The encapsulation of guest molecules into reversibly formed, self-assembling capsules [1] and reactions mediated or even catalyzed [2] by encapsulations mimic biological processes such as substrate recognition in enzymes and its conversion into metabolites. Besides their particular architecture, it is this feature which makes them highly interesting research objects. Pyrogallarenes and resorcinarenes such as 1-3 (Scheme 1) were shown to form hexameric capsules in the solid state [3] and in solution [4] through the formation of complex networks of hydrogen bonds. Water molecules are usually involved to complete the network for the resorcinarenes, [5] while pyrogallarenes assemble without the need for water incorporation. Guests such as solvent molecules, [6] quaternary ammonium ions, [7] and cobaltocenium [8] can be encapsulated in the large, approximately 1200 3 , cavity. Despite early attempts by Mattay and co-workers,[3b] the hexameric capsules have not been successfully characterized by mass spectrometry [9] as a consequence of three difficulties: 1) It is not always easy to provide the necessary charge without severely interfering with the assembly. This problem can easily be solved for the capsules under study here by using cationic guests encapsulated inside the cavity. 2) Nondestructive desorption of the ions of interest into the gas phase could not be achieved before the advent of electrospray ionization. 3) Finally, the stability of the assembly in the gas phase may[*] Dipl.-Chem. M. Kogej, [+] Prof.

Crystallization studies of C-methyl pyrogallarene with potassium, rubidium and caesium bromides or chlorides resulted in a hydrogen bonded molecular cage in which the alkali metal cations are eta6 coordinated to aromatic rings via strong cation-pi interactions.

In the acid-catalyzed synthesis of ethyl pyrogall[4]arene, a novel hexamer, ethyl pyrogall[6]arene, is obtained as a readily isolable minor product. Pyrogall[6]arene can be isolated from the reaction mixture in three different ways yielding the hexamer in different forms and stabilities. Crystallization from DMSO and then recrystallization from acetone gives a stable crystalline solid, recrystallization directly from acetone yields an unstable white powder, while direct recrystallization from THF gives a stable white powder. Both pyrogall[4]arene and pyrogall[6]arene crystallize readily with DMSO filling the voids in the crystal lattice. Co-crystallization studies of the hexamer isolated by recrystallization from acetone resulted in a novel directly hydrogen-bonded capsule formed by two pyrogall[4]arenes and an included TMA cation, while the DMSO/acetone isolated product yielded the intact hexamer with clathrate-type TMA inclusion.

The assembly of C-methyl resorcinarene into a tubular supramolecular solid-state structure, its thermal stability, and its hosting properties are reported. Careful control of the crystallisation conditions of C-methyl resorcinarene and 1,4-dimethyl-1,4-diazoniabicyclo[2.2.2]octane (1,4-dimethyl DABCO) dibromide leads to a formation of two crystallographically different, but structurally very similar, solid-state nanotube structures. These structures undergo a remarkable variety of supramolecular interactions, which lead to the formation of 0.5 nm diameter nonpolar tubes through the crystal lattice. The formation of these tubes is templated by suitably sized small alcohols, namely, n-propanol, 2-propanol, or n-butanol. The self-assembly involves close pi...pi interactions between the adjacent resorcinarenes, and C--H...pi and cation...pi interactions between the resorcinarenes and the guest 1,4-dimethyl DABCO dications. The crystals of these supramolecular tube structures are thermally very stable and the included solvent alcohol can be removed from the tubes without breaking the single-crystalline structure of the assembly. After removal of the solvent molecules the tubes can be filled with other small, less polar solvent molecules such as dichloromethane.

„Survival of the fittest“: Nur diejenigen hexameren Pyrogallaren‐ und Resorcinarenkapseln, die ein Gastkation der richtigen Größe, Gestalt und Symmetrie enthalten (siehe Bild), überleben die Elektrospray‐Ionisation, die ihre massenspektrometrische Detektion ermöglicht. Tandem‐MS‐Experimente mit massenselektierten Ionen belegen, dass die Hexamere ihre Kapselstruktur auch in der Gasphase beibehalten.