NMR and UV–VIS Investigation of water-soluble fullerene-60–γ-cyclodextrin complex

Abstract

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

Pseudorotaxane structure of a fullerene derivative—cyclodextrin 1 : 2 complex

“…2A), and these were distinct from those of free g-CDx and could be assigned to the C 60 Ág-CDx complex. 10 In the same manner, new peaks assigned to the 2Ág-CDx and 3Ág-CDx complexes appeared in the respective spectra ( Fig. 2B and C), which indicates that 2 and 3 are solubilised in water by inclusion in g-CDx.…”

Single and double reduction of C60 in 2:1 γ-cyclodextrin/[60]fullerene inclusion complexes by cyclodextrin radicals

“…Several systems might coexist depending on the relative concentration of cyclodextrin and C 60 , the type of preparation, the time and temperature of storage, and the presence or exclusion of air [10,[27][28][29]. In agreement with previous studies, we confirmed that mainly two forms of complexes resulted between C 60 and c-CD: (i) one featuring the C 60 included in the cavities of two c-CD, the solution having a magenta colour, typical of non-aggregated C 60 , with the ground state absorption spectrum exhibiting a small, sharp and characteristic peak at 408 nm and (ii) a second form, partially consisting of non-inclusion complexes [30], where the C 60 molecules are associated in clusters surrounded by several c-CD [10,29], the solution being yellowish-brown, a typical colour of C 60 aggregates without the 408 nm peak in the absorption ground state spectrum. In all our investigations, we exclusively used the first type of complex.…”

“…These CD are also an interesting matrix for spectroscopic studies since they are transparent throughout a part of the IR, and in the visible and near-UV spectral region. The internal diameters of the largest CD, the c-CD which are constituted by 8 glucose units, allow the formation of 2:1 c-CD/[60]fullerene inclusion complexes (c-CD/C 60 ) [10,11].…”

Biological applications of hydrophilic C60 derivatives (hC60s)− a structural perspective

“…γ-CD with a big cavity could encapsulate C60 and avoid aggregation [97]. The cell inhibition was dependent on the ability of ROS production (especially, 1 O2) and cellular uptake.…”