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Issue 18, 2015
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Iridium(III) N-heterocyclic carbene complexes: an experimental and theoretical study of structural, spectroscopic, electrochemical and electrogenerated chemiluminescence properties

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Abstract

Four cationic heteroleptic iridium(III) complexes have been prepared from methyl- or benzyl-substituted chelating imidazolylidene or benzimidazolylidene ligands using a Ag(I) transmetallation protocol. The synthesised iridium(III) complexes were characterised by elemental analysis, 1H and 13C NMR spectroscopy and the molecular structures for three complexes were determined by single crystal X-ray diffraction. A combined theoretical and experimental investigation into the spectroscopic and electrochemical properties of the series was performed in order to gain understanding into the factors influencing photoluminescence and electrochemiluminescence efficiency for these complexes, with the results compared with those of similar NHC complexes of iridium and ruthenium. The N^C coordination mode in these complexes is thought to stabilise thermally accessible non-emissive states relative to the case with analogous complexes with C^C coordinated NHC ligands, resulting in low quantum yields. As a result of this and the instability of the oxidised and reduced forms of the complexes, the electrogenerated chemiluminescence intensities for the compounds are also low, despite favourable energetics. These studies provide valuable insights into the factors that must be considered when designing new NHC-based luminescent complexes.

Graphical abstract: Iridium(iii) N-heterocyclic carbene complexes: an experimental and theoretical study of structural, spectroscopic, electrochemical and electrogenerated chemiluminescence properties

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Publication details

The article was received on 04 Nov 2014, accepted on 04 Feb 2015 and first published on 05 Feb 2015


Article type: Paper
DOI: 10.1039/C4DT03378G
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Dalton Trans., 2015,44, 8564-8576
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    Iridium(III) N-heterocyclic carbene complexes: an experimental and theoretical study of structural, spectroscopic, electrochemical and electrogenerated chemiluminescence properties

    G. J. Barbante, E. H. Doeven, P. S. Francis, B. D. Stringer, C. F. Hogan, P. R. Kheradmand, D. J. D. Wilson and P. J. Barnard, Dalton Trans., 2015, 44, 8564
    DOI: 10.1039/C4DT03378G

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