title: Reductive Coupling of Diynes at Rhodium Gives Fluorescent Rhodacyclopentadienes or Phosphorescent Rhodium 2,2'-Biphenyl Complexes.
abstract: Reactions of [Rh(κ(2) -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.
authors.affiliation: Institut für Anorganische Chemie, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074, Würzburg, Germany.
authors.forename: Carolin
authors.initials: C
authors.lastname: Sieck
authors.affiliation: Department of Chemistry, Durham University, South Road, Durham, DH1 3LE, UK.|Faculty of Resource Science and Technology, Universiti Malaysia Sarawak, 94300, Kota Samarahan, Malaysia.
authors.forename: Meng Guan
authors.identifier: http://orcid.org/0000-0002-1728-1297
authors.initials: MG
authors.lastname: Tay
authors.affiliation: Department of Chemistry, Durham University, South Road, Durham, DH1 3LE, UK.
authors.forename: Marie-Hélène
authors.initials: MH
authors.lastname: Thibault
authors.affiliation: Institut für Anorganische Chemie, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074, Würzburg, Germany.
authors.forename: Robert M
authors.initials: RM
authors.lastname: Edkins
authors.affiliation: Institut des Sciences Chimiques de Rennes, UMR 6226 CNRS, Université de Rennes 1, 35042, Rennes Cedex, France.
authors.forename: Karine
authors.initials: K
authors.lastname: Costuas
authors.affiliation: Institut des Sciences Chimiques de Rennes, UMR 6226 CNRS, Université de Rennes 1, 35042, Rennes Cedex, France.
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Halet
authors.affiliation: Department of Chemistry, Durham University, South Road, Durham, DH1 3LE, UK.
authors.forename: Andrei S
authors.initials: AS
authors.lastname: Batsanov
authors.affiliation: Institut für Anorganische Chemie, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074, Würzburg, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Haehnel
authors.affiliation: School of Medicine, Pharmacy and Health, Durham University, University Boulevard, Stockton-on-Tees, TS17 6BH, UK.
authors.forename: Katharina
authors.initials: K
authors.lastname: Edkins
authors.affiliation: Institut für Anorganische Chemie, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074, Würzburg, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Lorbach
authors.affiliation: Institut für Anorganische Chemie, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074, Würzburg, Germany.|Department of Chemistry, Durham University, South Road, Durham, DH1 3LE, UK.
authors.forename: Andreas
authors.initials: A
authors.lastname: Steffen
authors.affiliation: Institut für Anorganische Chemie, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074, Würzburg, Germany. todd.marder@uni-wuerzburg.de.|Department of Chemistry, Durham University, South Road, Durham, DH1 3LE, UK. todd.marder@uni-wuerzburg.de.
authors.forename: Todd B
authors.identifier: http://orcid.org/0000-0002-9990-0169
authors.initials: TB
authors.lastname: Marder
keywords: OLEDs; dibenzo ligands; intersystem crossing; luminescence; metallacycles; rhodium complexes