Multi-Component Synthesis of Tetracavitand Nanocapsules

The syntheses of three hexadecaimino nanocapsules 4b–d via the trifluoroacetic acid-catalysed condensation of four equivalents of a tetraformylcavitand 2 with eight equivalents of 1,4-phenylenediamine 3b, benzidine 3c or 4,4′-ethylenedianiline 3d, respectively, are reported. These nanocapsules are shaped like a tetragonal tetrahedron and have solvodynamic diameters of 2.5–3 nm, which were estimated from their diffusion constants. The smallest of these tetragonal tetrahedra 4b, which has a cavity volume of 1250 Å3, forms 1:1 and 2:1 complexes with R4N+Br− salts (R = n-pentyl, n-hexyl, n-heptyl) in organic solvents. Complexation-induced shifts and the slow exchange rates between the free and complexed guests are consistent with the guest being fully encapsulated inside the nanocapsule.