Zhang Xue, Sukhanov Andrey A, Yildiz Elif Akhuseyin, Kandrashkin Yuri E, Zhao Jianzhang, Yaglioglu Halime Gul, Voronkova Violeta K
State Key Laboratory of Fine Chemicals, School of Chemical Engineering, Dalian University of Technology, E-208 West Campus, 2 Ling Gong Rd., Dalian, 116024, China.
Zavoisky Physical-Technical Institute, FRC Kazan Scientific Center of Russian Academy of Sciences, Kazan, 420029, Russia.
Chemphyschem. 2021 Jan 7;22(1):55-68. doi: 10.1002/cphc.202000861. Epub 2020 Nov 25.
A 4-amino-2,2,6,6-tetramethyl-1-piperidinyloxyl (TEMPO) radical was attached to the bay position of perylene-3,4 : 9,10-bis(dicarboximide) (perylenebisimide, PBI) to study the radical-enhanced intersystem crossing (REISC) and electron spin dynamics of the photo-induced high-spin states. The dyads give strong visible light absorption (ϵ=27000 M cm at 607 nm). Attaching a TEMPO radical to the PBI unit transforms the otherwise non-radiative decay of S state (fluorescence quantum yield: Φ =2.9 %) of PBI unit to ISC (singlet oxygen quantum yield: Φ =31.8 %, Φ =1.6 %). Moreover, the REISC is more efficient as compared to the heavy atom effect-induced ISC (Φ =17.8 % for 1,8-dibromoPBI). For the dyad, ISC takes 245 ps and triplet state lifetime is 1.5 μs, much shorter than the native PBI (τ =126.6 μs). X- and Q-band time-resolved electron paramagnetic resonance spectroscopy shows that the exchange interaction in the photoexcited radical-chromophore dyad is larger than the triplet zero-field splitting (ZFS) and the difference of Zeeman energies of the radical and chromophore. The inversion of electron spin polarization from emissive to absorptive was observed and attributed to the initial completion of the quartet state population and the subsequent depopulation processes induced by the zero-field splitting.
将4-氨基-2,2,6,6-四甲基-1-哌啶氮氧自由基（TEMPO）连接到苝-3,4 : 9,10-双（二甲酰亚胺）（苝双酰亚胺，PBI）的湾区，以研究自由基增强的系间窜越（REISC）和光致高自旋态的电子自旋动力学。该二元体系在可见光区有强吸收（607 nm处的摩尔吸光系数ϵ=27000 M⁻¹ cm⁻¹）。将TEMPO自由基连接到PBI单元上，可将PBI单元原本的S态非辐射衰变（荧光量子产率：Φ =2.9 %）转变为系间窜越（单线态氧量子产率：Φ =31.8 %，Φ =1.6 %）。此外，与重原子效应诱导的系间窜越相比，REISC更高效（1,8-二溴PBI的Φ =17.8 %）。对于该二元体系，系间窜越耗时245 ps，三重态寿命为1.5 μs，远短于天然PBI（τ =126.6 μs）。X波段和Q波段时间分辨电子顺磁共振光谱表明，光激发的自由基-发色团二元体系中的交换相互作用大于三重态零场分裂（ZFS）以及自由基和发色团的塞曼能之差。观察到电子自旋极化从发射型到吸收型的反转，这归因于四重态布居的初始完成以及随后由零场分裂引起的布居减少过程。
