Long‐Lived Triplet Excited State Accessed with Spin–Orbit Charge Transfer Intersystem Crossing in Red Light‐Absorbing Phenoxazine‐Styryl BODIPY Electron Donor/Acceptor Dyads

摘要: Orthogonal phenoxazine-styryl BODIPY compact electron donor/acceptor dyads were prepared as heavy atom-free triplet photosensitizers (PSs) with strong red light absorption (ϵ=1.33×105  M-1  cm-1 at 630 nm), whereas the previously reported based on spin-orbit charge transfer intersystem crossing (SOCT-ISC) mechanism show in a shorter wavelength range (<500 nm). More importantly, long-lived state (τT =333 μs) was observed for new dyads. In comparison, lifetime of same chromophore accessed conventional atom effect (HAE) is much =1.8 μs). Long beneficial to enhance or energy transfer, primary photophysical processes application PSs. Our approach SOCT-ISC, without invoking HAE, which may shorten lifetime. We used bisstyrylBodipy both acceptor and visible light-harvesting chromophore, shows red-light absorption. Femtosecond transient spectra indicated separation (109 ps) SOCT-ISC (charge recombination, CR; 2.3 ns) BDP-1. ISC efficiency BDP-1 determined ΦT =25 % (in toluene). The dyad BDP-3 PS triplet-triplet annihilation upconversion (upconversion quantum yield ΦUC =1.5 %; anti-Stokes shift 5900 cm-1 ).