C₆₀ fullerene-based materials as singlet oxygen O₂(¹Δ_g) photosensitizers: A time-resolved near-IR luminescence and optoacoustic study

The triplet properties of a series of fullerene dihydroderivatives of the o-quinodimethane type and of three representative inclusion complexes with γ-cyclodextrin and calix[8]arenes have been studied. It is found that chemical modification results in a decrease of the singlet oxygen quantum yield relative to with an C₆₀, average Φ_Δ = 0.76. On the other hand, encapsulation in either γ-cyclodextrin or calix[8]arene produces greatly varying results depending on host and solvent. Thus, in D₂ O the γ-cyclodextrin complex of C₆₀ sensitizes O₂(¹Δ_g) with Φ_Δ = 0.77, while the calixarene complex is totally ineffective, probably due to the occurrence of a fast charge transfer-mediated deactivation process. In CCl₄ the calixarene complex acts very much like C₆₀, i.e., Φ_Δ = 0.84.