基于激发态配位骨架形变受阻的Pt(II)配合物磷光聚集诱导发光分子及电致发性能研究

In traditional phosphorescent complexes with aggregation-induced emission (AIE) features, the phosphorescent AIE mechanisms involved are typically derived from the ones working in the organic fluorescent AIEgens. Obviously, it will set serious restrictions on the design and synthesis novel phosphorescent AIEgens as well as their application. Based on the systematic analysis of the predicaments and pressing problems in both the mechanism investigation of phosphorescent AIEgens and their application in organic electroluminescent field, the novel phosphorescent AIE mechanism has been established based on restraining the D2d distortion of coordinating skeleton in excited states of four-coordinated planar Pt(II) complexes. Based on this new phosphorescent AIE mechanism and combining with functional notion of molecular design, novel phosphorescent AIEgens of the ppy-type Pt(II) complexes with planar four-coordinated configuration have been developed to cope with the problems faced by the traditional phosphorescent AIEgens for their application in organic light-emitting diodes (OLEDs). Furthermore, the relationship between chemical structures of these ppy-type Pt(II) phosphorescent AIEgens and their AIE behaviors as well as their electroluminescent properties will be explored in depth. This research project not only can provide new theoretical basis for the design of novel phosphorescent AIEgens, but also shows great importance for developing highly efficient phosphorescent AIEgens for the application in electroluminescent field.

配合物磷光聚集诱导发光（Aggregation-Induced Emission，AIE）机理过多沿袭传统有机荧光AIE机理，对新型配合物磷光AIE分子的设计合成及相关应用造成严重制约。在对配合物磷光AIE机理研究及其在有机电致发光领域应用所面临的困境和亟待解决问题的系统梳理之上，本项目利用平面4配位Pt(II)配合物骨架从基态平面构型到激发态四面体构型转变（D2d形变）这一特性，发展基于激发态配位骨架D2d形变受阻的磷光AIE新机理，并结合功能化的分子设计合成新型2-苯基吡啶类平面4配位Pt(II)配合物磷光AIE分子，突破配合物磷光AIE分子在电致发光领域应用遇到的瓶颈。在此基础之上，深入探讨基于此磷光AIE新机理的配合物磷光AIE行为、电致发光性能与其结构间的构-效关系规律。本研究不仅为配合物磷光AIE分子设计提供新理论依据，而且对高效磷光AIE电致发光材料的开发也具有重要应用价值。

配合物聚集诱导磷光（AIPE）发光分子以其特殊的发光特性在诸多领域都有重要的应用，尤其是在有机发光二级管（OLED）领域。但是，目前AIPE配合物发光分子的设计原理主要沿袭传统荧光聚集诱导发光（AIE）分子的设计策略，这显然对AIPE配合物发光分子的性能优化产生严重制约，且作为OLED新型发光材料电致发光（EL）效率低，限制了其在EL领域的应用。本项目针对这些关键问题，基于平面4配位Pt(II)配合物分子的结构特点，提出了配位骨架形变受阻的新型AIPE分子设计原理，并结合功能化的分子设计思想，制备并开发出基于新型AIPE配合物发光分子，实现电致发光性能的显著提升。以PtII(C^N)(N-donor ligand)型配合物为对象，利用这类配合物分在溶液中光激发时配位骨架会从基态的平面四边形构型（D4h）转变成激发态的四面体构型（Td）这一配位骨架形变过，猝灭磷光发射信号造成溶液样品的磷光发射信号很弱。然而，在聚集态时配体骨架形变过程会受阻使得磷光发射信号恢复，从而出现AIPE行为。显然，激发态配位骨架形变受阻的AIPE机理完全利用了配合物分子本身的结构特点。同时，通过在配体中引入载流子注入传输功能基团，使得这类新型AIPE配合物发光分子表现出优异的电致发光效率，最大外量子效率为25.2%、电流效率53.9 cd A-1及功率效率43.5 lm W-1。电致发光性能可完全媲美传统配合物磷光分子，解决了传统AIPE配合物分子电致发光效率低的问题。本项目不仅为设计合成新型AIPE配合物分子提出了新的机理，而且为优化AIPE配合物分子性能提供重要的出路。