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Issue 9, 2011
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Photophysical properties of a new series of water soluble iridium bisterpyridine complexes functionalised at the 4′ position

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Abstract

Four new hetero- and homo-leptic iridium(III) bisterpyridine complexes have been prepared which incorporate aniline (tpy-φ-NH2), benzoic acid (tpy-φ-COOH), and benzyl alcohol (tpy-φ-CH2OH) substituents at the 4′ positions of the tpy ligands (tpy = 2,2′:6′,2′′-terpyridine, φ = phenylene). The electrochemical behaviour and ground and excited state spectroscopic properties of the complexes are reported, and the X-ray crystal structures of a homoleptic benzyl alcohol [Ir(tpy-φ-CH2OH)2](PF6)3, homoleptic aniline [Ir(tpy-φ-NH2)2](PF6)3, and heteroleptic benzyl alcohol/aniline substituted complex [Ir(tpy-φ-CH2OH)(tpy-φ-NH2)](PF6)3 have been solved. Complexes with aniline substituents were found to display absorption bands at around 430 nm corresponding to intraligand charge transfer (ILCT) that are sensitive to changes in solvent and pH. Strong emission in the visible region involving the ILCT state is observed in two of the complexes (Φe = 0.7% and 2.6%) in acetonitrile. In the heteroleptic aniline/benzyl alcohol complex the Stokes shift is shown to be linearly related to solvent polarisability according to the Lippert equation, but only for solvents with weak hydrogen bonding interactions. Additionally, in water, emission from the ILCT state is quenched and only weak ligand centred (LC) emission is observed. The long lifetimes and quantum yields of these complexes make them interesting candidates for probes in sensing applications, especially [Ir(tpy-φ-CH2OH)(tpy-φ-NH2)2](PF6)3 due to its unusual sensitivity to the solvent environment.

Graphical abstract: Photophysical properties of a new series of water soluble iridium bisterpyridine complexes functionalised at the 4′ position

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Publication details

The article was received on 01 Oct 2010, accepted on 29 Nov 2010 and first published on 10 Jan 2011


Article type: Paper
DOI: 10.1039/C0DT01317J
Citation: Dalton Trans., 2011,40, 2053-2061
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    Photophysical properties of a new series of water soluble iridium bisterpyridine complexes functionalised at the 4′ position

    D. C. Goldstein, Y. Y. Cheng, T. W. Schmidt, M. Bhadbhade and P. Thordarson, Dalton Trans., 2011, 40, 2053
    DOI: 10.1039/C0DT01317J

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