Reductive Coupling of Diynes at Rhodium Gives Fluorescent Rhodacyclopentadienes or Phosphorescent Rhodium 2, 2’-Biphenyl Complexes

Carolin Sieck, Meng Guan Tay, Dr. Marie-Hélène Thibault, Dr. Robert M. Edkins, Dr. Karine Costuas, Prof. Jean-François Halet, Dr. Andrei S. Batsanov, Dr. Martin Haehnel, Dr. Katharina Edkins, Dr. Andreas Lorbach, Dr. Andreas Steffen, Prof. Todd B. Marder

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Abstract

Reactions of [Rh(κ2-O,O-acac)(PMe3)2] (acac=acetylacetonato) and α,ω-bis(arylbutadiynyl)alkanes afford two isomeric types of MC4 metallacycles with very different photophysical properties. As a result of a [2+2] reductive coupling at Rh, 2,5-bis(arylethynyl)rhodacyclopentadienes (A) are formed, which display intense fluorescence (Φ=0.07–0.54, τ=0.2–2.5 ns) despite the presence of the heavy metal atom. Rhodium biphenyl complexes (B), which show exceptionally long-lived (hundreds of μs) phosphorescence (Φ=0.01–0.33) at room temperature in solution, have been isolated as a second isomer originating from an unusual [4+2] cycloaddition reaction and a subsequent β-H-shift. We attribute the different photophysical properties of isomers A and B to a higher excited state density and a less stabilized T1 state in the biphenyl complexes B, allowing for more efficient intersystem crossing S1→Tn and T1→S0. Control of the isomer distribution is achieved by modification of the bis- (diyne) linker length, providing a fundamentally new route to access photoactive metal biphenyl compounds.
Original languageEnglish
Pages (from-to)10523-10532
JournalChemistry - A European Journal
Volume22
Issue number30
Early online date29 Jun 2016
DOIs
Publication statusPublished - 18 Jul 2016

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    Sieck, C., Tay, M. G., Thibault, D. M-H., Edkins, D. R. M., Costuas, D. K., Halet, P. J-F., Batsanov, D. A. S., Haehnel, D. M., Edkins, D. K., Lorbach, D. A., Steffen, D. A., & Marder, P. T. B. (2016). Reductive Coupling of Diynes at Rhodium Gives Fluorescent Rhodacyclopentadienes or Phosphorescent Rhodium 2, 2’-Biphenyl Complexes. Chemistry - A European Journal, 22(30), 10523-10532. https://doi.org/10.1002/chem.201601912