Deep Blue Phosphorescence from Platinum Complexes Featuring Cyclometalated N-Pyridyl Carbazole Ligands with Monocarborane Clusters (CB11H12-)

Yunjun Shen; Xiangjun Kong; Fengjie Yang; He-Dong Bian; Gang Cheng; Timothy R Cook; Yuzhen Zhang

doi:10.1021/acs.inorgchem.2c02467

Deep Blue Phosphorescence from Platinum Complexes Featuring Cyclometalated N-Pyridyl Carbazole Ligands with Monocarborane Clusters (CB₁₁H₁₂^-)

Inorg Chem. 2022 Oct 24;61(42):16707-16717. doi: 10.1021/acs.inorgchem.2c02467. Epub 2022 Oct 7.

Authors

Yunjun Shen¹, Xiangjun Kong¹, Fengjie Yang¹, He-Dong Bian¹, Gang Cheng², Timothy R Cook³, Yuzhen Zhang¹

Affiliations

¹ Key Laboratory of Chemistry and Engineering of Forest Products, State Ethnic Affairs Commission, Guangxi Key Laboratory of Chemistry and Engineering of Forest Products, Guangxi Collaborative Innovation Center for Chemistry and Engineering of Forest Products, School of Chemistry and Chemical Engineering, Guangxi Minzu University, No. 158, Daxue West Road, Nanning, Guangxi 530006, China.
² State Key Laboratory of Synthetic Chemistry, HKU-CAS Joint Laboratory on New Materials, Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, China.
³ Department of Chemistry, University at Buffalo, The State University of New York, 856 Natural Sciences Complex, Buffalo, New York 14260, United States.

PMID: 36205461
DOI: 10.1021/acs.inorgchem.2c02467

Abstract

The utilization of deep blue phosphorescent materials in high-performance displays and solid-state lighting requires high quantum efficiencies and color purities. Here, we describe the preparation and luminescent properties of novel platinum triplet emitters featuring cyclometalated N-pyridyl-carbazole ligands functionalized with closo-monocarborane clusters [CB₁₁H₁₂]^-. All reported complexes were fully characterized by using standard small molecule techniques (UV-vis, cyclic voltammetry, nuclear magnetic resonance (NMR), high-resolution mass spectrometry (HRMS)), and their solid-state structures were elucidated by X-ray diffraction. These platinum phosphors emit in the blue region of the visible wavelength spectrum in both the solid and solution states. Complex 4a exhibits the highest luminous efficiency at λ_em = 439 nm with a photoluminescent quantum yield (PLQY) of 60% by dispersing in a PMMA matrix. Electrochemical and computational studies of complexes 4a and 4b revealed that the blue phosphorescence originates mainly from intraligand ³π → π* (³ILCT) transitions with relatively small ³MLCT mixing. A deep-blue OLED containing 4a as the light-emitting dopant was successfully fabricated using a solution-processed method, and the device exhibited blue photoluminescence with CIE coordinates of (0.17, 0.15) and a maximum external quantum efficiency (EQE_max) value of 6.2%. This article represents the pioneering study of a deep blue PhOLED using a Pt complex bearing a closo-monocarborane anion substituent, providing a new avenue into the preparation of novel triplet emitters based on boron-rich cluster anions.