Hybrid[4]arenes with anthracene units and tuneable cavities

We present the synthesis of hybrid[4]arenes via a one-pot reaction of 1,4,5,8-tetramethoxyanthracene and 1,3-dimethoxybenzene with formaldehyde catalyzed by TFA. Two new C2h-symmetric macrocycles having different substitution patterns at anthracene units were obtained. Both X-ray structure analysis and molecular modelling reveal a parallel arrangement of the anthracene units with an interplane distance of 4.8 A. A comparison of UV and fluorescence spectra of hybrid[4]arene and a monomeric anthracene unit indicates that the energies and intensities of the absorption bands (scaled to the same number of chromophores) remain similar. However, for the macrocycle the quantum yield of emission is increased, which may originate from its rigid structure. Hybrid[4]arene was post-macrocyclization modified by the Diels–Alder reaction with benzyne and a macrocycle with an expanded cavity was obtained. The expanded cavity macrocycle is able to selectively complex and solubilize pyridinium iodide in chloroform.