BOQUIPHY-Fullerene C60 Dyad: An Asymmetric Boron Chromophore as a Donor Platform for Photodynamic Inactivation

An asymmetric BOQUIPHY-fullerene C60 dyad (BQP-C60) was synthesized to explore polarized di-BF2 chromophores as donor platforms for photodynamic applications. The BOQUIPHY scaffold, featuring mixed N-B-N and N-B-O chelation motifs, acts as a visible-light antenna, while C60 functions as an electron/energy acceptor and spin converter. Spectroscopic studies showed that covalent attachment promotes efficient intramolecular energy transfer from BOQUIPHY to C60. Electrochemical analysis reveals successive fullerene reductions alongside a BOQUIPHY-based oxidation, defining a donor-acceptor redox alignment that enables thermodynamically favorable photoinduced charge separation. Visible spectroelectrochemistry further supports electronic communication between donor and acceptor fragments. BQP-C60 showed higher apparent photodynamic activity under green-light irradiation, with a DMA photooxidation rate constant of 3.86 × 10-3 s-1, exceeding those of its individual counterparts. This improved apparent activity was driven by the greater absorbed-photon flux of the dyad, highlighting the antenna effect of the BOQUIPHY unit. Accordingly, BQP-C60 caused the fastest bacterial inactivation and completely suppressed recovery of Pseudomonas aeruginosa and Staphylococcus aureus in planktonic cultures. These results establish donor-acceptor engineering of asymmetric di-BF2 frameworks as a strategy for developing heavy-atom-free photosensitizers with applications in antimicrobial photodynamic therapy.