Organic crystal engineering with piperazine-2,5-diones. 1. Crystal packing of piperazinediones derived from substituted 2-aminoindan-2- carboxylic acids

We have postulated that molecules engineered to participate in three chemically distinct and linearly independent intermolecular interactions will self-assemble in a predictable fashion. Six prototypes for molecules capable of manifesting such interactions were synthesized from 2-aminoindan-2- carboxylic acid, 2-amino-5,6-dimethylindan-2-carboxylic acid, and 2-amino- 4,7-dimethoxyindan-2-carboxylic acid. These piperazinediones were characterized in solution by NMR spectroscopy and in the solid state by X-ray crystallography. 'Ladder-like' intermolecular amide-to-amide hydrogen bonding interactions were observed in each case, establishing tape structures parallel to one crystallographic axis. Tape morphology varied depending on the arene substitution pattern and was governed by the development of arene and/or van der Waals contact interactions.