调控三重态能级构筑新型较强发光效率的长寿命铜配合物---分子设计、合成及光学特性

Cu(I) complexes have attracted considerable attention in a variety of applications such as solar cells, ionic probe, biological sensing, and photocatalysis owing to their abundant, inexpensive, and less toxic properties. Furthermore, the desirable properties of their long excited-state lifetimes and high luminescent quantum efficiencies are essential for enhancing the application effect. However, how to achieve longer excited-state lifetimes while maintaining higher luminescent quantum efficiencies are challenging and the relevant studies are still lacking. With the aim to solve the above questions, in this project, the thermal reversible energy equilibrium between the 3MLCT triplet emissive state of Cu(I) complexes based on the five-ring ligands and 3IL(3LLCT) triplet state of an organic chromophore based on anthanence or their derivatives can be established if the newly introduced triplet level of the organic chromophore attached to metal complexes was essentially isoenergetic with the level of 3MLCT state, and the 3IL or 3LLCT state was served as an “energy reservoir”, leading to a lengthening of the observed excited lifetime, while with a luminescence quantum yield similar to that of the parent complex. Variations in the electrical properties, substituent positions, and linkage modes will be varied to manipulate the energy level of triplet 3MLCT and 3IL/3LLCT states systematically to investigate the change of the photophysical properties of complexes. Absorption spectra, emission spectra, transient spectra, excited-state lifetime and quantum efficiency measurement will be employed to explore the molecular design rule of Cu(I) complexes with the properties of long excited-state lifetimes and high luminescent quantum efficiencies, which is of great significance for the practical application.

含量丰富、价格低廉、低毒性的过渡金属Cu(I)配合物在太阳能电池、离子探针、生物检测及光敏剂催化领域有着广阔的应用前景，而具有长寿命、较强发光特性对提高应用效果至关重要。但如何获取长寿命和较高的发光量子效率，研究还很不充分。本项目拟采用五元氮杂环配体类Cu配合物为母体，引入改性的蒽类有机发色基团，通过发色基团的3IL/3LLCT 态与铜配合物的3MLCT 态能级平衡，形成3IL/3LLCT激发态作为一个“贮藏库”来导致持续的3MLCT激发态恢复，实现Cu(I)配合物的长激发态寿命，同时保持较好的发光效率。将系统考察不同电子特性、不同取代位置、不同连接方式在调控三重态3MLCT和3IL/3LLCT态时其发光行为的变化规律。通过研究吸收光谱、发射光谱、瞬态光谱、激发态寿命和量子效率等光物理特性，探索实现长寿命、较强发光效率Cu(I)配合物分子设设计的规律和方法，这无疑对于实际应用具有重要意义。

强吸收、长寿命的铜配合物在太阳能电池转换、离子检测、生物探针、发光二极管等领域有着非常广阔的应用前景。但铜配合物在可见光区的吸收一般来说都较弱，光激发时无法吸收更多的能量，限制了其应用。因此制备具有强吸收，同时又拥有较长激发态寿命的铜配合物仍然具有重要的理论和实际应用价值。我们研究的主要内容是基于邻菲罗啉和吡啶咪唑类配体结构，通过各种电子结构基团的引入和增大共轭效应和来改变配合物的结构和能级水平，来实现吸收的增强和发光寿命的延长。取得如下重要结果或发现：（1）、芴分子的加入，极大提高了配合物的光吸收能力，相比没有引入芴基团的配合物而言，摩尔吸光系数从2630 M-1 cm-1增加到5400 M-1 cm-1，发光寿命更是增加了近4倍，达到了51.2微秒；（2）、具有较大共轭性的苯、萘和菲的引入，使配合物的光吸收能力有了很大的提高，最低吸收峰的摩尔吸光系数（380nm处）从1300左右增加到14000左右，实现了长寿命、较强发光效率的设计目标；（3）、炔键的引入增大了共轭程度，光吸收能力大幅增加，最高达到22000 M-1 cm-1，寿命处在80毫秒左右。通过三重态能级的调控，实现了3MLCT态向3LLCT态的转化，保持了较高的发光效率，为我们设计合成长寿命、较强发光效率的通配合物提供了新的思路。项目执行四年来，在Eur. J. Inorg. Chem、Inorg. Chim. Acta、J. Photochem. Photobiol. A. Chem.等期刊上发表SCI论文7篇（第一标注）, 4篇（第二标注），3篇（第三标注）。申请发明专利2项。培养硕士研究生8名，其中已毕业4名，硕士在读4名，已经全面完成既定目标。