Cationic cyclotriveratrylene-based glycoconjugate and its interaction with fullerene

Abstract

Fullerenes exhibit interesting biological activities both in vitro and in vivo. However, the low solubility of fullerenes in aqueous media appears to be a major problem for their biological application. To exploit water-soluble macrocyclic host systems to improve the water-solubility of fullerene, a cationic water-soluble CTV derivative containing glucosamine hydrochloride (CTV-GH) is synthesized and well characterized. The supramolecular complexation between CTV-GH and C₆₀ was investigated in organic solvent and aqueous solution, respectively, and confirmed by fluorescence, UV-vis, and Raman spectra. The CTV derivative exhibits a distinct photoluminescence, which can be used to conveniently detect its interaction with C₆₀ through spectrofluorometric titration. CTV-GH can bind C₆₀ in toluene–DMSO solution with the association constant K_a = 4.36 × 10⁵ M⁻¹ calculated on the hypothesis of forming a supramolecular complex with 1 : 1 molar ratio at 298 K. In an aqueous solution, C₆₀ has no absorption intensity due to its insolubility. However, in the presence of CTV-GH, a new characteristic peak of C₆₀ at 342 nm in the UV-vis absorption spectrum was observed for the C₆₀–CTV-GH complex and its intensity greatly increases over 24 h, which proves that CTV-GH can bind C₆₀ in aqueous solution to form a water-soluble complex. The host–guest interaction between sugar-bearing CTV and C₆₀ in aqueous solution will boost the potential biological applications of C₆₀.