Regioselective Syntheses of Imidazo[4,5- b]pyrazin-2-ylidene-Based Chelates and Blue Emissive Iridium(III) Phosphors for Solution-Processed OLEDs

Jie Yan; Qin Xue; Hui Yang; Shek-Man Yiu; Ye-Xin Zhang; Guohua Xie; Yun Chi

doi:10.1021/acs.inorgchem.2c00750

Regioselective Syntheses of Imidazo[4,5- b]pyrazin-2-ylidene-Based Chelates and Blue Emissive Iridium(III) Phosphors for Solution-Processed OLEDs

Inorg Chem. 2022 Jun 13;61(23):8797-8805. doi: 10.1021/acs.inorgchem.2c00750. Epub 2022 Jun 2.

Authors

Jie Yan¹, Qin Xue², Hui Yang¹, Shek-Man Yiu¹, Ye-Xin Zhang³, Guohua Xie⁴, Yun Chi¹

Affiliations

¹ Department of Materials Science and Engineering, Department of Chemistry, Center of Super-Diamond and Advanced Films (COSDAF), City University of Hong Kong, Kowloon 999077, Hong Kong SAR, China.
² Department of Physical Science and Technology, Central China Normal University, Wuhan 430079, China.
³ Suzhou Joysun Advanced Materials Co., Ltd., Suzhou 215126, Jiangsu, China.
⁴ Sauvage Center for Molecular Sciences, Hubei Key Lab on Organic and Polymeric Optoelectronic Materials, Department of Chemistry, Wuhan University, Wuhan 430072, China.

PMID: 35652376
DOI: 10.1021/acs.inorgchem.2c00750

Abstract

Six homoleptic Ir(III) complexes bearing imidazo[4,5-b]pyrazin-2-ylidene chelates were successfully designed and synthesized. Narrowband blue emission (λ_max = 466-485 nm) and broadened green emission (λ_max = 518-532 nm) in degassed toluene solution with high photoluminescent quantum yields in the range of 75-81 and 45-48% were observed for f-timpz, t2impz, and t2empz as well as m-timpz, t2impz, and t2empz, respectively. In addition, the tert-butylphenyl cyclometalate is more electron donating than N-phenyl cyclometalate and, hence, all tert-butylphenyl-substituted derivatives, that is, m- and f-t2impz and m- and f-t2empz, give more red-shifted emission in comparison to that of m- and f-timpz. Moreover, solution-processed OLED with f-t2empz (20 wt %) as the dopant gave electrophosphorescence at 474 nm with maximum external quantum efficiency (max. EQE) of 5.1%, while hyper-OLED with assistant sensitizer f-t2empz (10 wt %) and the multi-resonance thermally activated delayed fluorescence emitter BCzBN (0.5 wt %) afforded narrowband emission centered at 485 nm and max. EQE up to 17.4%, confirming the high potential of this class of Ir(III) metal phosphors.