Modulating the Crystal Structure of Crown Ether-Appended Tetraazanaphthacenes by Formations of Metal Ion Complex and Their Radical Anion Species

Two crown ether-appended tetraazanaphthacene derivatives (15CE and 18CE) are synthesized, and their radical anion species (15CE’ and 18CE’) are further obtained by electrocrystallization. Single-crystal X-ray analysis reveals the crystal structures of all metal complexes based on 15CE and 18CE derivatives, which can be modulated by the selection of metal ion salts. 15CE and 18CE can capture metal ions depending on the size of the crown ether moieties to form metal complexes in the crystal state. On the other hand, 15CE’ and 18CE’ are generated by electrocrystallization of 15CE and 18CE using metal salts as the electrolyte, whose imino-N atoms can coordinate to metal ions. As a result, 15CE’ and 18CE’ can work as bridging radical anion ligands to self-assemble into a 3D coordination polymer and a 1D coordination polymer with helical structures, respectively. In particular, the use of both crown ether and the tetraazanaphthacene framework as a bridging radical anion ligand is the essential strategy to expand the diversity of crystal engineering because of being capable of the dramatic change in crystal structures.