A supramolecular host with a cavitand core and four cholate side arms

Abstract

Copper(I)-catalyzed azide–alkyne cycloaddition (CuAAC) was employed to synthesize a new cavitand (1) having four cholate groups covalently connected to the cavitand core. CuAAC between a tetrapropargyl cavitand 2 and 3α-azido-cholic acid 3 led to the isolation of pure cavitand 1, which was fully characterized by the usual complement of spectroscopic techniques. While its solubility was limited in pure aqueous media, the complexation of three 4,4′-bipyridinum (viologen) guests could be investigated, using square wave voltammetric (SWV) techniques, in a mixture of H₂O/DMSO (5 : 2 v/v) also containing 40 mM sodium tetraborate as the supporting electrolyte and further experimental evidence supporting the formation of a complex between cavitand 1 and V²⁺ (viologen) with a 1 : 1 stoichiometry was obtained using ITC and electrospray ionization mass spectrometry (ESI-MS). Computational studies at the GFN2-xTB/ALPB(water) semiempirical level of theory revealed that the cavitand adopts a compact globular structure in solution, while docking effectively with methylviologen as a guest without forming an inclusion complex.