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  • Reinvestigation of Supramol...
    Wald, Peter; Schneider, Hans-Jörg

    European Journal of Organic Chemistry, July 2009, Letnik: 2009, Številka: 20
    Book Review, Journal Article

    In this paper we reinvestigate the historically oldest complexations with cyclophanes of the Stetter and Koga type (1 and 2), and new macrocycle 3, which is a hybrid of the two former. NMR titrations in aqueous solution reveal that benzene forms, as known, strong complexes with Koga‐type host 2, but also weaker ones with Stetter cyclophane 1, in contrast to earlier observations with the corresponding crystals. Tosylate forms weak complexes with 1, but stronger ones with 2 and 3. The binding free energy difference (ΔG = 7 kJ mol–1) between tosylate and benzene as guest and 2 or 3 as host agrees well with the salt bridge increment found earlier with many supramolecular complexes. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) Some of the oldest reports on complexations of cyclophanes were leading to partially conflicting results. NMR spectroscopy shows that in contrast to the crystal structure Stetter's cyclophane exhibits intracavity inclusion of benzene. A new cyclophane combines features of the well‐known Koga‐ and Stetter‐type cyclophanes.