摘要:
Piperazine-2,5-diones with the potential to manifest three chemically distinct and linearly independent intermolecular interactions were synthesized from the enantiomers of 2-amino-4-bromo-7-methoxyindan-2-carboxylic acid. Samples of enantiomerically pure, racemic, and meso piperazinediones were characterized 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. The observed tape morphologies and crystal packing closely resemble that previously observed for a topographically similar tetramethoxy-piperazinedione. The results obtained demonstrate that the weak dipoles associated with the p-bromoanisole moiety play no role in determining order in the crystalline state. (C) 1999 Elsevier Science Ltd. All rights reserved.