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Reinvestigation of Supramolecular Complexes with Cyclophanes of the Stetter and Koga Type: Agreement and Disagreement with Solid‐State Structures
Author(s) -
Wald Peter,
Schneider HansJörg
Publication year - 2009
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.200900384
Subject(s) - chemistry , supramolecular chemistry , cyclophane , titration , benzene , stereochemistry , crystallography , solid state , aqueous solution , organic chemistry , crystal structure
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 (Δ G = 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)