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Spin–Orbit Charge-Transfer Intersystem Crossing (ISC) in Compact Electron Donor–Acceptor Dyads: ISC Mechanism and Application as Novel and Potent Photodynamic Therapy Reagents |
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| Authors: | Dr Zhijia Wang Mikhail Ivanov Dr Yuting Gao Laura Bussotti Prof Paolo Foggi Huimin Zhang Prof Nino Russo Prof Bernhard Dick Prof Jianzhang Zhao Prof Mariangela Di Donato Dr Gloria Mazzone Prof Liang Luo Prof Matvey Fedin |
| Institution: | 1. State Key Laboratory of Fine Chemicals, School of Chemical Engineering, Dalian University of Technology, E-208 West Campus, 2 Ling Gong Rd., Dalian, 116024 P.R. China;2. International Tomography Center, SB RAS Institutskaya Str. 3A, and Novosibirsk State University, Pirogova str. 2, 630090 Novosibirsk, Russia
These authors contributed equally to this work.;3. National Engineering Research Center for Nanomedicine, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, 430074 P.R. China;4. LENS (European Laboratory for Non-Linear Spectroscopy), via N. Carrara 1, 50019 Sesto Fiorentino (FI), Italy;5. LENS (European Laboratory for Non-Linear Spectroscopy), via N. Carrara 1, 50019 Sesto Fiorentino (FI), Italy Dipartimento di Chimica, Universita di Perugia, via Elce di Sotto 8, 06123 Perugia, Italy;6. Dipartimento di Chimica e Tecnologie Chimiche, Università della Calabria, 87036 Arcavacata di, Rende, Italy;7. Lehrstuhl für Physikalische Chemie, Institut für Physikalische und Theoretische Chemie, Universität Regensburg, Universitätsstrasse 31, 93053 Regensburg, Germany;8. International Tomography Center, SB RAS Institutskaya Str. 3A, and Novosibirsk State University, Pirogova str. 2, 630090 Novosibirsk, Russia |
| Abstract: | Spin–orbit charge-transfer intersystem crossing (SOCT-ISC) is useful for the preparation of heavy atom-free triplet photosensitisers (PSs). Herein, a series of perylene-Bodipy compact electron donor/acceptor dyads showing efficient SOCT-ISC is prepared. The photophysical properties of the dyads were studied with steady-state and time-resolved spectroscopies. Efficient triplet state formation (quantum yield ΦT=60 %) was observed, with a triplet state lifetime (τT=436 μs) much longer than that accessed with the conventional heavy atom effect (τT=62 μs). The SOCT-ISC mechanism was unambiguously confirmed by direct excitation of the charge transfer (CT) absorption band by using nanosecond transient absorption spectroscopy and time-resolved electron paramagnetic resonance (TREPR) spectroscopy. The factors affecting the SOCT-ISC efficiency include the geometry, the potential energy surface of the torsion, the spin density for the atoms of the linker, solvent polarity, and the energy matching of the 1CT/3LE states. Remarkably, these heavy atom-free triplet PSs were demonstrated as a new type of efficient photodynamic therapy (PDT) reagents (phototoxicity, EC50=75 nm ), with a negligible dark toxicity (EC50=78.1 μm ) compared with the conventional heavy atom PSs (dark toxicity, EC50=6.0 μm, light toxicity, EC50=4.0 nm ). This study provides in-depth understanding of the SOCT-ISC, unveils the design principles of triplet PSs based on SOCT-ISC, and underlines their application as a new generation of potent PDT reagents. |
| Keywords: | Bodipy electron spin polarization perylenes photodynamic therapy spin–orbital charge-transfer intersystem crossing (SOCT-ISC) |