Crystal structures of three N-(pyridine-2-carbon-yl)pyridine-2-carboxamides as potential ligands for supra-molecular chemistry.

The synthesis and single-crystal X-ray structures of three N-(pyridine-2-carbon-yl)pyridine-2-carboxamide imides, with or without F atoms on the 3-position of the pyridine rings are reported, namely, N-(pyridine-2-carbon-yl)pyridine-2-carboxamide, C12H9N3O2 (1), N-(3-fluoro-pyridine-2-carbon-yl)pyridine-2-carboxamide, C12H8FN3O2 (2), and 3-fluoro-N-(3-fluoro-pyridine-2-carbon-yl)pyridine-2-carboxamide, C12H7F2N3O2 (3). The above-mentioned compounds were synthesized by a mild, general procedure with an excellent yield, providing straightforward access to symmetrical and/or asymmetrical heterocyclic ureas. The crystal structures of 1 and 2 are isomorphous, showing similar packing arrangements, i.e. double layers of parallel (face-to-face) mol-ecules alternating with analogous, but perpendicularly oriented, double layers. In contrast, the crystal structure of 3, containing a fluoro- group at the 3-position of both pyridine rings, shows mol-ecular arrangements in a longitudinal, tubular manner along the c axis, with the aromatic pyridine and carbon-yl/fluorine moieties facing towards each other.