Single-Crystal Structure Analysis of Dicarboxamides: Impact of Heteroatoms on Hydrogen Bonding of Carboxamide Groups

This research examines how heteroatoms in a six- or five-membered pyridine, thiophene or furan ring spacer between two carboxamide groups influence the hydrogen bonding for advancements in supramolecular chemistry and drug development. The solvent-free crystal structures of 3,5-pyridinedicarboxamide (PDC), 2,5-thiophenedicarboxamide (TDC) and 2,5-furandicarboxamide (FDC-subl, crystallized by sublimation), and the monohydrate structure of FDC-solv (crystallized from methanol) are described with the hydrogen-bonding analyzed by the Etter graph-set notation. The carbon atoms of the amide groups form an angle of 121 degrees in PDC, 151 degrees in TDC, 137 degrees in FDC-solv and 135 degrees in FDC-subl with the ring centroid. Only in the structure of PDC does the heteroatom act as an H-bond acceptor as part of a C11(6) chain. In TDC and FDC, the heteroatoms do not interact with the amide -NH2 groups.