Nonparallel chain axes in polymeric molecular crystals

The crystal structure of two semiflexible dicarboxylic acids forming chains is reported; these compounds are models for the crystal packing of polyest ers based on 1,5- or 2,7-dihydroxynaphthalene and aliphatic dicarboxilic ac ids and, more generally, for crystal packing of semiflexible chains contain ing conformationally blocked aromatic cores along the chain. In both crysta l structures, chain axes are not parallel to each other, this unusual featu re being connected, seemingly, with the lateral packing of aromatic cores p resent in the molecules.