title: Strongly luminous tetranuclear gold(I) complexes supported by tetraphosphine ligands, meso- or rac-bis[(diphenylphosphinomethyl)phenylphosphino]methane.
abstract: A series of tetragold(I) complexes supported by tetraphosphine ligands, meso- and rac-bis[(diphenylphosphinomethyl)phenylphosphino]methane (meso- and rac-dpmppm) were synthesized and characterized to show that the tetranuclear Au(I) alignment varies depending on syn- and anti-arrangements of the two dpmppm ligands with respect to the metal chain. The structures of syn-[Au4 (meso-dpmppm)2X]X'3 (X = Cl; X' = Cl (4 a), PF6 (4 b), BF4 (4 c)) and syn-[Au4 (meso-dpmppm)2]X4 (X = PF6 (4 d), BF4 (4 e), TfO (4 f); TfO = triflate) involved a bent tetragold(I) core with a counter anion X incorporated into the bent pocket. Complexes anti-[Au4 (meso-dpmppm)2]X4 (X = PF6 (5 d), BF4 (5 e), TfO (5 f)) contain a linearly ordered Au4 string and complexes syn-[Au4 (rac-dpmppm)2X2]X'2 (X = Cl, X' = Cl (6 a), PF6 (6 b), BF4 (6 c)) and syn-[Au4 (rac-dpmppm)2]X4 (X = PF6 (6 d), BF4 (6 e), TfO (6 f)) consist of a zigzag tetragold(I) chain supported by the two syn-arranged rac-dpmppm ligands. Complexes 4 d-f, 5 d-f, and 6 d-f with non-coordinative large anions are strongly luminescent in the solid state (λmax = 475-515 nm, Φ = 0.67-0.85) and in acetonitrile (λmax = 491-520 nm, Φ = 0.33-0.97); the emission was assigned to phosphorescence from (3) [dσ*σ*σ* pσσσ] excited state of the Au4 centers on the basis of DFT calculations as well as the long lifetime (a few μs). The emission energy is predominantly determined by the HOMO and LUMO characters of the Au4 centers, which depend on the bent (4), linear (5), and zigzag (6) alignments. The strong emissions in acetonitrile were quenched by chloride anions through simultaneous dynamic and static quenching processes, in which static binding of chloride ions to the Au4 excited species should be the most effective. The present study demonstrates that the structures of linear tetranuclear gold(I) chains can be modified by utilizing the stereoisomeric tetraphosphines, meso- and rac-dpmppm, which may lead to fine tuning of the strongly luminescent properties intrinsic to the Au(I) 4 cluster centers.
authors.affiliation: Department of Chemistry, Faculty of Science, Nara Women's University, Kitauoya-nishi-machi, Nara, 630-8506 (Japan).
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Tanase
authors.forename: Risa
authors.initials: R
authors.lastname: Otaki
authors.forename: Tomoko
authors.initials: T
authors.lastname: Nishida
authors.forename: Hiroe
authors.initials: H
authors.lastname: Takenaka
authors.forename: Yukie
authors.initials: Y
authors.lastname: Takemura
authors.forename: Bunsho
authors.initials: B
authors.lastname: Kure
authors.forename: Takayuki
authors.initials: T
authors.lastname: Nakajima
authors.forename: Yasutaka
authors.initials: Y
authors.lastname: Kitagawa
authors.forename: Taro
authors.initials: T
authors.lastname: Tsubomura
mesh_terms: D056831:Coordination Complexes / Q000737:chemistry*; D006046:Gold / Q000737:chemistry*; D008024:Ligands; D049449:Luminescence; D049408:Luminescent Agents / Q000737:chemistry*; D008697:Methane / Q000737:chemistry*; D008958:Models, Molecular; D010720:Phosphines / Q000737:chemistry*
chemical_list: D056831:Coordination Complexes; D008024:Ligands; D049408:Luminescent Agents; D010720:Phosphines; D006046:Gold; D008697:Methane
keywords: denisty functional calculations; emission quenching; gold; photochemistry; tetranuclear complexes; tetraphosphine ligand