Construction and photophysical properties of hypocrellin A/fullerene C70 supramolecular assembly

Interaction of hypocrellin A (HA), a naturally perylenequinonoid, with fullerene C₇₀ has been studied by UV–vis and fluorescence spectra, and the results show that HA and C₇₀ can form a supramolecular assembly HA/C₇₀ with a 2:1 stoichiometry in organic solvents and buffer solution containing poly(vinylpyrrolidone) (PVP). The triplet lifetime of HA and C70 are reduced due to the formation of supramolecular complex. Electron paramagnetic resonance (EPR) studies suggest that photoinduced electron transfer from N,N,N′N′-tetramethyldiethyleneamine (TMEDA) to the excited HA induces the generation of anion radical of HA (HA^?), followed by further electron transfer from HA^? to C₇₀. HA can mediate the electron transfer from TMEDA to C₇₀ and significantly enhance the intensity of characteristic Near-IR absorption transition of C₇₀^?, through efficient electron-transfer processes. Upon visible light irradiation, HA/C₇₀ exhibits stronger photodamage ability on calf thymus DNA under anaerobic condition than HA and C₇₀.