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CB-carborane_ChemRxiv_final.pdf (6.16 MB)
Carborane Guests for Cucurbituril Facilitate Strong Binding and on Demand Removal
Preprints are manuscripts made publicly available before they have been submitted for formal peer review and publication. They might contain new research findings or data. Preprints can be a draft or final version of an author's research but must not have been accepted for publication at the time of submission.
High affinity guest have been reported for the macrocyclic host cucurbituril (CB), enabling widespread applications, but preventing CB materials from being returned to their guest-free state for reuse. Here we present polyhedral boron clusters (carboranes) as strongly-binding, yet easily removable, guests for CB. Aided by a Pd-catalyzed coupling of an azide anion, we prepared boron-functionalized 9-amino and 9-ammonium modified ortho-carboranes that bind to CB with a Ka=1010 M-1. Upon treatment with base, the ortho-carboranesreadily undergo deboronation to yield anionic nido-carborane, a poor guest of CB, facilitating recovery of guest-free CB. We showcase the utility of the modified ortho-carborane guest by recycling a CB-functionalized resin. With this report, we introduce stimuli-responsive decomplexation as an additional consideration in the design of high affinity host-guest complexes.