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.