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

Sieck, C.; Tay, M.G.; Thibault, M.-H.; Edkins, R.M.; Costuas, K.; Halet, J.-F.; Batsanov, A.S.; Haehnel, M.; Edkins, K.; Lorbach, A.; Steffen, A.; Marder, T.B.M.

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[RIGHTWARDS ARROW]Tn and T1[RIGHTWARDS ARROW]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

Citation

Sieck, C., Tay, M., Thibault, M., Edkins, R., Costuas, K., Halet, J., …Marder, T. (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

• Journal Article Type: Article
• Acceptance Date: Apr 24, 2016
• Online Publication Date: Jun 29, 2016
• Publication Date: Jul 18, 2016
• Deposit Date: Jun 16, 2016
• Publicly Available Date: Jun 29, 2017
• Journal: Chemistry - A European Journal
• Print ISSN: 0947-6539
• Electronic ISSN: 1521-3765
• Publisher: Wiley
• Peer Reviewed: Peer Reviewed
• Volume: 22
• Issue: 30
• Pages: 10523-10532
• DOI: https://doi.org/10.1002/chem.201601912
• Public URL: https://durham-repository.worktribe.com/output/1380830