Synthesis of a large-cavity carbazole macrocycle for size-dependent recognition.

A large-cavity carbazole macrocycle (1) is reported through condensation of a long and rigid monomer and paraformaldehyde. 1 exhibits highly selective binding of large-sized tetra( n -propyl) ammonium cation 3 + . The complexation of 3 + by 1 is counter anion-dependent, where Cl - gives the highest association constant of 3010 ± 230 M -1 .