In search for internal complexation in cyclodextrin-fullerene conjugates

Three new 2:1 cyclodextrin-fullerene (CD-F) conjugates have been prepared, two beta-CD-F (1b and 1c) and one gamma-CD-F (1d), of general formula C-60[C(COO-X-COOR)(2)] (1b: X = CH2, 1c, X = CH2CH2OCH2; R = NH-PMBCD (1b,c) or NH-PMGCD (1d), i.e. a beta- (1b,c) or gamma- (1d) CD, fully methylated except at one primary position, where OH is substituted by NH); they have been compared with the previously described compound la (X = (CH2)1 1, R = NH-PMBCD). The solubility in water at neutral pH of the new molecules is the highest reported to date, greater than 250 mg ml(-1). UV and NMR spectra show that aggregates are present in these water solutions. The UV spectra suggest that, at the same concentration of conjugate in water, the percentage of aggregates decreases in the order 1a > 1b similar to 1d > 1c. No evidence of internal complexation of the fullerene moiety by the CD was detected.