Further crystallographic evidence of NH center dot center dot center dot pi(system) and CO center dot center dot center dot pi(system) interactions: The structures of bis(diarylhydrazonecarbonyl)methylene derivatives [{ArPhC=NNH-C(O)}2CH2] (Ar = Ph, 2-C5H4N, 2-C4H3S)

In this study are reported the syntheses of three bis(diarylhydrazonecarbonyl)methylene derivatives [{ArPhC=NNH-C(O)}2CH2] [Ar = 2-C5H4N (5), C6H5 (6), and 2-C4H3S (7)], obtained by condensation of corresponding hydrazones with carbon suboxide, C3O2. The solid-state self-assembly of these carbonyl derivatives, giving rise to polymeric and dimeric networks, is described. In the formation of these structural features, in addition to N-H...O=C intermolecular hydrogen bonds, stabilizing intramolecular NH...pi (systems) and intermolecular CO...p (systems) interactions also seem to play an important role. Solution 1H-nmr data of compounds 5–7 indicate that the polymeric and dimeric structures are not maintained in solution and show the occurrence of keto-enolic equilibria.