Orthogonal binding and displacement of different guest types using a coordination cage host with cavity-based and surface-based binding sites

Abstract

The octanuclear Co(II) cubic coordination cage system H (or HW if it bears external water-solubilising substituents) has two types of binding site for guests. These are (i) the partially-enclosed central...

Catalytic reactions in a Co12 cuboctahedral cage arising from guest encapsulation and cage-based redox activation

“…400 Å 3 ) which is ideal for accommodating a wide range of small organic guests; in its water-soluble forms, the hydrophobic effect ensures strong binding of such guests, with binding constants of up to 10 6 M −1 for optimally-sized guests; 6 a , b and the high positive charge allows the cage to accumulate anions around its surface very effectively. 6,8 This last effect is the basis for its catalytic activity as the cage uses two orthogonal 8 c interactions to bring two reaction partners into close proximity, viz. (i) an organic substrate which binds in the cage cavity via the hydrophobic effect; and (ii) accumulation of anions around the cage surface via electrostatic/ion-pairing effects.…”

Inside or outside the box? Effect of substrate location on coordination-cage based catalysis

“…1) has demonstrated a catalytic mechanism that is based on a combination of two effects. 3,6 Binding of an organic guest in the cage cavity in aqueous solution is driven predominantly by the hydrophobic effect. 3 a Additionally the high positive charge of the cage (16+) attracts counter-ions which accumulate around the cage surface, occupying in particular portals in the cage faces where they can bind strongly.…”

“…3 a Additionally the high positive charge of the cage (16+) attracts counter-ions which accumulate around the cage surface, occupying in particular portals in the cage faces where they can bind strongly. 3 a ,6 The very high local concentration of surface-bound anions surrounding the cavity-bound substrate provides co-location of two different reaction partners which can result in effective catalysis.…”

Adaptive coordination assemblies based on a flexible tetraazacyclododecane ligand for promoting carbon dioxide fixation

“…7,8 Inspired by this, many unusual metal complexes which can be used to fix CO 2 through binding with carbonate have been reported. 9–13 Coordination-directed self-assembly has been proven to be an effective approach toward the predictable construction of multicomponent artificial hosts, 14–77 where enhanced guest reactivity, 73,74,78–87 stabilization of metastable species, 88–90 and unusual reaction pathways 78,91–94 have been realized. While atmospheric CO 2 sequestration by selective binding of carbonate with coordination hosts has already been reported, 95–102 adaptive coordination hosts that contain multiple active metal sites and can reversibly encapsulate and release the carbonate are still rare.…”