Thermally induced defluorination during a mer to fac transformation of a blue-green phosphorescent cyclometalated iridium(III) complex

Yonghao Zheng, Andrei S. Batsanov, Robert M. Edkins, Andrew Beeby, Martin R. Bryce

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55 Citations (Scopus)

Abstract

The new homoleptic tris-cyclometalated [Ir(C λN) 3] complexes mer-8, fac-8, and fac-9 incorporating γ-carboline ligands are reported. Reaction of 3-(2,4-difluorophenyl)-5-(2-ethylhexyl)- pyrido[4,3-b]indole 6 with iridium(III) chloride under standard cyclometalating conditions gave the homoleptic complex mer-8 in 63% yield. The X-ray crystal structure of mer-8 is described. The Ir-C and Ir-N bonds show the expected bond length alternations for the differing trans influence of phenyl and pyridyl ligands. mer-8 quantitatively isomerized to fac-8 upon irradiation with UV light. However, heating mer-8 at 290 °C in glycerol led to an unusual regioselective loss of one fluorine atom from each of the ligands, yielding fac-9 in 58% yield. fac-8 is thermally very stable: no decomposition was observed when fac-8 was heated in glycerol at 290 °C for 48 h. The γ-carboline system of fac-8 enhances thermal stability compared to the pyridyl analogue fac-Ir(46dfppy) 310, which decomposes extensively upon being heated in glycerol at 290 °C for 2 h. Complexes mer-8, fac-8, and fac-9 are emitters of blue-green light (λ max em = 477, 476, and 494 nm, respectively). The triplet lifetimes for fac-8 and fac-9 are ∼4.5 μs at room temperature; solution φ PL values are 0.31 and 0.22, respectively.

Original languageEnglish
Pages (from-to)290-297
Number of pages8
JournalInorganic Chemistry
Volume51
Issue number1
DOIs
Publication statusPublished - 2 Jan 2012

Keywords

  • defluorination
  • phosphorescence
  • iridium(III) chloride

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