BUCKY(BASKET)BALL - STABILIZATION OF ELECTROGENERATED C-60(CENTER-DOT-) RADICAL MONOANION IN WATER BY MEANS OF CYCLODEXTRIN INCLUSION CHEMISTRY

A water-soluble magenta gamma-cyclodextrin inclusion complex of C-60 (gamma-CD/C-60) was prepared by a mild method which involved solubilizing C-60 in carbon disulfide followed by extracting C-60 With a gamma-CD aqueous ethanolic solution. The UV-visible spectroscopy of gamma-CD/C-60 and spectroelectrochemistry of the electrogenerated gamma-CD/C-60- radical monoanion in water resemble those of C-60 in n-hexane and C-60- in dichloromethane, respectively, indicating that the electronic properties of the C-60 and C-60- guests are practically unaffected by molecular inclusion. The FT-IR spectrum of solid gamma-CD/C-60 is only slightly different from that of gamma-CD. Cyclic voltammetry of the gamma-CD/C60 complex in aqueous 0.15 M LiClO4 solution shows three one-electron electroreductions of which only the first two, of E(1/2) values equal to -0.57 and -1.03 V vs SCE, are reversible. The ESR spectrum in a frozen 0.2 M LiClO4 aqueous solution of electrogenerated gamma-CD/C-60- is similar to that of C-60- in aprotic solvents. The ESR line shape and linewidth are dependent upon the temperature with an activation energy, E(a) = 0.043 eV, while the g value, equal to 1.998, is temperature independent over the 77-220 K range.