A water-soluble complex of c60 is formed on refluxing a solution of y-cyclodextrin with solid c60; the lifetime of the triplet excited state of c60 in the complex is 83 ps in an oxygen free solution.

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Fullerene-60 can be made water-solu ble by forming an inclusion complex with y-cyclodextrin (y-CD). The complex between C , and y-CD is selectively formed; neither por R-CD, nor C, , takes part in complex formation. The UV-VIS and 13C NMR spectra of C , , in the complex are almost identical to those of C, , in organic solvents. The 'H NMR spectrum of the host, y-CD, in the complex has been identified. Only small differences to the spectrum of the free host are observed; this is interpreted as being due mainly t o a conformational change to a more conical structure in the host. Both 2 : l and 1 : 1 complexes between y-CD and C , are believed to exist in water. On heating in water, the complexes are transformed into water-soluble aggregates containing several fullerenes and y-CD molecules. On addition of excess y-CD to this solution and further heating, the initial complexes, monomeric in C , , , are reformed.The chemical properties of a compound depend on its level of aggregation which can be modified by a solvent or by hostguest complexation. Beautiful examples of the latter have been reported by Cram and others.' The new class of carbon modification, the fullerenes,2 should be no exception to this general observation. Fullerene-60 can be used as an example. It is relatively soluble in hydrocarbon solvents but not so in water.3 We have reported on a method to make c 6 0 watersoluble, that is by formation of a host-guest complex with ycyclodextrin (y-CD) in boiling water.4 Another more recent example has been reported by Verhoeven and co-workers.' They used a calixC8)arene with sulfonic acid side chains to dissolve c 6 0 in water.Paper 3/04770I

1992 other polycyclic compounds other polycyclic compounds Q 1150 39 -166 C60 Embedded in γ-Cyclodextrin: a Water-Soluble Fullerene. --(ANDERSSON, T.; NILSSON, K.; SUNDAHL, M.; WESTMAN, G.; WENNERSTROEM, O.; J.

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