Luminescent Iridium(III) Complexes Supported by N-Heterocyclic Carbene-based C^C^C-Pincer Ligands and Aromatic Diimines

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journal

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Author(s)

  • Lai-Hon Chung
  • Dik-Lung Ma
  • Chung-Hang Leung

Detail(s)

Original languageEnglish
Article number15394
Journal / PublicationScientific Reports
Volume5
Publication statusPublished - 21 Oct 2015

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Abstract

Iridium(III) hydrido complexes containing N-heterocyclic carbene (NHC)-based pincer ligand 1,3-bis(1-butylimidazolin-2-ylidene)phenyl anion (C1^C^C1) or 1,3-bis(3-butylbenzimidazolin-2-ylidene) phenyl anion (C2^C^C2) and aromatic diimine (2,2'-bipyridine (bpy), 1,10-phenanthroline (phen), 4,4'-dimethyl-2,2'-bipyridine (Me2bpy), or dipyrido-[3,2-f:2',3'-h]-quinoxaline (dpq)) in the form of [Ir(C^C^C)(N^N)(H)]+ have been prepared. Crystal structures for these complexes show that the Ir-CNHC distances are 2.043(5)-2.056(5) Å. The hydride chemical shifts for complexes bearing C1^C^C1 (-20.6 to-20.3 ppm) are more upfield than those with C2^C^C2 (-19.5 and-19.2 ppm), revealing that C1^C^C1 is a better electron donor than C2^C^C2. Spectroscopic comparisons and timedependent density functional theory (TD-DFT) calculations suggest that the lowest-energy electronic transition associated with these complexes (λ = 340-530 nm (∈ ≤ 103 dm3 mol-1 cm-1)) originate from a dπ(IrIII) → π∗(N^N) metal-to-ligand charge transfer transition, where the dp(IrIII) level contain significant contribution from the C^C^C ligands. All these complexes are emissive in the yellowspectral region (553-604 nm in CH3CN and CH2Cl2) upon photo-excitation with quantum yields of 10-3-10-1.

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