Polymers & Functional Materials Division, CSIR-Indian Institute of Chemical Technology, Habsiguda, Hyderabad-500007, Telangana, India.
Phys Chem Chem Phys. 2018 Nov 7;20(43):27418-27428. doi: 10.1039/c8cp05509b.
A series of carbazole (CBZ)-boron dipyrromethene (BODIPY) based donor-acceptor dyads, CB1, CB2, and CB3, with CBZ as an energy donor, tethered together with spacers of varied sizes i.e., phenyl bridge, biphenyl bridge and diphenylethyne bridge, respectively, are reported. The newly synthesized dyads were characterized by various spectroscopic techniques. A comparison of the absorption and electrochemical data of the dyads with their reference compounds (i.e., 9-phenyl-9H-carbazole (C0) and N,N'-difluoroboryl-1,3,7,9-tetramethyl-5-phenyldipyrrin (B0)) revealed minimal ground-state interactions between the chromophores. Selective excitation of CBZ in the dyads at 290 nm resulted in the quenching of the CBZ emission followed by the appearance of BODIPY emission, revealing efficient energy transfer from singlet excited CBZ (1CBZ*) to BODIPY. The photoinduced energy transfer phenomenon was studied in three different solvents of varying polarity. The driving forces for energy transfer (ΔGEN) for all the dyads were found to be exothermic. The rate constants for energy transfer, kENT, measured by the femtosecond transient absorption technique in toluene were found to be in the range of 0.8-2.0 × 1010 s-1, depending on the type of spacer between the CBZ and BODIPY entities, and were in close agreement with the theoretically estimated rates according to the Förster energy transfer model. In contrast, selective excitation of BODIPY in these dyads at 485 nm resulted in small quenching of the BODIPY emission, suggesting a lack of major photochemical events originating from 1BODIPY*.
一系列咔唑（CBZ）-硼二吡咯亚甲基（BODIPY）基给体-受体二联体，CB1、CB2 和 CB3，其中 CBZ 为能量供体，分别用不同大小的间隔物（即苯基桥、联苯桥和二苯乙炔桥）连接，报告了。新合成的二联体通过各种光谱技术进行了表征。对二联体及其参考化合物（即 9-苯基-9H-咔唑（C0）和 N，N'-二氟硼基-1,3,7,9-四甲基-5-苯基二吡咯（B0））的吸收和电化学数据进行比较表明，发色团之间存在最小的基态相互作用。在 290nm 处选择性激发 CBZ 导致 CBZ 发射猝灭，随后出现 BODIPY 发射，表明从单重激发 CBZ（1CBZ*）到 BODIPY 的有效能量转移。在三种不同极性的溶剂中研究了光诱导能量转移现象。所有二联体的能量转移驱动力（ΔGEN）都被发现是放热的。通过飞秒瞬态吸收技术在甲苯中测量的能量转移速率常数，kENT，范围为 0.8-2.0×1010 s-1，取决于 CBZ 和 BODIPY 实体之间的间隔物的类型，并且与根据 Förster 能量转移模型理论估计的速率非常吻合。相比之下，在这些二联体中，在 485nm 处选择性激发 BODIPY 导致 BODIPY 发射的猝灭很小，这表明不存在源自 1BODIPY*的主要光化学事件。
