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

Abstract : Reactions of [Rh((2)-O,O-acac)(PMe3)(2)] (acac=acetylacetonato) and ,-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 (phi=0.07-0.54, =0.2-2.5ns) despite the presence of the heavy metal atom. Rhodium biphenyl complexes (B), which show exceptionally long-lived (hundreds of s) phosphorescence (phi=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 -H-shift. We attribute the different photophysical properties of isomers A and B to a higher excited state density and a less stabilized T-1 state in the biphenyl complexes B, allowing for more efficient intersystem crossing S1Tn and T1S0. 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.
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Chemistry - A European Journal, Wiley-VCH Verlag, 2016, 22 (30), pp.10523-10532. 〈10.1002/chem.201601912〉
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Soumis le : jeudi 14 septembre 2017 - 14:39:46
Dernière modification le : samedi 24 mars 2018 - 01:50:04

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Carolin Sieck, Meng Guan Tay, Marie-Helene Thibault, Robert M. Edkins, Karine Costuas, et al.. Reductive Coupling of Diynes at Rhodium Gives Fluorescent Rhodacyclopentadienes or Phosphorescent Rhodium 2,2'-Biphenyl Complexes. Chemistry - A European Journal, Wiley-VCH Verlag, 2016, 22 (30), pp.10523-10532. 〈10.1002/chem.201601912〉. 〈hal-01395463〉

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