Electronic coupling and spin-orbit charge transfer intersystem crossing (SOCT-ISC) in compact BDP-carbazole dyads with different mutual orientations of the electron donor and acceptor
Electronic coupling and spin-orbit charge transfer intersystem crossing (SOCT-ISC) in compact BDP-carbazole dyads with different mutual orientations of the electron donor and acceptor
复制标题
DOI：
10.1063/1.5145052
复制
发表时间：
2020-03-21
影响因子：
4.4
通讯作者：
Fedin, Matvey
中科院分区：
文献类型：
--
作者：
Hou, Yuqi;Kurganskii, Ivan;Fedin, Matvey
为了研究自旋-轨道电荷转移诱导的系间交叉(SOCT-ISC)，制备了BODIPY(BDP)-咔唑(Cz)致密的电子给体/受体对。观察到的电荷转移(CT)发射带显示了施主和受主之间的强电子耦合(耦合矩阵元素V-DA，0.06 eV-0.18 eV)。根据耦合强度的不同，二极体的CT状态可以是暗的，也可以是发射的。依赖温度的荧光研究证实了(LE)-L-1(局部激发)态和(CT)-C-1态之间的平衡。当Cz连接在BDP的介观位置时，可以观察到有效的ISC。有趣的是，具有非正交几何结构的并联体表现出最高的ISC效率(Phi(Delta)=58%)，这与先前的结论不同。用飞秒瞬时吸收光谱研究了光致电荷分离(CS，时间常数：0.7ps)和电荷复合(CR，约3.9 ns)。纳秒暂态吸收光谱表明，BDP定域三重态的寿命非常长(602亩S)。利用脉冲激光激发的时间分辨电子顺磁共振光谱，证实了SOCT-ISC机制，并证明了三重态的电子自旋极化高度依赖于施主和受主的相互取向。将其作为三重态光敏剂用于三重态-三重态湮没(TTA)上转换，量子产率可达6.7%。观察到了基于热重分析的二联体(tau(Df)=41.5mU S)的延迟荧光。二联体也被用作有效的光动力治疗试剂(IC50的光毒性=0.1mU M，暗毒性IC50=70.8mU M)。由AIP出版公司授权出版。
In order to study the spin-orbit charge transfer induced intersystem crossing (SOCT-ISC), Bodipy (BDP)-carbazole (Cz) compact electron donor/acceptor dyads were prepared. Charge transfer (CT) emission bands were observed for dyads showing strong electronic coupling between the donor and the acceptor (coupling matrix elements V-DA, 0.06 eV-0.18 eV). Depending on the coupling magnitude, the CT state of the dyads can be either dark or emissive. Equilibrium between the (LE)-L-1 (locally excited) state and the (CT)-C-1 state was confirmed by temperature-dependent fluorescence studies. Efficient ISC was observed for the dyads with Cz connected at the meso-position of the BDP. Interestingly, the dyad with non-orthogonal geometry shows the highest ISC efficiency (Phi(Delta) = 58%), which is different from the previous conclusion. The photo-induced charge separation (CS, time constant: 0.7 ps) and charge recombination (CR, similar to 3.9 ns) were studied by femtosecond transient absorption spectroscopy. Nanosecond transient absorption spectroscopy indicated that the BDP-localized triplet state was exceptionally long-lived (602 mu s). Using pulsed laser excited time-resolved electron paramagnetic resonance spectroscopy, the SOCT-ISC mechanism was confirmed, and we show that the electron spin polarization of the triplet state is highly dependent on the mutual orientation of the donor and acceptor. The dyads were used as triplet photosensitizers for triplet-triplet-annihilation (TTA) upconversion, and the quantum yield is up to 6.7%. TTA-based delayed fluorescence was observed for the dyads (tau(DF) = 41.5 mu s). The dyads were also used as potent photodynamic therapy reagents (light toxicity of IC50 = 0.1 mu M and dark toxicity of IC50 = 70.8 mu M). Published under license by AIP Publishing.