Supramolecular capsules are desirable containers for the study of molecular behavior in small spaces and offer applications in transport, catalysis, and material science. We report here the use of chalcogen bonding to form container assemblies that are stable in water. Cavitands 1−3 functionalized with 2,1,3-benzoselenadiazole walls were synthesized in good yield from resorcin[4]arenes. The solid-state single-crystal X-ray structure of 3 showed a dimeric assembly cemented together through multiple Se•••N chalcogen bonds. Binding of hydrophobic and amphiphilic guests in D 2 O was investigated by 1 H NMR methods and revealed host−guest assemblies of 1:1, 2:1, and 2:2 stoichiometries. Small guests such as n-hexane or cyclohexane assembled as 2:2 capsular complexes, larger guests like cyclohexane carboxylic acid or cyclodecane formed 1:1 cavitand complexes, and longer linear guests like ndodecane, cyclohexane carboxylic acid anhydride, and amides created 2:1 capsular complexes. The 2:1 complex of the capsule with cyclohexane carboxylic acid anhydride was stable over 2 weeks, showing that the seam of chalcogen bonds is "waterproof". Selective uptake of cyclohexane over benzene and methyl cyclohexane over toluene was observed in aqueous solution with the capsule. Hydrophobic forces and hydrogen-bonding attractions between guest molecules such as 3-methylbutanoic acid stabilized the assemblies in the presence of the competing effects of water. The high polarizability and modest electronegativity of Se provide a capsule lining complementary to guest C−H bonds. The 2,1,3benzoselenadiazole walls impart an unusually high magnetic anisotropy to the capsule environment, which is supported by density functional theory calculations.Article pubs.acs.org/JACS

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Host–guest complexation of α,ω-dibromides showed rabid tumbling conformation on NMR timescales and afforded mono hydroxyl bromides after hydrolysis in D2O.

We describe here the effects of metal complexation on the molecular recognition behavior of cavitands with quinoxaline walls. The nitrogen atoms of the quinoxalines are near the upper rim of the vase-like shape and treatment with Pd(II) gave 2:1 metal:cavitand derivatives. Characterization by 1H, 13C NMR spectroscopy, HR ESI-MS, and computations showed that the metals bridged adjacent quinoxaline panels and gave cavitands with C2v symmetry. Both water-soluble and organic-soluble versions were prepared and their host/guest complexes with alkanes, alcohols, acids, and diols (up to C12) were studied by 1H NMR spectroscopy. Analysis of the binding behavior indicated that the metals rigidified the walls of the receptive vase conformation and enhanced the binding of hydrophobic and even water-soluble guests, compared to related cavitands reported previously. The results demonstrated that the conformational dynamics of the cavitand were slowed by the coordination of Pd(II) and stabilized the host’s complexes.