Control of Assembly of Dihydropyridyl and Pyridyl Molecules via Directed Hydrogen Bonding

The crystallization of two dihydropyridyl
molecules, 1,4-bis­(4-(3,5-dicyano-2,6-dipyridyl)­dihydropyridyl)­benzene
([C40H24N10]·2DMF, 1·2DMF; DMF = dimethylformamide) and 1,4-bis­(4-(3,5-dicyano-2,6-dipyridyl)­dihydropyridyl)­phenylbenzene
([C46H28N10]·2DMF, 3·2DMF), and their respective oxidized pyridyl analogues, 1,4-bis­(4-(3,5-dicyano-2,6-dipyridyl)­pyridyl)­benzene
([C40H20N10], 2) and
1,4-bis­(4-(3,5-dicyano-2,6-dipyridyl)­pyridyl)­phenylbenzene ([C46H24N10]·DMF, 4·DMF),
has been achieved under solvothermal conditions. The dihydropyridyl
molecules are converted to their pyridyl products via in situ oxidative
dehydrogenation in solution. The structures of the four molecules
have been fully characterized by single crystal and powder X-ray diffraction.
The oxidized pyridyl products, 2 and 4,
are more elongated due to aromatization of the dihydropyridyl rings
at each end of their parent molecules 1 and 3, respectively. The solid-state supramolecular structures of the
pyridyl molecules are distinct from the dihydropyridyl molecules in
terms of their hierarchical assembly via hydrogen bonding due to the
loss of primary N–H hydrogen bond donors in the two electron
oxidized tectons. Overall, the geometrically shorter molecules 1 and 3 display close-packed structures, whereas
the more extended 2 and 4 assemble into
more open supramolecular systems.