Development of Novel Molecular Functions of γ-Cyclodextrin-Bicapped C60 Supramolecular Complex and Supermacroheterocyccs with C60

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Since the first prediction of the existence of C_<60>(buckminsterfullerence) molecule with soccerball structure based on the superaromaticity concept, we have been interested in the reactivities and function of C_<60> and its derivatives. We have designed and succeeded in preparing and characterizing the water-soluble C_<60>/γ-cyclodextrin (1:2) complex (γ-cyclodextrin-bicapped C_<60>) by the inclusion of C_<60> with γ-cyclodextrin at 118 degrees Celsius for 114 h in H_20/toluene. During our study, we have found novel functions of γ-cyclodextrin-bicapped C_<60> for asymmetric reduction of ketenes and nitrogen fixation of molecular N_2 into ammonia.γ-Cyclodextrin-bicapped C_<60> mediates asymmetric reduction of prochiral alkyl aryl ketonxes using NaBH_4 as a reducing reagent to afford the corresponding chiral sec-alcohols with moderate enantioselectivity.Treatment of γ-cyclodextrin-bicapped C_<60> with an excess amount of sodium hydrosulfite under 1 atom of N_2 at 60 degrees Celsius for 1 h gives ammonia in moderate yield. We consider that the coordinated N_2 on the C_<60> molecular surface in γ-cyclodextrin-bicapped C_<60> is transformed into ammonia. Ammonia is also obtained in a lower yield with dilute H_2SO_4 under similar reaction conditions. In both cases, no formation of ammonia is observed in the absence of either N_2 or γ-cyclodextrin-bicapped C_<60>. This remarkable result may be the first example of the transformation of N_2 gas into ammonia by using only carbon, hydrogen, and oxygen elements.