermined arrangement will result for molecules that possess and participate in three chemically and geometrically orthogonal intermolecular interactions. A class of piperazinediones was designed to possess such orthogonal recognition elements and may provide an appropriate scaffold for the rational design of molecular building blocks for construction of acentric crystals. The topography and conformational rigidity of this scaffold limit packing options, which facilitate prediction of crystal structures from consideration of readily identified forces associated with three orthogonal recognition elements. Recognition elements can be introduced and modified by changing the functional groups on the scaffold via chemical synthesis. Structural variability facilitates exploration and exploitation of these molecules. A family of organic molecules that satisfy many of the conditions of the theoretical model is described and evaluated on the basis of their design, synthesis, and characterization.