A General and High Yielding Fragment Coupling Synthesis of Heteroatom-Bridged Calixarenes and the Unprecedented Examples of Calixarene Cavity Fine-Tuned by Bridging Heteroatoms

A number of aza- and/or oxo-bridged calix[2]arene[2]triazines have been synthesized through
an unusually high yielding and efficient fragment coupling approach starting from cyanuric chloride and
resorcinol, 3-aminophenol, m-phenylenediamine, and N,N‘-dimethyl-m-phenylenediamine. These novel
macrocycles, which belong to the next generation of calixarenes or cyclophanes, form a unique cavity that
is resulted from two isolated benzene planes and two bis-heteroatom-conjugated triazine planes in a 1,3-alternate fashion. The nature of the bridging heteroatoms, i.e., combination of the electronic, conjugative,
and steric effects of the nitrogen and oxygen atoms, strongly regulates the cavity size, generating a set of
fine-tuned cavities in which the distance between two benzene rings at the upper rim ranges from 5.011
to 7.979 Å. The multiple intermolecular hydrogen bond interactions among N,N‘-dimethylated tetraazacalix[2]arene[2]triazines and among tetraazacalix[2]arene[2]triazines lead to the formation of infinite one-dimensional chain structure and two-dimensional zigzag layered structure, respectively, in the solid state.
The ease of preparation and further chemical manipulations, and the readily tunable cavity structures render
these aza- and/or oxo-bridged calix[2]arene[2]triazines the unique platforms in the study of supramolecular
chemistry.