Enhanced Triplet Sensitizing Ability of an Iridium Complex by Intramolecular Energy-Transfer Mechanism
Enhanced Triplet Sensitizing Ability of an Iridium Complex by Intramolecular Energy-Transfer Mechanism
复制标题
通过分子内能量转移机制增强铱配合物的三重态敏化能力
DOI：
10.1021/acs.jpca.8b04807
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发表时间：
2018
影响因子：
2.9
通讯作者：
Ma Yuguo
中科院分区：
文献类型：
--
作者：
Guo Xinyan;Chen Qi;Tong Yujie;Li Yao;Liu Yiming;Zhao Dahui;Ma Yuguo
本文研究了一种含三环化Ir（III）与芘衍生物的双发色团光敏剂的光动力学性质，包括分子内和分子间三重态能量转移（ET）。由于两个发色团的三重态能隙，在光激发时快速建立可逆的分子内三重态ET平衡，其中三重态激子主要位于光稳态中的受体侧。由于三重态芘的衰变率非常小，观察到了相当长的三重态寿命（2 ms）。接下来，分子间三重态-三重态ET性质进行了研究。利用稳态和时间分辨光谱，发现从Ir络合物和敏化剂中的芘单元到溶液中的外部三重态受体（未连接的游离芘衍生物）的ET速率常数分别约为109 s-1和108 M-1 s-1。尽管较低的ET速率常数，栓系芘作为主要的分子间ET通道，因为大，有利的分子内ET平衡（K = 103）。重要的是，这种级联ET过程，从Ir络合物到连接的芘，然后到游离芘，提供了一个整体改善的ET效率比直接ET从Ir络合物到游离芘，凭借小得多的自发衰变率相比，金属络合物。最后，更有效的ET能力的实验证明，通过应用分子作为敏化剂在三重态-三重态湮灭上转换。双色敏化剂实现了上转换发射强度比单色Ir络合物类似物高5倍。
The photodynamic properties involving both intra- and intermolecular triplet energy transfers (ET) of a bichromophoric photosensitizer having a tris-cyclometalated Ir(III) tethered with a pyrene derivative are studied. Due to the triplet energy gap of the two chromophores, a reversible intramolecular triplet ET equilibrium is quickly established upon photoexcitation, with the triplet exciton mainly residing on the acceptor side in the photostationary state. By virtue of the very small decay rate of triplet pyrene, a considerably extended triplet lifetime (2 ms) is observed. Next, the intermolecular triplet–triplet ET properties are investigated. Using steady-state and time-resolved spectroscopy, the ET rate constants from the Ir complex and pyrene unit in the sensitizer to an external triplet acceptor (unattached, free pyrene derivative) in solution are found to be around 109s–1and 108M–1s–1, respectively. In spite of a lower ET rate constant, the tethered pyrene serves as the main intermolecular ET channel because of the large, favorable intramolecular ET equilibrium (K∼ 103). Importantly, this cascade ET process, from Ir complex to linked pyrene, and then to free pyrene, offers an overall improved ET efficiency than a direct ET from Ir complex to free pyrene, by virtue of the much smaller spontaneous decay rate compared to that of the metal complex. Finally, the more efficient ET ability is demonstrated experimentally by applying the molecule as sensitizer in a triplet–triplet annihilation upconversion. The bichromophoric sensitizer achieved upconverted emission intensity 5 times higher than a monochromophoric Ir-complex analogue.