Tris(spiroborate)‐Type Anionic Nanocycles

Full circle: New cyclic tris(spiroborate)s were prepared as molecular recognition modules for nanometer-sized cationic guests. These cyclophanes were simply prepared by treating corresponding bis(2,3-dihydroxynaphthalene)s with an equimolar amount of boric acid. The molecular recognition ability of these cyclic spiroborates was estimated in solution and crystal phases by the use of [Ir(tpy(2))](3+) as a typical example of a cationic guest.