溶剂极性对D-A-D型延迟荧光分子电荷转移激发态的调控  

Solvent polarity dependence on excited charge-transfer state properties in donor-acceptor-donor thermally activated delayed-fluorescence molecule

作　　者：何桂营 匡卓然 王娴[1,2] 宋宏伟 郭前进 夏安东[1,2] Guiying He1,2, Zhuoran Kuang1,2, Xian Wang1,2, Hongwei Song1,2, Qianjin Guo1., Andong Xia1,2.(1 Beijing National Laboratory for Molecular Scwnces （BNLMS） and Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China 2University of Chinese Academy of Sciences, Beijing 100049, China)

机构地区：[1]中国科学院化学研究所光化学院重点实验室北京分子科学国家实验室,北京100190 [2]中国科学院大学,北京100049

出　　处：《中国科学：化学》2018年第2期210-217,共8页SCIENTIA SINICA Chimica

基　　金：国家自然科学基金(编号:21333012;21373232);国家重点基础研究发展计划(编号:2013CB834604)资助项目

摘　　要：■二唑基四极分子(2,5-bis(4-(10H-phenoxazin-10-yl)phenyl-1,3,4-oxadiazole,2PXZ-OXD)具有典型的电子给体(donor)-受体(acceptor)-给体(donor)(D-A-D)的结构特点,表现出优良的延迟荧光特性.我们利用稳态、瞬态光谱方法研究了该分子在不同极性溶剂中的光物理特性,发现随着溶剂极性的增加,Stokes位移明显增加,证明了光激发下2PXZ-OXD分子产生了强偶极性的电荷转移态.进一步的量化计算结果发现,单重激发态的偶极矩显著大于三重激发态的偶极矩,溶剂极性对单重激发态的影响更大.溶剂极性的增加,打破了四极分子的对称性,促进了单重态能级的下降,从而调控单-三重态间能级差,导致延迟荧光特性的改变.溶剂极性在对单重态与三重态的能级差调控的同时,也会对2PXZ-OXD分子的发射振子强度有影响,强极性造成的显著非辐射弛豫过程会明显降低发光性能.The photophysical properties of a donor-acceptor-donor（D-A-D） molecule based on oxadiazole,2,5-bis（4-（10 H-phenoxazin-10-yl）phenyl-1,3,4-oxadiazole（2 PXZ-OXD）, have been systematically investigated by means of steady state and transient spectroscopy. A significant increase of Stokes shift with increasing solvent polarity indicates that a dipolar charge-transfer state is produced upon excitation. Further quantum chemical calculations show that the dipole moment of singlet excited state is much larger than that of triplet excited state, where singlet excited state is much more dependent on the polarity of solvents. The symmetry-breaking charge transfer states of quadrupole molecule induced by solvent polarity, exhibit large energy loss of singlet state with increasing of polarity. The energy gap is controlled by solvent polarity because of solvation. Furthermore, the emissive oscillator strength is dependent on the polarity, and the non-emissive relaxation resulted from the strong solvation reduces the luminescence properties of emitter.

关 键 词：电荷转移 延迟荧光 溶剂化 

分 类 号：O621.22[理学—有机化学]