Journal
CHEMPHYSCHEM
Volume 21, Issue 13, Pages 1388-1401Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/cphc.202000300
Keywords
BODIPY; charge transfer; intersystem crossing; photosensitizers; triplet state
Funding
- NSFC [21673031, 21761142005, 21911530095]
- State Key Laboratory of Fine Chemicals [ZYTS201901]
- Dalian University of Technology
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Orthogonal phenoxazine-styryl BODIPY compact electron donor/acceptor dyads were prepared as heavy atom-free triplet photosensitizers (PSs) with strong red light absorption (epsilon=1.33x10(5) M-1 cm(-1) at 630 nm), whereas the previously reported triplet photosensitizers based on the spin-orbit charge transfer intersystem crossing (SOCT-ISC) mechanism show absorption in a shorter wavelength range (<500 nm). More importantly, a long-lived triplet state (tau(T)=333 mu s) was observed for the new dyads. In comparison, the triplet state lifetime of the same chromophore accessed with the conventional heavy atom effect (HAE) is much shorter (tau(T)=1.8 mu s). Long triplet state lifetime is beneficial to enhance electron or energy transfer, the primary photophysical processes in the application of triplet PSs. Our approach is based on SOCT-ISC, without invoking of the HAE, which may shorten the triplet state lifetime. We used bisstyrylBodipy both as the electron acceptor and the visible light-harvesting chromophore, which shows red-light absorption. Femtosecond transient absorption spectra indicated the charge separation (109 ps) and SOCT-ISC (charge recombination, CR; 2.3 ns) for BDP-1. ISC efficiency of BDP-1 was determined as phi(T)=25 % (in toluene). The dyad BDP-3 was used as triplet PS for triplet-triplet annihilation upconversion (upconversion quantum yield phi(UC)=1.5 %; anti-Stokes shift is 5900 cm(-1)).
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