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.
National Engineering Research Center for Nanomedicine, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, 430074, P. R. China.
Chemistry. 2018 Dec 12;24(70):18663-18675. doi: 10.1002/chem.201804212. Epub 2018 Dec 4.
A compact naphthalenediimide (NDI)-2,2,6,6-tetramethylpiperidinyloxy (TEMPO) dyad has been prepared with the aim of studying radical-enhanced intersystem crossing (EISC) and the formation of high spin states as well as electron spin polarization (ESP) dynamics. Compared with the previously reported radical-chromophore dyads, the present system shows a very high triplet state quantum yield (Φ =74 %), a long-lived triplet state (τ =8.7 μs), fast EISC (1/k =338 ps), and absorption in the red spectral region. Time-resolved electron paramagnetic resonance (TREPR) spectroscopy showed that, upon photoexcitation in fluid solution at room temperature, the D state of the TEMPO moiety produces strong emissive (E) polarization owing to the quenching of the excited singlet state of NDI by the radical moiety (electron exchange J>0). The emissive polarization then inverts into absorptive (A) polarization within about 3 μs, and then relaxes to a thermal equilibrium while quenching the triplet state of NDI. The formation and decay of the quartet state were also observed. The dyad was used as a three-spin triplet photosensitizer for triplet-triplet annihilation upconversion (quantum yield Φ =2.6 %). Remarkably, when encapsulated into liposomes, the red-light-absorbing dyad-liposomes show good biocompatibility and excellent photodynamic therapy efficiency (phototoxicity EC =3.22 μm), and therefore is a promising candidate for future less toxic and multifunctional photodynamic therapeutic reagents.
已制备了一种紧凑型萘二酰亚胺（NDI）-2,2,6,6-四甲基哌啶氧基（TEMPO）偶联物，目的是研究自由基增强的系间窜越（EISC）以及高自旋态的形成和电子自旋极化（ESP）动力学。与以前报道的自由基-发色团偶联物相比，本体系显示出非常高的三重态量子产率（Φ=74％）、长寿命三重态（τ=8.7μs）、快速 EISC（1/k=338 ps）和在红光区的吸收。时间分辨电子顺磁共振（TREPR）光谱表明，在室温下的流体溶液中光激发时，TEMPO 部分的 D 态由于自由基部分（电子交换 J>0）猝灭 NDI 的激发单重态而产生强发射（E）极化。发射极化在大约 3μs 内反转成吸收（A）极化，然后在猝灭 NDI 的三重态的同时弛豫到热平衡。还观察到了四重态的形成和衰减。该偶联物被用作三重态光敏剂，用于三重态-三重态湮灭上转换（量子产率 Φ=2.6％）。值得注意的是，当封装在脂质体中时，红光吸收的偶联物-脂质体具有良好的生物相容性和优异的光动力治疗效率（光毒性 EC=3.22μm），因此是未来毒性更低和多功能光动力治疗试剂的有前途的候选物。
