Syntheses, Structures, and Complexation Properties of Photoresponsive Crownophanes

A set of tethered bis‐benzophenone or ‐benzaldehyde derivatives was subjected to intramolecular McMurry reactions, thus affording hybrids with cyclophane and crown ether substructures (“crownophanes”). All macrocycles were formed in reasonable yields even at rather high concentrations. A comparative study showed that low‐valent titanium [Ti] exerts a strong template effect whereas alkali metal salts accumulating during its preparation have only little influence upon the preorganization of the substrates in a favorable podand‐like conformation. Ester linkages in the tethers turned out to be only partly compatible with the reaction conditions. Crystal structures of crownophanes 7, 8, and 12 are described. A 1H‐ and 13C‐NMR study on the complexation of Ag(+1) by 8 and 10 revealed that the endocyclic arene entities rather than the polyether chains are the major sites of interaction of the cation with its host.