We prepared a rigid, simple,spiro compact electron D/A dyad showing a long-lived 3CT state(0.94 ms) based on a new electron spin-control method using SOCT-ISC, without heavy atoms or chromophores with intrinsic ISC ability.
We prepared a conceptually novel, fully rigid, spiro compact electron donor (Rodamine B, lactam form)/acceptor (naphthalimide) orthogonal dyad to attai long-lived triplet charge transfer (3CT) state, based on electron spin control and using spin-orbit charge transfer intersystem crossing (SOCT-ISC). Transient absorption (TA) spectra indicate that the first charge separation (CS) takes place within 2.5 ps. Subsequent SOCT-ISC occurs in 8 ns to produce the 3NI* state. Finally a slow secondary CS (125 ns) produces the long-lived 3CT state (0.94 ms in deaerated n-hexane) with a high energy level (ca. 2.12 eV). The cascade photophysical processes of the dyad upon photoexcitation are summarized as 1NI*-1CT-3NI*-3CT. An EEEAAA electron-spin polarization pattern was observed for the naphthalimide-localized triplet state with time-resolved electron paramagnetic resonance (TREPR) spectroscopy. The structure of our spiro compact dyad structure and the electron spin-control approach are different as compared to previous methods for which invoking transition-metal coordination or chromophores with intrinsic ISC ability is mandatory. This new method of accessing long-lived 3CT states is useful for artificial photosynthesis, photovoltaics, photocatalysis and fundamental photochemistry studies.
Published as:
Liu, D., El-Zohry, A., Taddei, M., Matt, C., Bussotti, L., Wang, Z., Zhao, J., Mohammed, F.O., Di Donato, M., Weber, S. Long Lived Charge Transfer State Induced by Spin-Orbit Charge Transfer Intersystem Crossing (SOCT-ISC) in a compact Spiro Electron Donor/Acceptor Dyad (2020) Angewandte Chemie - International Edition DOI:10.1002/anie.202003560