title: Theoretical studies of blue-emitting iridium complexes with different ancillary ligands.
abstract: The structural and electronic properties of two heteroleptic iridium complexes Ir(dfppy)2(pic) (FIrpic) and Ir(dfppy)2(acac) (FIracac) have been investigated theoretically, where dfppy = 2-(2,4-difluorophenyl) pyridine, pic = picolinic acid, and acac = acetoylacetonate. The geometries of ground and excited states are optimized at PBE0/LANL2DZ and CIS/LANL2DZ levels, respectively. Time-dependent density functional theory (TDDFT) method is employed to explore the absorption and emission properties. In the ground state, the highest-occupied molecular orbital has a significant mixture of metal Ir(d) and dfppy(pi), the lowest-unoccupied orbital locates primarily on pi* of pic for FIrpic and pi* of dfppy for FIracac. The luminescence of each complex originates from the lowest triplet excited state, which is assigned to the mixing of metal-to-ligand charge transfer and intraligand charge transfer characters. The effects of ancillary ligands pic and acac on absorption and emission spectra are observed by analysis of TDDFT results. The connection between the nature of excited states and the behavior of the complexes with different ancillary ligands is elucidated.
authors.affiliation: State Key Laboratory of Supramolecular Structure and Materials, Jilin University, Changchun 130012, People's Republic of China.
authors.forename: Xin
authors.initials: X
authors.lastname: Gu
authors.forename: Teng
authors.initials: T
authors.lastname: Fei
authors.forename: Houyu
authors.initials: H
authors.lastname: Zhang
authors.forename: Hai
authors.initials: H
authors.lastname: Xu
authors.forename: Bing
authors.initials: B
authors.lastname: Yang
authors.forename: Yuguang
authors.initials: Y
authors.lastname: Ma
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Liu