Synthesis and Photophysical Properties of a Supramolecular Host–Guest Assembly Constructed by Fullerenes and Tryptamine Modified Hypocrellin

The metal coordination polymer of hypocrellin A bearing tryptamine motif (M–DTrpHA) can include fullerene via a two-point interaction, involving π–π stacking and electron donor–acceptor interaction. The 1:1 host–guest system M–DTrpHA/fullerene exhibits a moderate association constant <i>K</i>_a (6.62 × 10⁴ to 6.46 × 10⁵ M^–1). Both of the metal ions in M–DTrpHA and the substituents connected to the fullerene core play important roles in stabilizing the M–DTrpHA/fullerene complex. Transient absorption spectral and NIR absorption spectral results demonstrate that, in the M–DTrpHA/fullerene system, efficient photoinduced electron transfer from the tryptamine group in M–DTrpHA to fullerene may occur, resulting in a long-lived fullerene anion radical. The observed order of quantum yield (Φ_ET^T) and rate constants (<i>K</i>_ET^T) for electron transfer via ³C₆₀* is Y³⁺–DTrpHA > La³⁺–DTrpHA > DTrpHA, consistent with their binding ability to C₆₀. The nanostructure of M–DTrpHA is rearranged to form an interpenetrating network after interaction with fullerene