基于激发态分子内质子转移的三重态光敏剂的研究

Recently，much attention has been focused on the study of triplet photosensitizers due to their wide applications in the areas of photocatalysis, triplet-triplet annihilation upconversion and photodynamic therapy and so on. However, the existing photosensitizers have some limitations in obtaining triplet excited state，which usually rely on the heavy atoms or spin converters with high efficient intersystem crossing ( ISC ) ability. Previous study shows the population of cis-ketone triplet exited states in the process of ESIPT, thus combination of strong visible absorbance chromophore with the traditional ESIPT dyes which is with cis-ketone triplet exited states to design the heavy-atom free and long-lived organic triplet photosensitizers. And the effects of conjugate and non-conjugate connection on the properties of triplet excited state are also studied. Based on the calculation as auxiliary tool, the driving force of ESIPT is calculated firstly and then the target molecule is selected to be synthesized according to the DFT calculation. We will summarize the method how to use ESIPT process to obtain triplet excited state. And the relevant method for design of such kind of photosensitizers will be illustrated with intensive research on the photophysical properties with steady and time-resolved spectroscopy and DFT calculation. It will provide an innovative method for the design of triplet photosensitizers without heavy atom.

三重态光敏剂被广泛地应用于光催化、三重态–三重态湮灭（TTA）上转换、以及光动力治疗等领域而备受关注。但是现有光敏剂获得三重态的方式还存在一定的局限性，如：三重态的产生有赖于重原子效应，或引入具有高效系间窜越能力的自旋转换单元等。前期研究发现在激发态分子内质子转移（ESIPT）过程中，能够获得cis-酮式结构的三重激发态。本项目将具有强可见光吸收能力的吸光团与传统的具有cis-酮式三重激发态ESIPT染料结合，利用ESIPT光物理过程中产生的三重态，设计不含重原子且具有长寿命的有机三重态光敏剂，并探讨共轭和非共轭的连接方式对三重态性质产生的影响。以量子化学计算为辅助工具，对所设计的分子进行激发态质子转移驱动力进行计算，筛选出目标分子进行合成；通过稳态和瞬态吸收光谱等光物理性质的研究，总结如何利用ESIPT过程设计此类三重态光敏剂并总结相关规律，为设计不含重原子的三重态光敏剂提供创新思路.

近年来，三重态光敏剂由于其在光解水制氢、光动力治疗等领域的广泛应用备受关注。然而现有的三重态光敏剂，获得三重态的方法存在一定局限性，通常有赖于重原子或具有较高系间窜越能力的自选转换单元等。为了解决这一问题，我们提出将具有强可见光吸收能力的吸光团，与传统的具有ESIPT的染料结合，获得不含重原子、具有长寿命三重态的光敏剂。研究内容主要包括：① 设计合成了NDI和HBT通过共轭和非共轭两种连接方式，不含重原子的新型三重态光敏剂；② 获得了新型ESIPT的三重态光敏剂N-1，且具有长寿命三重态(三重态寿命为72.0 μs)；非共轭连接的N-4无ESIPT, 但具有更长寿命的三重态(三重态寿命为148.0 μs)；③ 在NDI中引入供电子基（烷氨基）不利于ESIPT的产生（如：N-2）；④氨基取代的苝酰二亚胺和HBT通过共轭方式连接所获得的化合物P-1和P-2并没有产生ESIPT,此类化合物具有近红外吸收和发光；同时具有大Stokes位移，并通过DFT量化计算解释了其产生的主要原因是，由于由基态到激发态过程产生的构型松弛。