Outsourcing Intersystem Crossing without Heavy Atoms: Energy Transfer Dynamics in PyridoneBODIPY–C₆₀ Complexes

Abstract

The excited state dynamics in two fully characterized pyridoneBO-DIPY−fullerene complexes were investigated using time-resolved spectroscopy. Photoexcitation was initially localized on the pyridoneBODIPY chromophore. The energy was rapidly transferred to the fullerene, which subsequently underwent ISC to form a triplet state and returned the energy to the pyridoneBODIPY via triplet− triplet energy transfer. This ping-pong energy transfer mechanism resulted in efficient (>85%) overall conversion of the excited state pyridoneBODIPY constituent despite a complete lack of ISC in the pyridoneBODIPY in the absence of the fullerene partner. The small difference in attachment chemistry for the fullerene did not impact the initial singlet energy transfer. However, the N-methylpyrrolidine bridge did slow both the triplet−triplet energy transfer and the ultimate relaxation rate of the final triplet state when compared to an isoxazole-based bridge. The rates of each step were quantified, and computational predictions were used to complement the proposed mechanism and energetics. The result demonstrated efficient triplet sensitization of a strong chromophore that lacks significant spin−orbit coupling.

Heavy Atom-Free Triplet Photosensitizers: Molecular Structure Design, Photophysical Properties and Application in Photodynamic Therapy

“…1.8 ns). The triplet state lifetimes of the dyads PyridoneBDP-C60-1 and PyridoneBDP-C60-2 were Recently, Blank et al studied the singlet and triplet energy transfer kinetics in Bodipy-C60 dyads using fs-TA spectroscopy (Figure 20) [97]. Two pyridoneBodipy−fullerene dyads (compound PyridoneBDP-C60-1 with an isoxazole bridge, and compound Pyri-doneBDP-C60-2 with an N-methylpyrrolidine bridge) were investigated.…”

Novel Photocatalyst Based on Through‐Space Charge Transfer Induced Intersystem Crossing Enables Rapid and Efficient Polymerization Under Low‐Power Excitation Light

“…[15][16][17][18][19][20] But heavy atoms also suffer from unavoidable drawbacks such as high synthesis cost, high bio-toxicity, and low photostability. [20,21] Thus, recently various methods of designing heavy atom-free photosensitizers were developed, [22] including radical-enhanced ISC, [23] electron spin converter enhanced ISC, [24,25] twisted π-conjugation-induced ISC, [26,27] and spin-orbit charge transfer-induced ISC (SOCT-ISC). [28] Among these approaches, SOCT-ISC has attracted significant attention in designing heavy atom-free triplet photosensitizers, due to its simple synthesis routes, tunable ISC efficiency and long excited state lifetime.…”

Multiple Pathways in the Triplet States Population for a Naphthalenediimide‐C60 Dyad

“…[37] The ping-pong energy transfer mechanism in C 60 -chromophore dyad has also been studied, i. e. in pyridoneBodipy-C 60 dyad. In this system, the process of triplet state formation involves two energy transfer steps [35] the singlet state energy is initially transferred to the fullerene, which subsequently undergoes ISC to form a triplet state and finally returns the energy to the pyridoneBODIPY via triplet-triplet energy transfer (TTET). Furthermore, the C 60 -chromophore dyads have been successfully used in triplet-triplet annihilation photon upconversion, [32,[38][39][40][41][42][43] in photocatalysis as photo reductive catalyst for either synthetic organic reactions, [31,44] or PDT.…”