三重态-三重态湮灭上转换的纯有机三重态光敏剂和三重态能量受体的研究

Triplet-triplet annihilation (TTA) based upconversions are particularly interesting, for which non-coherent excitation with low power density is sufficient. Furthermore, TTA upconversion shows strong absorption of excitation light, high upconversion quantum yield and readily tunable operational wavelength, etc. However, this newly developed upconversion scheme is facing a few challenges. First, currently the triplet photosensitizers for TTA upconversion is limited to the transition metal complexes, such as the Pt(II), Ir(III) or Ru(II) complexes. Heavy atom-free organic triplet photosensitizers will be the alternatives to replace the transition metal complex photosensitizers, but organic triplet photosensitizers for TTA upconversion are rarely reported because it is very difficult for the triplet excited state populated for the heavy atom-free organic chromophores. Second, the amount of the triplet acceptors for TTA upconversion is limited, and the current triplet acceptors are based on single chromophore, thus the TTA is intermolecular process. In order to address these fundamental problems of the development of TTA upconversion and for its future application in photocatalysis, photovoltaics, etc, based on our study on TTA upconversion, herein we will design organic triplet photosensitizers based on C60-organic chromophore (BODIPYs are used) dyads. These new organic triplet photosensitizers are free of any heavy atoms and the photophysical properties can be readily tuned (such as the absorption wavelength). Most importantly, the ISC property of the C60-BODIPY dyads are predictable, thus this is a general molecular structure motif for organic triplet photosensitizers that show strong absorption of visible light and it will be useful for not only TTA upconversion, but also for photocatalysis and photovoltaics, etc. Second, we will design "dimer" triplet acceptor, in which two triplet acceptor units are connected together by covalent bond. Thus the previous "intermolecular" TTA process will be transformed to a more efficient "intramolecular" process. As a result, the TTA efficiency can be improved.These fundamental investigations will be important for improvement of the TTA upconversion efficiency at molecular level, as well as for the future applications of the TTA upconversion for luminescent bioimaging, photocatalysis and photovoltaics, etc.

三重态-三重态湮灭（TTA）上转换具有所需激发光强度低(非相干光、太阳光即可)、上转换量子效率高、吸光能力强、工作波长可调等优点，是一种新的极具发展前途的上转换方法。目前该领域有两个基本科学问题急待解决，（1）设计并制备具有强可见光吸收的有机三重态光敏剂，以取代当前的贵金属配合物三重态光敏剂；并找到一种有机三重态光敏剂的"普适性"分子结构；（2）急需新的高效三重态受体，以提高TTA上转换的量子效率。本申请者计划在前期工作的基础上，针对上述TTA上转换的基本科学问题，设计、合成一系列不含任何贵金属和溴、碘等重原子的、具有强可见光吸收能力的C60-BODIPY Dyad做为有机三重态光敏剂，用于TTA上转换，同时解决新型有机三重态光敏剂难以设计、合成这个光化学领域长期存在的难题；此外，将合成含两个发色团的新型三重态受体，将传统的分子间TTA转变为更高效的分子内TTA，进而提高上转换的量子效率。

三重态-三重态湮灭（TTA）上转换具有所需激发光强度低(太阳光即可)、上转换量子效率高、吸光能力强、工作波长可调等优点，是一种新的极具发展前途的上转换方法。针对目前该领域的两个基本科学问题：（1）如何设计并制备具有强可见光吸收的有机三重态光敏剂，以取代贵金属配合物三重态光敏剂；并找到一种有机三重态光敏剂的“普适性”分子结构；（2）如何设计制备新的高效三重态受体，以提高TTA 上转换的量子效率。本项目开展了以下研究：在前期工作的基础上，设计、合成一系列不含任何贵金属和溴、碘等重原子的、具有强可见光吸收能力的C60-BODIPY Dyad 以及C60-NDI (NDI: 萘酰二亚胺）做为有机三重态光敏剂，用于TTA 上转换，解决了新型有机三重态光敏剂难以设计、合成这个光化学领域长期存在的难题；同时，该类光敏剂还可用于光催化有机合成反应，本项目利用制备的新型有机光敏剂，利用光催化氧化、氮杂Henry反应、以及四氢异喹啉的氧化环加成反应等，与传统的贵金属光敏剂相比，大幅提高了催化效率、缩短了反应时间；此外，合成了一系列含两个发色团的新型三重态能量受体，优化了三重态受体的激发态能级，提高了三重态湮灭的效率，以及三重态湮灭上转换的效率。在以上研究的基础上，本项目还对三重激发态的调控进行了预研，即利用光、化学物质（如具有生物活性的小分子如巯基氨基酸、H2O2、NO等）对分子的三重态实现了开、关的调控，在靶向光动力治疗、可激活的上转换等领域具有一定的意义，并发现三重态的调控规律和单重态的有所不同。在SCI检索期刊共发表论文63篇，如J. Am. Chem. Soc. (2篇)、Chem. Soc. Rev. (2篇)、Chem. Sci. (2篇)、Chem. Commun. (6篇)、Chem.-Eur. J. (2篇)、J. Phys. Chem. (7篇)、Inorg. Chem. (3篇)、J. Mater. Chem. (10篇)、Dalton Trans. (8篇)、J. Org. Chem. (9篇)等期刊上。共做8个国际会议邀请报告（其中瑞典召开的国际会议为特邀报告Keynote Lecture）；共培养6名博士毕业生、6名硕士毕业生，一名博士生获2013年辽宁省优秀博士学位论文奖励（籍少敏）；两名硕士生获辽宁省优秀硕士学位论文奖励（杨佩、贾惠如）。

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