Synthesis, Structure, and Computational Studies of Soluble Conjugated Multidentate Macrocycles

Conjugated, shape-persistent macrocycles based on [3 + 3] Schiff-base condensation are of interest
for supramolecular materials. In an effort to develop new discotic liquid crystals based on these
compounds, a series of macrocycles with peripheral alkoxy groups of varying length have been
prepared. The synthesis and mechanism of formation have been probed by isolation of oligomeric
intermediates. A single-crystal X-ray diffraction study of one macrocycle revealed a nonplanar,
strongly hydrogen-bonded structure. To our surprise, even with very long substituents, the
macrocycles were not liquid crystalline. This has been rationalized by ab initio calculations that
indicate the macrocycles are undergoing rotation of the dihydroxydiiminobenzene rings that may
not allow a stable discotic liquid crystalline phase. These results provide new insight into the
formation and properties of these large macrocycles and may provide guidance to developing stable
liquid crystalline materials in the future.