Single Molecule Solvation and Its Effects on Tautomeric Equilibria in a Self-Assembled Capsule

A self-assembled cylindrical capsule provides a nanoscale environment that affects keto−enol equilibria. The equilibrium constants for encapsulated β-ketoesters show values that differ by an order of magnitude from that of the free tautomers in solution. For complexes with a single, large encapsulated guest, the inner surfaces of the capsule and the seam of the hydrogen bonds influence the equilibrium between the encapsulated keto and enol forms. For complexes of smaller β-ketoesters, the coencapsulated solvent influences the equilibria. The solvent reduces the space available and affects the positioning of the ester in the capsule