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Issue 35, 2012
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Visible light-harvesting cyclometalated Ir(III) complexes as triplet photosensitizers for triplet–triplet annihilation based upconversion

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Abstract

Visible light-harvesting cyclometalated Ir(III) complexes with 3-(2-benzothiazoly)-7-diethylaminocoumarin as the C^N cyclometalation ligands were prepared. The ancillary N^N ligand is either 6-piperidine naphthalimide-phenanthroline (Ir-1) or 9-aminophenanthroline (Ir-3). Ir(ppy)2(Phen) was prepared as model complex (Ir-2). Ir-1 and Ir-3 show strong absorption of visible light (ε = 109 000 M−1 cm−1 or 112 000 M−1 cm−1 at 486 or 484 nm, respectively). All the complexes show room temperature phosphorescence with drastically different phosphorescence quantum yields (ΦP = 4.3%, 44.3% and 46.0% for Ir-1, Ir-2 and Ir-3, respectively). With steady state and time-resolved spectra, as well as DFT calculations, the T1 excited states of Ir-1 and Ir-3 were proposed to be the 3IL state, whereas the 3MLCT state was proposed for Ir-2. Long-lived emissive triplet excited states (7.6 μs and 54.5 μs) were observed for Ir-1 and Ir-3, compared to the short T1 excited state lifetime of Ir-2 (1.2 μs). The complexes were used as triplet photosensitizers for triplet–triplet annihilation upconversion and upconversion quantum yields (ΦUC) of 19.3% and 12.7% were observed for Ir-1 and Ir-3, respectively. No upconversion was observed for Ir-2 under the same experimental conditions.

Graphical abstract: Visible light-harvesting cyclometalated Ir(iii) complexes as triplet photosensitizers for triplet–triplet annihilation based upconversion

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Publication details

The article was received on 02 May 2012, accepted on 19 Jun 2012 and first published on 19 Jun 2012


Article type: Paper
DOI: 10.1039/C2DT30955F
Citation: Dalton Trans., 2012,41, 10680-10689
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    Visible light-harvesting cyclometalated Ir(III) complexes as triplet photosensitizers for triplet–triplet annihilation based upconversion

    L. Ma, H. Guo, Q. Li, S. Guo and J. Zhao, Dalton Trans., 2012, 41, 10680
    DOI: 10.1039/C2DT30955F

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