NHC-derived carbon-centered luminescent radicals with shortwavelength emission via suppression of Kasha's rule  

作　　者：Can Chen Xin Li Xinhua Ouyang Ying-Feng Han 

机构地区：[1]Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of the Ministry of Education,Xi’an Key Laboratory of Functional Supramolecular Structure and Materials,College of Chemistry and Materials Science,Northwest University,Xi’an 710127,China [2]College of Material Engineering Fujian Agriculture and Forestry University,Fuzhou 350108,China

出　　处：《Science China Chemistry》2024年第8期2679-2685,共7页中国科学（化学英文版）

基　　金：supported by the National Natural Science Fund for Distinguished Young Scholars of China (22025107);the National Youth Top-notch Talent Support Program of China;the National Natural Science Foundation of China (22305190);the Shaanxi Fundamental Science Research Project for Chemistry&Biology (22JHZ003);the Key International Scientific and Technological Cooperation and Exchange Project of Shaanxi Province (2023-GHZD-15);the China Postdoctoral Science Foundation (2022M712573);the Xi’an Key Laboratory of Functional Supramolecular Structure and Materials;the FM&EM International Joint Laboratory of Northwest University。

摘　　要：Luminescent organic radicals have garnered increasing attention owing to their versatile applications in sensing, imaging, and organic light-emitting diodes(OLEDs), attributed to their unique emission properties originating from the doublet spin state.However, the natural narrow bandgap of organic free radicals typically limits their emission to the long-wavelength region.Designing luminescent organic radicals with short-wavelength emission remains a significant challenge. Herein, a series of carbon-centered radicals with short-wavelength emission(383–476 nm) by combining N-heterocyclic carbenes with various polycyclic aromatic hydrocarbons(PAHs)(2-naphthyl, 2a~Ⅰ and 2b~Ⅰ;2-phenanthryl, 2a~Ⅱand 2b~Ⅱ;2-anthryl, 2a~Ⅲand 2b~Ⅲ;3-phenanthryl, 2a~Ⅳand 2b~Ⅳ). Theoretical calculations reveal that the introduction of PAHs significantly increases the ΔE_(D2-D1) in 2a^(Ⅰ–Ⅲ)and 2b^(Ⅰ–Ⅲ)compared to that in phenyl-derived radical congeners. Consequently, the internal transition from D2 to D1 is impeded, leading to a high yield of D2 emission and a suppressed Kasha's rule, thereby overcoming the limitations imposed by their narrow bandgap. For 2a~Ⅳ and 2b~Ⅳ, despite a moderately large ΔED2-D1value, the ΔED3-D1value exceeds 1 e V, indicating that their emission likely originates from the D3 state. Furthermore, we utilized 2a~Ⅲand 2b~Ⅲ as emissive materials in OLEDs,resulting in blue emissions with external quantum efficiencies of 7.5% and 6.5%, respectively.

关 键 词：N-heterocyclic carbenes luminescent organic molecules carbon-centered radicals short-wavelength emission 

分 类 号：O644.1[理学—物理化学]