Thermodynamically Controlled Synthesis of a Chiral Tetra-cavitand Nanocapsule and Mechanism of Enantiomerization

The dynamic covalent synthesis, structure and conformational dynamics of a chiral polyimine nanocapsule la are reported. Reaction of four tetraformyl cavitands and eight H2N(CH2)(2)NH2 yields quantitatively la, which has a compact, asymmetrically folded, pseudo-C-2-symmetric structure, as determined by X-ray crystallography, and encapsulates four CHCl3 and three CH3OH guests in the solid state. In solution, la enantiomerizes by passing over a barrier of Delta G(298)double dagger = 21.5 +/- 0.7 kcal mol(-1) via a refolding process.