Inclusion of cavitands and calix[4]arenes into a metallobridged para-(1H-imidazo[4,5-f][3,8]phenanthrolin-2-yl)-expanded calix[4]arene

A highly preorganized, deep metallocavitand of nanoscale dimensions containing rhenium atoms at the four corners can be readily synthesized from a simple formyl-substituted calix[4]arene and 3,8-phenanthroquinone. Unsubstituted calix[4]arenes and cavitands without substituents on the lower rim are the ideal guests for such an expanded calixarene (see picture), and are included with binding constants of 103-105 M^-1.

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