Crystal engineering using co-crystallisation of phenazine with dicarboxylic acids
Co-crystallisation of phenazine 1 with six dicarboxylic acids was carried out in order to test the robustness of a "strong/weak" coupling, IV, in the design of supramolecular assemblies. Complexes of 1 with the trans-olefinic acids fumaric 2a and mesaconic 2b comprised 1∶1 (base∶acid) stoichiometric tapes assembled solely via the strong/weak coupling. Complexes of 1 with the corresponding cis-isomeric acids maleic 3a and citraconic 3b comprised 1∶2 stoichiometric tapes in which the acid molecules were assembled to give centrosymmetric dimers. Complexes of 1 with the aliphatic dicarboxylic acids succinic 4a and glutaric 4b comprised 1∶1 and 1∶2 stoichiometric tapes respectively. In each of the co-crystal structures, tapes may be considered to form stacks in which the long axes of the tapes are parallel. In the 1∶1 complexes, tapes in adjacent stacks are twisted relative to one another with a similar arrangement of C–H⋯O interactions occurring for each structure between stacks. In the 1∶2 complexes, tapes in adjacent stacks are arranged with their long axes parallel. The exact packing arrangement varied from herringbone to a planar-sheet structure. The arrangement of C–H⋯O interactions also varied between each of the 1∶2 complexes.