Synthesis and solvent dependence of the photophysical properties of [60]fullerene–sugar conjugates Roger F. Enes, a Augusto C. Tome ´, a, * Jose ´ A. S. Cavaleiro, a Ali El-Agamey b,† and David J. McGarvey b, * a Department of Chemistry, University of Aveiro, 3810-193 Aveiro, Portugal b Lennard-Jones Laboratories, School of Chemistry and Physics, Keele University, Keele, Staffordshire, ST5 5BG, UK Received 6 May 2005; revised 18 July 2005; accepted 19 September 2005 Available online 18 October 2005 Abstract—A method for the synthesis of optically pure C 60 derivatives containing one or two D-galactose or D-glucose units is described. It involves the synthesis of sugar–malonate derivatives followed by a cyclopropanation reaction with C 60 . The solvent dependence of the photophysical properties of the methano[60]fullerene–sugar derivatives was studied using nanosecond laser flash photolysis coupled with kinetic UV–vis absorption spectroscopy and time-resolved singlet oxygen luminescence measurements. The triplet properties of these fullerenes, including transient absorption spectra, molar absorption coefficients and quantum yield for the photosensitised production of 1 O 2 were determined in toluene, benzonitrile and acetonitrile solutions. The transient absorption spectral profiles are solvent independent although small differences are observed in the transient absorption maximum: 720G5 nm for toluene, 710G5 nm for benzonitrile and 700G5 nm for acetonitrile. Triplet state molar absorption coefficients (3 T ) of C 60 derivatives vary from 9456G2090 M K1 cm K1 , for compound 10 in toluene, and 15,272G4462 M K1 cm K1 , for compound 6 in acetonitrile. Triplet state lifetimes (t T ) for methano[60]fullerene–sugar derivatives, under our experimental conditions, are similar in toluene or benzonitrile solutions (47.5G1.1 ms%t T %51.4G2.0 ms) but are lower in acetonitrile solutions (31.8G0.6 ms%t T %43.0G1.1 ms). Toluene and benzonitrile solutions of C 60 derivatives have F D close to unity. q 2005 Elsevier Ltd. All rights reserved. 1. Introduction Since their discovery, fullerenes and their organic deriva- tives have attracted great attention, mainly due to their potential utility in medicinal chemistry and materials science. 1–7 A very important property of fullerenes is their high capacity to generate singlet oxygen upon photo- irradiation, even in aqueous media. 8 Several photodynamic studies with fullerenes indicated their potential importance in medicine. 9,10 The synthesis of fullerene derivatives soluble in aqueous systems has been a prerequisite condition for attaining their efficiency in biological systems. To overcome the problem of the low solubility of C 60 , chemists have functionalised C 60 with hydrophilic groups. 11–14 However, this functionalisation can lead to fullerene aggregation. Photophysical studies can provide useful information in relation to dimerisation or aggregation of molecules. 15 In particular, the decrease of singlet oxygen and/or triplet quantum yields has been linked to aggregation in the case of aromatic hydrocarbons, 16 porphyrins 17,18 and fullerenes. 17–19 Attachment of a sugar moiety to C 60 may improve its water solubility and, since the carbohydrates play an important role in cellular recognition, cellular transport and adhesion phenomena, 20,21 compounds with higher selectivity and activity may be obtained in that way. Several C 60 -sugar conjugates have been prepared by different approaches, namely by reacting C 60 with glycosyl- idene carbenes, 22 glycosyl azides 23–25 or glycosyl azo- methine ylides 26 or by alkylation of a C 60 -pentathiolate with 2-bromoethyl glycosides. 27 Studies on the sugar-dependent phototoxicity of C 60 -sugar derivatives were reported recently. 25 Following our studies on the synthesis of potential biologically active C 60 derivatives, 28,29 we report here a simple method for the synthesis of C 60 glycoconjugates. The new compounds, containing one or two units of a monosaccharide, were prepared from commercially avail- able D-galactose and D-glucose derivatives via 0040–4020/$ - see front matter q 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.tet.2005.09.078 Tetrahedron 61 (2005) 11873–11881 Keywords: Fullerenes; Sugars; Malonates; Cyclopropanation; Singlet oxygen; Laser flash photolysis. * Corresponding authors. Tel.: C351 234 370 712; fax: C351 234 370 084 (A.C.T.); e-mail addresses: actome@dq.ua.pt; d.j.mcgarvey@chem.keele.ac.uk † Permanent address: Chemistry Department, Faculty of Science, New Damietta, Damietta, Egypt.