title: Highly Efficient Thermally Activated Delayed Fluorescence in Dinuclear Ag(I) Complexes with a Bis-Bidentate Tetraphosphane Bridging Ligand.
abstract: A series of highly emissive neutral dinuclear silver complexes [Ag(PPh3)(X)]2(tpbz) (tpbz = 1,2,4,5-tetrakis(diphenylphosphanyl)benzene; X = Cl (1), Br (2), I (3)) was synthesized and structurally characterized. In the complexes, the silver atoms with tetradedral geometry are bridged by the tpbz ligand, and the ends of the molecules are coordinated by a halogen anion and a terminal triphenylphosphine ligand for each silver atom. These complexes exhibit intense white-blue (λmax= 475 nm (1) and 471 nm (2)) and green (λmax= 495 nm (3)) photoluminescence in the solid state with quantum yields of up to 98% (1) and emissive decay rates of up to 3.3 × 105s-1(1) at 298 K. With temperature decreasing from 298 to 77 K, a red shift of the emission maximum by 9 nm for all these complexes is observed. The temperature dependence of the luminescence for complex 1 in solid state indicates that the emission originates from two thermally equilibrated charge transfer (CT) excited states and exhibits highly efficient thermally activated delayed fluorescence (TADF) at ambient temperature. At 77 K, the decay time is 638 μs, indicating that the emission is mainly from a triplet state (T1state). With temperature increasing from 77 to 298 K, a significant decrease of the emissive decay time by a factor of almost 210 is observed, and at 298 K, the decay time is 3.0 μs. The remarkable decrease of the decay time indicates that thermal population of a short-lived singlet state (S1state) increases as the temperature increases. The charge transfer character of the excited states and TADF behavior of the complexes are interrogated by DFT and TDDFT calculations. The computational results demonstrate that the origin of TADF can be ascribed to1,3(ILCT + XLCT+ MLCT) states in complexes 1 and 2 and1,3(XLCT) states mixed with minor contributions of MLCT and ILCT in complex 3.
authors.affiliation: College of Life Science, University of Fujian Agriculture and Forestry , Fuzhou, Fujian 350002, China.
authors.forename: Jin
authors.initials: J
authors.lastname: Chen
authors.affiliation: Key Laboratory of Design and Assembly of Functional Nanostructures, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences , Fuzhou, Fujian 350002, China.
authors.forename: Teng
authors.initials: T
authors.lastname: Teng
authors.affiliation: Key Laboratory of Design and Assembly of Functional Nanostructures, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences , Fuzhou, Fujian 350002, China.
authors.forename: Liju
authors.initials: L
authors.lastname: Kang
authors.affiliation: Key Laboratory of Design and Assembly of Functional Nanostructures, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences , Fuzhou, Fujian 350002, China.
authors.forename: Xu-Lin
authors.initials: XL
authors.lastname: Chen
authors.affiliation: Key Laboratory of Design and Assembly of Functional Nanostructures, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences , Fuzhou, Fujian 350002, China.
authors.forename: Xiao-Yuan
authors.initials: XY
authors.lastname: Wu
authors.affiliation: Key Laboratory of Design and Assembly of Functional Nanostructures, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences , Fuzhou, Fujian 350002, China.
authors.forename: Rongmin
authors.initials: R
authors.lastname: Yu
authors.affiliation: Key Laboratory of Design and Assembly of Functional Nanostructures, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences , Fuzhou, Fujian 350002, China.
authors.forename: Can-Zhong
authors.initials: CZ
authors.lastname: Lu