Reductive coupling of diynes at rhodium gives fluorescent rhodacyclopentadienes or phosphorescent rhodium 2,2’-biphenyl complexes

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

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9 Citations (Scopus)

Abstract

Reactions of [Rh(κ2-O,O-acac)(PMe3)2] (acac=acetylacetonato) and α,ω-bis(arylbutadiynyl)alkanes afford two isomeric types of MC4metallacycles 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 T1state in the biphenyl complexes B, allowing for more efficient intersystem crossing S1→Tnand 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
Number of pages10
JournalChemistry - A European Journal
Volume22
Issue number30
DOIs
Publication statusPublished - 1 Jan 2016

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Keywords

  • dibenzo ligands
  • intersystem crossing
  • luminescence
  • metallacycles
  • OLEDs
  • rhodium complexes

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