Hydrogen-bonded networks in trans-3-(3-pyridyl)acrylic acid and rctt-3,3'-(3,4-dicarboxycyclobutane-1,2-diyl)dipyridinium dichloride.

The structure of trans-3-(3-pyridyl)acrylic acid, C(8)H(7)NO(2), (I), possesses a two-dimensional hydrogen-bonded array of supramolecular ribbons assembled via heterodimeric synthons between the pyridine and carboxyl groups. This compound is photoreactive in the solid state as a result of close contacts between the double bonds of neighbouring molecules [3.821 (1) A] along the a axis. The crystal structure of the photoproduct, rctt-3,3'-(3,4-dicarboxycyclobutane-1,2-diyl)dipyridinium dichloride, C(16)H(16)N(2)O(4)(2+).2Cl(-), (II), consists of a three-dimensional hydrogen-bonded network built from crosslinking of helical chains integrated by self-assembly of dipyridinium cations and Cl(-) anions via different O-H...Cl, C-H...Cl and N(+)-H...Cl hydrogen-bond interactions.