Conformationally adaptive thio-hemicucurbiturils exhibit promiscuous anion binding by induced fit

Unlike the double-stranded cavitands with a fixed interior, the conformational flexibility of single-stranded host molecules allows for more promiscuous host-guest complexation. This article presents a unique family of single-stranded anion receptors, thio-hemicucurbit[n]urils (thio-hCB[n]s; n = 6 and 8), which bind various anions via multiple hydrogen bonds and dispersion forces, exhibiting an induced fit and conformational adaptation. The thio-hCBs are readily accessible exclusively and quantitatively via template-driven mechanochemical synthesis from cyclic thiourea monomers. The solid-state structures of the various host-guest inclusion complexes reveal that these host molecules constitute a relatively rigid circular skeleton and eight or six rigid flaps that can easily change their tilt angle relative to the equatorial plane to maximize the guest binding interactions. These anion binders offer attractive applications ranging from water systems and environmental remediation to biomedicine of channelopathies. The new anion binders’ solvent-free, template-driven mechanochemical synthesis provides sustainable, green chemistry advantages.