On the Nature of the Transition State Characterizing Gated Molecular Encapsulations

Abstract

Gated molecular encapsulations, with baskets of type 1, are postulated to occur by the mechanism in which solvent molecule penetrates the inner space of 1, through one of its apertures, while the residing guest simultaneously departs the cavity. In the transition state of the exchange, three pyridine-based gates are proposed to assume an open position with both incoming solvent and departing guest molecules interacting with the concave surface of the host. The More O'Ferrall-Jencks diagram and linear free energy relationships (LFERs) suggest a more advanced departure of the guest when bigger solvents partake in the displacement.

On the Transfer of Chirality, Thermodynamic Stability, and Folding Characteristics of Stereoisomeric Gated Baskets

“…Indeed, gated molecular baskets of the type 1 ( V = 226 Å 3 , Figure 1, A), with three amidopyridine gates at the rim, were designed in our laboratory to form a seam of intramolecular N–H ··· N hydrogen bonds 15. The disruption of these noncovalent contacts, characterized by an activation energy of about 10 kcal/mol,16 permits the substitution of solvent residing inside the basket's cavity by a guest molecule from bulk solution 17. Accordingly, tuning the strength of the N–H ··· N hydrogen bonds in 1 by varying the electronic and steric characteristics of the amide's R substituents (Figure 1, A) enabled us to modulate the dynamics of the gates and therefore the time of the encapsulated guests in the basket 14.…”