Synthesis, Photophysical, and Chemiexcitation Properties of Luminol-Fullerene Dyads: Toward Chemiexcitation Electron Transfer.

Fullerene-based donor-acceptor (D-A) dyads have been extensively studied for their unique electronic properties, with applications in photoinduced energy conversion devices. In these systems, dynamic quenching of the excited donor's emission occurs, via energy or electron transfer to the fullerene acceptor. However, there are no reports on fullerene dyads bearing chemiluminescent donor analogues. In this context, the synthesis of two luminol-fullerene D-A dyads, bridged with alkyl chains of different lengths, is reported herein. The electronic communication between the two moieties was thoroughly evaluated, following either the photo- or chemi-excitation of the linked units. Steady state and time-resolved absorption studies, combined with emission techniques, were employed to monitor the deactivation fate of excited species. In general, a significant quenching of the excited luminol-derived emission signals was observed, revealing detectable intramolecular interactions between the two moieties. Unlike what is usually observed in other luminol-based D-A systems, quenching of the excited species generated upon photo- and chemi-excitation of the luminol-fullerene dyads is attributed to electron rather than energy transfer. This was found to be consistent with the estimated Gibbs energy of photoinduced electron transfer and with DFT theoretical calculations.