A hunter hunted! 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.

The reaction of tetra-p-formyltetra-O-propylcalix[4]arene with phenanthrenequinone in the presence of NH(4)OAc affords compound 2, a new class of calixarene with an expanded aromatic cavity, that could be stabilized by hydrogen-bonded bridges and/or ion pairing, thus preventing collapse into fully stacked pinched cone conformations as depicted. Two partially protonated calixarenes interdigitate in the solid state to give rise to a self-assembled face-to-face dimer, stabilized by pi-pi stacking interactions.