Inclusion complex of calix[8]arene-C₆₀: Photophysical properties and its behaviour as singlet molecular oxygen sensitiser in the solid state

The inclusion complex calix[8]arene-C₆₀ has been studied in the solid state by means of nanosecond laser flash photolysis with diffuse reflectance (DRLFP) and NIR luminescence (TRNIR) detection techniques. The recorded transient absorption spectrum and its kinetics are similar to those showed by the inclusion complex of γ-cyclodextrin-C₆₀ in solid state. Contrarily, the new complex shows a very different behaviour against oxygen: the deduced deactivation quenching constant by molecular O₂ is k_q(O₂) = (1.1±0.1) × 10⁸ dm³ mol^-1 s^-1 in solid state, while the deactivation of triplet γ-cyclodextrin-C₆₀ by molecular O₂ in solid state had been reported as negligible. Consistent with this, TRNIR shows unequivocally that the solid calix[8] arene complex photosensitises the formation of singlet molecular oxygen. O₂(¹Δ_g), while the γ-cyclodextrin complex does not. O₂(¹Δ_g) has a lifetime of 16 μs in the heterogeneous solid calix[8] arene complex-air system. Both complexes seem to show complementary properties to be used in the area of new materials.