2-Cyano-N-(2,6-dimethoxypyrimidin-4-yl)-3-[4-(dimethylamino)phenyl]acrylamide and dimethylammonium 6-cyano-1,3-dimethyl-2,4,5-trioxo-1,2,3,4,5,8-hexahydropyrido[2,3-d]pyrimidin-8-ide: a pi-stacked dimer and a hydrogen-bonded ribbon containing three types of ring

The bond distances in 2-cyano-N-(2,6-dimethoxypyrimidin-4-yl)-3-[4-(dimethylamino)phenyl]acrylamide, C18H19N5O3, (I), and in the anionic component of the salt dimethylammonium 6-cyano-1,3-dimethyl-2,4,5-trioxo-1,2,3,4,5,8-hexahydropyrido[2,3-d]pyrimidin-8-ide, C2H8N2+center dot C10H7N4O3-, (II), provide evidence for the occurrence of electronic polarization. There are no hydrogen bonds in the structure of (I), instead pairs of molecules are linked into centrosymmetric dimers by a single pi-pi stacking interaction. In (II), a combination of a two-centre N-H center dot center dot center dot O hydrogen bond, a three-centre N-H center dot center dot center dot(O)(2) hydrogen bond, together utilizing all three O atoms, and a two-centre C-H center dot center dot center dot N hydrogen bond, link the components into a ribbon containing R-1(2)(6), R-2(2)(10) and R-6(6)(30) rings.