N1取代基结构对菲并咪唑荧光色纯度的影响

以1,2-二苯基菲并咪唑(PPI)为模型化合物, 通过改变N1苯环上取代基结构制备了2类PPI衍生物, 并采用核磁共振谱对其化学结构进行了确认. 通过对PPI及其衍生物的单分子荧光光谱精细结构的分析, 比较了取代基位置和结构的变化对菲并咪唑类化合物荧光过程中发射主峰精细振动结构及所占比例的影响. 其中, N1链接苯环中R4位的取代基效应最显著, 当引入推电子或弱的吸电子取代基时, 菲并咪唑类衍生物的低能级发射比例降低, 荧光色纯度提高; 当引入强吸电子取代基时, 低能级发射比例增加, 光谱半峰宽加大. 本文结果为菲并咪唑基“蓝光”材料的设计提供了一定数据的支持与科学依据.

Effects on Fluorescence Color Purity of Phenanthroimidazole Derivatives from N1 Substituted Group†

Phenanthro9,10-d]imidazole(PI), as a new class building block for organic blue fluorescence emitter, has attracted more and more attention due to its potential application of highly efficient non-doped blue materials and white or phosphorescent host, but it is a pity with a little reports in its structure-property relationship, such as color purity. Owing to the substituted group at C2-position participating in the formation of the frontier molecular orbitals in the obtained materials, tremendous attentions is cost to tune the stuctures at this position, another key factor to their emitting light color from N1 position was ignored. In this paper, 1,2-diphenyl-1H-phenanthro9,10-d]imidazole(PPI) was chosen as a model compound for PI-based compound, and its two kinds of derivatives were prepared by tuning the substituted group in phenyl attached N1-position. Their basic chemical structures were confirmed by NMR spectra. Comparing with the fine fluorescence spectra in single molecular of PPI and its derivatives, the shift regulation of the various level emission peaks and their proportion to PI unit was carefully disclosed by changing the substituted position and structure. Here, R4-substituted position in phenyl attached N1 played more important role in substituent effect than others. When the electron-donating substituent or weak electron-withdrawing group was introduced to this position, the proportion of low-energy level emission decrease in fine fluorescence spectra of PI block, and the color purity was improved obviously. When the stronger electron-withdrawing group was inserted, the proportion of low-energy level emission increased in fine fluorescence spectra and the peak width was expended. All of these results could provide some basal theory for design of various blue emitters based on PI block.