American Chemical Society
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Comparative Structural Studies on Homologues of Amides and Reverse Amides: Unprecedented 4-fold Interpenetrated Quartz Network, New β-Sheet, and Two-Dimensional Layers

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posted on 2007-12-05, 00:00 authored by Lalit Rajput, Subhankar Singha, Kumar Biradha
The homologous series of N,N′-bis(phenyl)alkanediamides, N,N′-bis(3-pyridyl)alkanediamides, and N,N′-bis(4-pyridyl)alkanediamides (reverse amides) have been synthesized and crystallized. The crystal structures of these amides were determined and analyzed in terms of hydrogen bonding patterns. Their structural patterns have been compared with those of bis(phenylcarboxamido)alkane, bis(4-pyridinecarboxamido)alkane, and bis(3-pyridinecarboxamido)alkane derivatives (amides). The similarities in supramolecular geometries between the reverse amides and amides were studied and discussed in detail. The interference of pyridyl groups in amide-to-amide hydrogen bonds was found to be more prominent in reverse amides than amides. Conventional β-sheet patterns were not observed in reverse amides containing pyridine groups. The supramolecular patterns in reverse amides are totally deviated from those of amides when they contain 4-pyridyl groups. In this study, we found that the reverse amides form two new β-sheet patterns: one formed via N−H···N and N−H···O hydrogen bonds, whereas the other is formed by the joining of amides via water molecules (N−H···Ow and Ow−H···O). Further, one of these reverse amides found to form a 4-fold interpenetrated network with quartz topology via N−H···N hydrogen bonds.