We describe the one-pot synthesis, unique geometries and intriguing host–guest properties of a new class of supramolecular macrocycles – biphen[n]arenes (n = 3, 4).

The complexation of neutral 1,4-dihalobutanes with simple pillar[5]arenes was investigated. The results indicate the formation of interpenetrated complexes, where the dispersive interactions dominate the complex stability. Typically, 1,4-diiodobutane displays the strongest binding strength with ethylpillar[5]arene [K(a) = (1.0 ± 0.1) × 10(4) M(-1)], up to 120 fold as compared with 1,4-difluorobutane.

The selective and effective binding of secondary ammoniums with a weakly coordinating tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (BArF) counteranion by per-ethylated pillar[5,6]arenes is reported. The construction of a first pillararene-based self-sorting system consisting of two wheels and two axles is also described.

The complexation behavior of pillar[6]arene hosts towards a carbonium ion, tropylium tetrafluoroborate (T·BF4), and the formation of novel charge-transfer (CT) inclusion complexes are described. In contrast, smaller pillar[5]arenes and larger pillar[7]arenes cannot form such complexes due to the unsuitable cavity dimensions.