Strongly Luminous Tetranuclear Gold(I) Complexes Supported by Tetraphosphine Ligands,meso‐ or rac‐Bis[(diphenylphosphinomethyl)phenylphosphino]methane |
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| Authors: | Prof Tomoaki Tanase Risa Otaki Tomoko Nishida Hiroe Takenaka Dr Yukie Takemura Prof Bunsho Kure Prof Takayuki Nakajima Prof Yasutaka Kitagawa Prof Taro Tsubomura |
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| Affiliation: | 1. Department of Chemistry, Faculty of Science, Nara Women's University, Kitauoya‐nishi‐machi, Nara, 630‐8506 (Japan);2. Department of Chemistry, Graduate School of Science, 1‐1 Machikaneyama, Toyonaka, Osaka 560‐0043 (Japan);3. Department of Materials and Life Science, Seikei University, 3‐3‐1 Kichijoji‐kitamachi, Musashino, Tokyo 180‐8633 (Japan) |
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| 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 AuI 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 3dσ*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 AuI4 cluster centers. |
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| Keywords: | denisty functional calculations emission quenching gold photochemistry tetranuclear complexes tetraphosphine ligand |
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