Benzo[1,3]oxathiol‐2‐one Motif‐Based a New Chromogenic Copillar[5]arene: Synthesis, Solid‐State Assembly, Photophysical Studies, and Colorimetric Recognition of S²⁻

Herein, for the first time, we have reported a route to the introduction of benzo[1,3]oxathiol-2-one group onto pillar[5]arene to synthesize a new copillar[5]arene, which gives a new pillar[5]arene derivative 1 upon further functionalization. The well-defined cavity of this new copillar[5]arene exhibits solvent inclusion properties as characterized by single-crystal X-ray structures. The present study explores the inclusion of ethyl acetate (EtOAc) and acetonitrile (CH₃CN) and the supramolecular assemblies with different features in the solid state. Copillar[5]arene 1 shows inclination to form dimers in both EtOAc and CH₃CN. While ethyl acetate-occupied macrocycles give 2D arrangement involving π-π interaction, acetonitrile-occupied macrocycles follow π-π, C-H⋅⋅⋅π, and H-bond interactions in 2D arrangement and create a rhombus-shaped molecular channel with a diameter of ~5.5 Å in 3D packing. Compound 1 shows good photophysical behavior and aggregation. It acts as a chromogenic sensor for the selective recognition of sulfide (S^2-) over a series of other anions in both organic and aqueous-organic solvents. The detection limit for S^2- is determined to be 3.81×10^-7 M.