Cubane Arrives on the Cucurbituril Scene

Cubane, an intriguing chemical curiosity first studied in the early 1960s, has become a valuable structural motif and has recently been involved in the structures of a great number of prospective compounds. The first dicationic supramolecular guest 5 is prepared and derived from a 1,4-disubstituted cubane moiety, and its binding behavior toward cucurbit[n]urils (CBn) and cyclodextrins (CD) is studied. The bisimidazolium salt 5 forms 1:1 inclusion complexes with CB7, CB8, and beta-CD with the respective association constants (6.7 +/- 0.5) X 10(11) M-1, (1.5 +/- 0.2) X 109 M-1, and <10(2) M-1 in water. The solid-state structures of the 5@CB7 and 5@CB8 complexes are also reported.