Cucurbit[7]uril⋅Guest Pair with an Attomolar Dissociation Constant

Abstract

Host⋅guest complexes between cucurbit[7] (CB[7]) or CB[8] and diamantane diammonium ion guests 3 or 6 were studied by 1H NMR spectroscopy and X‐ray crystallography. 1H NMR competition experiments revealed that CB[7]⋅6 is among the tightest monovalent non‐covalent complexes ever reported in water with Ka=7.2×1017 M−1 in pure D2O and 1.9×1015 M−1 in D2O buffered with NaO2CCD3 (50 mM). The crystal structure of CB[7]⋅6 allowed us to identify some of the structural features responsible for the ultratight binding, including the distance between the NMe3+ groups of 6 (7.78 Å), which allows it to establish 14 optimal ion‐dipole interactions with CB[7], the complementarity of the convex van der Waals surface contours of 6 with the corresponding concave surfaces of CB[7], desolvation of the CO portals within the CB[7]⋅6 complex, and the co‐linearity of the C7 axis of CB[7] with the N+⋅⋅⋅N+ line in 6. This work further blurs the lines of distinction between natural and synthetic receptors.

Synthesis of linear cucurbit[7]uril pendent copolymers through radical polymerization: Polymers with ultra‐high binding affinity

“…In addition of the oxidation method, Isaacs's group developed a different method to synthesize CB derivatives. In their works, CB [6] and CB [7] derivatives were synthesized by the condensation glycoluril hexamer with phthalaldehydes and glycoluril bis(cyclic ethers), respectively.18-20 Despite these, there is still an unmet need for new and facile methods for the construction of CB covalently linked polymers to broaden their portfolio of potential applications.The binding properties of the covalently linked macrocycle polymers are one of the key considerations in their design for specific applications. 21,22 Although their binding properties are usually determined by the binding properties of the macrocycle moieties; the structure of polymers also has a profound and sophisticated effect.…”

“…In addition of the oxidation method, Isaacs's group developed a different method to synthesize CB derivatives. In their works, CB [6] and CB [7] derivatives were synthesized by the condensation glycoluril hexamer with phthalaldehydes and glycoluril bis(cyclic ethers), respectively.…”

“…[11][12][13] The eminent binding properties of CB[6] allow these polymer nanocapsules to be decorated easily with targeting and labeling groups through host-guest interactions. Recently, allyl functionalized CB[6] and CB [7] were grafted on to hyaluronate through a thiol-ene click reaction, [14][15][16] and where employed for theranostic systems and tissue engineering applications. In addition of the oxidation method, Isaacs's group developed a different method to synthesize CB derivatives.…”

“…[1][2][3][4][5][6][7] They have been intensively researched for the past decade and have applications in a wide range of fields including molecular recognition, catalysis, drug delivery, bioassays, nanoparticle synthesis and modification, and molecular devices.1-3 Their anchoring onto macromolecules offers further opportunities to expand their applications, [8][9][10] however there are currently few examples of such reports.11-16 The relatively few reports are likely as a result of the difficulties encountered in the modification of CBs; this problem persisted until Kim's group reported the functionalization of CBs with a facile oxidation method in 2003.17 Through oxidization of CBs with persulfate, hydroxyl groups -which are suitable for further functionalization-could be introduced at their peripheries. Following that a series of polymer nanocapsules constructed with perallyloxy-CB[6] and dithiols have been reported.…”

“…[1][2][3][4][5][6][7] They have been intensively researched for the past decade and have applications in a wide range of fields including molecular recognition, catalysis, drug delivery, bioassays, nanoparticle synthesis and modification, and molecular devices.…”