Molecular containers in complex chemical systems

Abstract

Over the last decade molecular containers have been increasingly studied within the context of complex chemical systems. Herein we discuss selected examples from the literature concerning three aspects of this field: complex host-guest behaviour, adaptive transformations of molecular containers and reactivity modulation within them.

Highly efficient catalysis of the Kemp elimination in the cavity of a cubic coordination cage

“…Since the realisation that hollow molecular container molecules can accommodate guest molecules in their central cavities, [1][2][3] their ability to modify the reactivity of their bound guests has been of great interest. [4][5][6][7][8] Well known examples include Cram's stabilisation of highly-reactive cyclobutadiene; 4 Fujita's 'ship-in-a-bottle' synthesis of cyclic silanol oligomers; 5 Nitschke's stabilisation of P4 in a tetrahedral cage; 6 and the demonstration of unusual regioselectivity in a Diels-Alder reaction when the two reacting molecules are co-confined in a host cavity.…”

“…10 Coordination cages offer particular promise in this field because of the ease with which they can be formed by a self-assembly process from very simple component parts, using the predictable coordination geometries of metal ions to provide the three-dimensional ordering of the components which generates the necessary cavity. [1][2][3]8,11,12 In order for a container molecule to act as an efficient catalyst it needs to (i) recognise and bind the guest(s); (ii) accelerate the reaction by increasing the local concentration of reactants and/or stabilising the transition state; and (iii) expel the product to allow catalytic turnover. 8 Guest binding in cage cavities has been very well studied and is becoming a mature field, 1 to the extent that a modeling tool for quantitative prediction of guest binding has recently been reported by us.…”

Assembled molecular face-rotating polyhedra to transfer chirality from two to three dimensions

“…Most of these polyhedra are highly symmetric and achiral202122232425, and chiral molecular polyhedra with lower symmetry have attracted more and more attention because they increase the complexity of motifs and may bring more sophisticated functions262728293031. Generally, the construction of chiral molecular polyhedra follows two strategies: to use predetermined 3D chiral building blocks as the edges3032, vertices3334 or faces3536 of polyhedra to transfer 3D chirality of the components to the 3D chirality of the chiral structures, or to use achiral components to generate chiral metal-organic polyhedra373839404142 during a self-assembly process.…”

“Helix‐in‐Helix” Superstructure Formation through Encapsulation of Fullerene‐Bound Helical Peptides within a Helical Poly(methyl methacrylate) Cavity

“…Cyclic host molecules, such as modified cyclodextrins1a,1g and self‐assembled metal–organic cages1f,1h,1i,1l–1n and organic nanocapsules,1c are among the most extensively investigated host molecules. However, owing to their rigid and distinct conformational scaffold, a limited number of guest molecules of complementary size and shape can be entrapped in their cavities.…”