Comparative structural studies on homologues of amides and reverse amides:: Unprecedented 4-fold interpenetrated quartz network, new β-sheet, and two-dimensional layers

The homologous series of N,N'-bis(phenyl)alkanediamides, N,N'-bis(3-pyridyl)alkanediamides, and NAl-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(phenylearboxamido)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 beta-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 beta-sheet patterns: one formed via N-H center dot center dot center dot N and N-H center dot center dot center dot O hydrogen bonds, whereas the other is formed by the joining of amides via water molecules (N-H center dot center dot Ow and Ow-H center dot center dot center dot O). Further, one of these reverse amides found to form a 4-fold interpenetrated network with quartz topology via N-H center dot center dot center dot N hydrogen bonds.