title: Theoretical characterization and design of highly efficient iridium (III) complexes bearing guanidinate ancillary ligand.
abstract: A density functional theory/time-depended density functional theory was used to investigate the synthesized guanidinate-based iridium(III) complex [(ppy)2Ir{(N(i)Pr)2C(NPh2)}] (1) and two designed derivatives (2 and 3) to determine the influences of different cyclometalated ligands on photophysical properties. Except the conventional discussions on geometric relaxations, absorption and emission properties, many relevant parameters, including spin-orbital coupling (SOC) matrix elements, zero-field-splitting parameters, radiative rate constants (kr) and so on were quantitatively evaluated. The results reveal that the replacement of the pyridine ring in the 2-phenylpyridine ligand with different diazole rings cannot only enlarge the frontier molecular orbital energy gaps, resulting in a blue-shift of the absorption spectra for 2 and 3, but also enhance the absorption intensity of 3 in the lower-energy region. Furthermore, it is intriguing to note that the photoluminescence quantum efficiency (ΦPL) of 3 is significantly higher than that of 1. This can be explained by its large SOC value<T1|HSO|Sn>(n=3-4) and large transition electric dipole moment (μS3), which could significantly contribute to a larger kr. Besides, compared with 1, the higher emitting energy (ET1) and smaller <S0|HSO|T1>(2) value for 3 may lead to a smaller non-radiative decay rate. Additionally, the detailed results also indicate that compared to 1 with pyridine ring, 3 with imidazole ring performs a better hole injection ability. Therefore, the designed complex 3 can be expected as a promising candidate for highly efficient guanidinate-based phosphorescence emitter for OLEDs applications.
authors.affiliation: Institute of Functional Material Chemistry, Faculty of Chemistry, Northeast Normal University, Changchun 130024, People's Republic of China.
authors.forename: Xin-Yao
authors.initials: XY
authors.lastname: Ren
authors.affiliation: Institute of Functional Material Chemistry, Faculty of Chemistry, Northeast Normal University, Changchun 130024, People's Republic of China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Wu
authors.affiliation: Institute of Functional Material Chemistry, Faculty of Chemistry, Northeast Normal University, Changchun 130024, People's Republic of China.
authors.forename: Li
authors.initials: L
authors.lastname: Wang
authors.affiliation: Institute of Functional Material Chemistry, Faculty of Chemistry, Northeast Normal University, Changchun 130024, People's Republic of China.
authors.forename: Liang
authors.initials: L
authors.lastname: Zhao
authors.affiliation: Institute of Functional Material Chemistry, Faculty of Chemistry, Northeast Normal University, Changchun 130024, People's Republic of China. Electronic address: zhangm914@nenu.edu.cn.
authors.forename: Min
authors.initials: M
authors.lastname: Zhang
authors.affiliation: Institute of Functional Material Chemistry, Faculty of Chemistry, Northeast Normal University, Changchun 130024, People's Republic of China. Electronic address: gengy575@nenu.edu.cn.
authors.forename: Yun
authors.initials: Y
authors.lastname: Geng
authors.affiliation: Institute of Functional Material Chemistry, Faculty of Chemistry, Northeast Normal University, Changchun 130024, People's Republic of China. Electronic address: zmsu@nenu.edu.cn.
authors.forename: Zhong-Min
authors.initials: ZM
authors.lastname: Su
mesh_terms: D003198:Computer Simulation; D056831:Coordination Complexes / Q000737:chemistry*; D006146:Guanidines / Q000737:chemistry*; D007495:Iridium / Q000737:chemistry*; D008027:Light; D049408:Luminescent Agents / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D011789:Quantum Theory; D013816:Thermodynamics
chemical_list: D056831:Coordination Complexes; D006146:Guanidines; D049408:Luminescent Agents; D007495:Iridium
keywords: DFT; Guanidinate; Iridium; OLED; Phosphorescence; Spin-orbital coupling