Organic crystal engineering with piperazine-2,5-diones. 2. Crystal packingof weakly dipolar piperazinediones derived from 2-amino-4-bromo-7-methoxyindan-2-carboxylic acid

Piperazine-2,5-diones with the potential to manifest three chemically disti nct and linearly independent intermolecular interactions were synthesized f rom the enantiomers of 2-amino-4-bromo-7-methoxyindan-2-carboxylic acid. Sa mples of enantiomerically pure, racemic, and meso piperazinediones were cha racterized in the solid state by X-ray crystallography. "Ladder-like" inter molecular amide-to-amide hydrogen bonding interactions were observed in eac h case, establishing tape structures parallel to one crystallographic axis. The observed tape morphologies and crystal packing closely resemble that p reviously observed for a topographically similar tetramethoxy-piperazinedio ne. The results obtained demonstrate that the weak dipoles associated with the p-bromoanisole moiety play no role in determining order in the crystall ine state. (C) 1999 Elsevier Science Ltd. All rights reserved.