Synthesis and Structure of Cyclic Oligo(p-phenylene oxide)s,  −(C₆H₄O)_n− (n = 6−10)

Stepwise growth of oligo(p-phenylene oxide)s and cyclization via the Ullmann coupling reaction by using CuI/N,N-dimethylglycine afforded cyclic oligo(p-phenylene oxide)s, (n = 6−10). The structure of the new cyclophanes was determined by X-ray crystallography, which revealed that they have planar or slightly bent structures with diameters of 1.0−1.5 nm.