A supramolecular approach for potential detection of SO2 is presented, which is based on the "old" donor-acceptor chemistry between SO2 and amines and includes an indicator-displacement assay. When amines were added to Zn-tetraphenylporphyrin 1 in CHCl3, the solution changed from red to dark green. A bathochromic shift of Deltalambda approximately 10 nm was observed for the Soret band, indicating the formation of 1*amine complexes. After this, SO2 gas was introduced, and the original red color of the solution was restored. The Soret band returned to its position for free porphyrin 1. The 1*amine complexes dissociated, and new SO2*amine adducts formed. Porphyrin 1 thus served as an indirect colorimetric indicator for SO2. The system discriminates between SO2 and such typical exhaust gases as COX, NOX, and H2O. From the indicator-displacement assay, the Kassoc values between 1000 and 30 000 M-1 for SO2*amine complexes were determined, which are comparable to those obtained by direct titration experiments between SO2 and the amines. Spectroscopic features of SO2*amine complexes are also presented.

[reaction: see text] Encapsulation data for hydrophobic hydrocarbon gases within a water-soluble hemicarcerand in aqueous solution are reported. It is concluded that hydrophobic interactions serve as the primary driving force for the encapsulation, which can be used for the design of gas-separating polymers with intrinsic inner cavities.

SO2 gas is effectively used for the preparation of N,N'-diarylsulfamides and shape-persistent sulfamide polymers, which utilize a network of intermolecular N-H...O=S hydrogen bonds to self-assemble into soft porous materials.

The principles and techniques of molecular encapsulation, as applied to environmentally, biologically, and commercially important gases, are reviewed. The gases may be trapped within natural (clathrates, cyclodextrins) or synthetic (cryptophanes, carcerands, calixarenes) cavities. The physical and chemical features of the cavities are key to understanding which gases may be trapped and to what extent. These trapping materials possess a host of applications, from gas sensing and separation to acting as storage devices and microreaction vessels.

Even better than the real thing? As host molecules, long synthetic nanotubes may be reasonable alternatives to single‐walled nanotubes. For example, calixarene‐based nanotubes effectively pack into infinite tubular bundles in the solid state (see picture), and they can be easily filled with guest molecules to form stable, but reversible, encapsulation complexes.