Electrostatic Control of Macrocyclization Reactions within Nanospaces

Abstract

The intrinsic structural complexity of proteins makes it hard to identify the contributions of each noncovalent interaction behind the remarkable rate accelerations of enzymes. Coulombic forces are evidently primary, but despite developments in artificial nanoreactor design, a picture of the extent to which these can contribute has not been forthcoming. Here we report on two supramolecular capsules that possess structurally identical inner-spaces that differ in the electrostatic potential (EP) field that envelops them: one positive and one negative. This architecture means that only changes in the EP field influence the chemical properties of encapsulated species. We quantify these influences via acidity and rates of cyclization measurements for encapsulated guests, and we confirm the primary role of Coulombic forces with a simple mathematical model approximating the capsules as Born spheres within a continuum dielectric. These results reveal the reaction rate accelerations possible under Coulombic control and highlight important design criteria for nanoreactors.

Recognition with metallo cavitands

“…Unlike the more dynamic watersoluble cavitands reported previously, the Pd(II)-based cavitands showed binding properties for small organic molecule guests such as alkanes, alkanols, alkanoic acids, cyclic alkanes, and cyclic carboxylic acids augur well for applications in smallmolecule sensing and recognition. The direct contact between the guest and metal is unlikely, but nearby charges are known to have profound effects on the stabilization of intermediates (25) and the course of reactions (26) inside containers (27). Metallo-cages have also found applications in the solid-state structural analysis of bound guests (28)(29)(30)(31).…”

Reversible switching of arylazopyrazole within a metal–organic cage

“…Confining reactive species to small volumes can greatly increase their effective molarity and consequently, promote chemical reactions. Such reaction acceleration has been demonstrated at interfaces [1–3], in self-assembled cages [4–7], on DNA chains [8], and on the surfaces of inorganic nanoparticles [9–10]. Additionally, nanosized cages can induce preorganization of the encapsulated species, thus inducing unusual regioselectivities in various chemical reactions [11–13].…”

Aromaticity and Chemical Bonding of Chalcogen‐Bonded Capsules Featuring Enhanced Magnetic Anisotropy

“…Preliminary calculations suggested an enhanced aromaticity near the Se atoms. Because reactions inside related containers have been shown to respond to peripheral charac-teristics such as charge [3][4][5] and Bronsted acidity, [6] we were curious to explore the origin and nature of the anisotropic magnetic environment of the capsule's interior. While O is usually not considered a chalcogen bond acceptor, it is of interest to examine this possibility in the assembly of the capsules.…”