Sun Jifu, Dai Ying, Hou Yuqi, Wu Qianwen, Ma Linzheng, Zhao Jianzhang, Wang Bo
College of Chemical and Biological Engineering, Shandong University of Science and Technology, J2-424, 579 Qianwangang Road, Qingdao 266590, P. R. China.
State Key Laboratory of Fine Chemicals, School of Chemical Engineering, Dalian University of Technology, E-208 West Campus, 2 Ling Gong Road, Dalian 116024, P. R. China.
J Phys Chem A. 2021 Mar 25;125(11):2344-2355. doi: 10.1021/acs.jpca.1c01088. Epub 2021 Mar 13.
The triplet-triplet annihilation (TTA) effect of sensitizers themselves can lead to the additional quenching of lifetimes of triplet states; therefore, how to weaken the TTA effect of sensitizers is an urgent issue to be resolved for their further applications. Besides, it remains a tremendous challenge for constructing supramolecular systems of photosensitizers based on photosensitizer-functionalized pillararenes because there have been very few investigations on them. Thus, 2,6-diiodo-1,3,5,7-tetramethyl-8-phenyl-4,4-difluoroboradiazaindacene () and ethoxy pillar[5]arene () were utilized to synthesize a -functionalized pillar[5]arene (), a cyano-containing () used as a guest molecule was also prepared, and they were used to investigate the electron-transfer mechanism between and moieties and weaken the TTA effect of moieties. The theoretical computational results of frontier molecular orbitals and isosurfaces of spin density preliminarily predicted that the cavities of the moiety had influence on the fluorescence emission of units but not on their triplet states in . The fluorescence emission intensities in a variety of solvents with different polarities and electrochemical studies revealed that there was electron transfer from to the units, and the electron-transfer process had influence on the fluorescence emission but not on the triplet states of moieties in , which verified the results of density functional theory calculations. The triplet state lifetimes of were longer than those of and and the photooxidation abilities of were better than those of and at a high concentration (1.0 × 10 M) in various solvents; in contrast, the intrinsic triplet state lifetimes and singlet oxygen quantum yields (Φ) of , , and were very similar. This was because the steric hindrance of moieties could weaken the TTA effect of moieties without influencing their intrinsic triplet state lifetimes in .
敏化剂自身的三重态-三重态湮灭（TTA）效应会导致三重态寿命的额外猝灭；因此，如何减弱敏化剂的TTA效应是其进一步应用亟待解决的问题。此外，基于敏化剂功能化柱芳烃构建光敏剂超分子体系仍然是一个巨大的挑战，因为对此的研究非常少。因此，利用2,6-二碘-1,3,5,7-四甲基-8-苯基-4,4-二氟硼二氮杂萘（）和乙氧基柱[5]芳烃（）合成了一种-功能化柱[5]芳烃（），还制备了用作客体分子的含氰基的（），并用于研究和部分之间的电子转移机制以及减弱部分的TTA效应。前沿分子轨道和自旋密度等值面的理论计算结果初步预测，部分的空腔对单元的荧光发射有影响，但对中的三重态没有影响。在各种不同极性的溶剂中的荧光发射强度和电化学研究表明，存在从到单元的电子转移，并且该电子转移过程对荧光发射有影响，但对中的部分的三重态没有影响，这验证了密度泛函理论计算的结果。在各种溶剂中，在高浓度（1.0×10 M）下，的三重态寿命比和的长，并且的光氧化能力比和的好；相比之下，、和的固有三重态寿命和单线态氧量子产率（Φ）非常相似。这是因为部分的空间位阻可以减弱部分的TTA效应，而不影响它们在中的固有三重态寿命。
