A theoretical analysis of the effects of electron-withdrawing substitutions on electronic structures and phosphorescent efficiency of a series of Ir(III) complexes with 2-phenylpyridine ligands
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A density functional theory and time-dependent density functional theory approaches were used to understand the structure–property relationships of a series of Ir(III) complexes Ir(x-NHC)(y-ppy)2 [where NHC = 2,3-dihydro-1-methyl-3-phenyl-1H-imidazole, ppy = 2-phenylpyridine, x = Cl, y = H (1a); x = Cl, y = Cl (1a-Cl); x = Cl, y = F (1a-F); x = Cl, y = CN (1a-CN); x = Cl, y = CF3 (1a-CF 3 ); x = F, y = CF3 (2-CF 3 )]. The investigations on the electronic structures in the ground and lowest triplet excited states, the frontier molecular orbitals, the absorption and emission spectra, as well as charge injection and transport of these Ir complexes provided a good understanding of the structure–property relationships. Furthermore, the full details of the metal character in the phosphorescent spectra(3MLCT %), triplet energy (E T1), the singlet–triplet splitting energy (ΔE S1–Tn), 3MLCT–3MC energy gap, as well as d orbitals splitting revealed that quantum yield was effectively enhanced by introducing CN and CF3 groups on the ppy ligands. The designed complexes 1-CN, 1-CF 3 , and 2-CF 3 are expected to be highly efficient phosphorescent materials in organic light-emitting diodes.
KeywordsIridium complexes Density functional theory 2-Phenylpyridine
Financial supports from NSFC (Nos. 21243006 and 51304193), the Basic Research Program of Jiangsu Province (No. BK20130172), the Fundamental Research Funds for the Central Universities (No. 2013QNA14). A Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions. We are grateful to the High Performance Computing Center of China University of Mining and Technology for the award of CPU hours to accomplish this work.
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