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 1a are reported. Reaction of four tetraformyl cavitands and eight H2N(CH2)2NH2 yields quantitatively 1a, which has a compact, asymmetrically folded, pseudo-C2-symmetric structure, as determined by X-ray crystallography, and encapsulates four CHCl3 and three CH3OH guests in the solid state. In solution, 1a enantiomerizes by passing over a barrier of ΔG298⧧ = 21.5 ± 0.7 kcal mol−1 via a refolding process.