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In supramolecular chemistry [1] synthetically designed organic constituents interact noncovalently, in a directed and specific way to form host-guest complexes of higher complexity. The ability to tailor the molecular interplay with respect of chemical design, specificity, and molecular switching opens up the development of new molecular materials for artificial molecular recognition, molecular organization, and selfassembly. We have used mechanical single-molecule force spectroscopy to investigate the binding of individual resorc-[4]arene-ligand host-guest complexes. By using diluted samples of the host and guest molecules that are modified with a long linker which is attached to an atomic force microscope (AFM) tip, we were able to prevent multiple binding and to observe single host-guest unbinding events in a supramolecular system for the first time. The molecular binding forces, their dependence on external loading rates, the rate of dissociation, and the molecular cavity length directly relate to the molecular properties of the supramolecular species and are consistent with an activated decay of a metastable bound state, a finding already established for biological receptor-ligand complexes. This result allows new insights into the mechanisms, kinetics, and thermodynamics of intermolecular association in chemistry and biology, and opens new possibilities in the investigation, design, and development of synthetic receptor systems.Calixarenes are model receptor systems providing synthetic receptor cavities for the inclusion of small cationic guests, such as alkali-metal or ammonium ions. [2][3][4][5] Organic cations, such as ammonium ions, play a significant role in molecular recognition processes in nature (e.g. in protein side chains). Calix[n]arenes, generally, are a class of macrocyclic compounds formed by the base-catalyzed condensation of nphenol derivatives and formaldehyde. [2,3] The resorc [4]arenes [6,7] considered herein are calixarenes formed from four

2-[(2E)-3-(4-tert-butylphenyl)-2-methylprop-2-enylidene]malononitrile (DCTB, dicyano..tert-butyl ...) has proven to be an excellent nonprotic matrix for very labile compounds, especially for substituted fullerenes. This is mainly due to its extremely low onset of ion production. This matrix works mainly as an electron transfer agent, i.e. the ions produced are radical anions or cations, respectively. It works equally well to transfer evaporation energy to charged oligomers and with proton labile compounds (not shown here).

We report herein the observation of a hexameric structure of a hydroxyresorc[4]arene in the solid state, enclosing a large interior space. This artificial molecular container is stabilized only by hydrogen bonds. The tendency to form aggregates in solution is demonstrated mainly by means of ESI‐MS methods.

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Three photochemical reactions were investigated under solar irradiation conditions with moderately concentrated sunlight: the photoacylation of naphthoquinone with butyraldehyde and the dye-sensitized photooxygenations of citronellol and 1,5-dihydroxynaphthalene, respectively. All reactions were easily performed on multigram-to-kilogram scales using cheap and commercially available starting materials, and yielded important key intermediates for industrial applications.

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