A synthetic dicationic meso-bis(benzimidazolium) calix[4]pyrrole permits the sensing and chemical capture of CO 2 in its hydrated forms.

A new calix[4]pyrrole-based, dual functional, chemodosimetric sensor was developed and studied as a cyanide selective indicator; complete color bleaching was observed even in the co-presence of an excess of other anions.

Binding straps: Chiral calix[4]pyrroles 1 bearing an (R)‐ or (S)‐binol‐derived strap on one side of the tetrapyrrolic core (see picture) were synthesized and characterized. The resulting systems bind selected chiral carboxylate anions (shown in red) with high affinity in acetonitrile while at the same time exhibiting enantiomeric discrimination. PB=2‐phenylbutyrate.

A strapped calix[4]pyrrole bearing an 1,3-indanedione group at a β-pyrrolic position has been synthesized and studied as a ratiometric cyanide selective chemosensor. A concentration-dependent bleaching of the initial yellow color was observed upon addition of the cyanide anion. The bleaching, which was observed exclusively with the cyanide anion, occurred even in the presence of other anions. Spectroscopic studies provides support for a mechanistic interpretation wherein the cyanide anion forms a complex with the receptor (K = 2.78 × 104 M-1) through a fast equilibrium, which is followed by slow nucleophilic addition to the β-position of the 1,3-indanedione group. A minimum inhibitory effect from other anions was observed, a feature that could be beneficial in the selective sensing of the cyanide anion.