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Luminescent cyclometalated iridium(III) dipyridoquinoxaline indole complexes as biological probes

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Abstract

Four luminescent cyclometalated iridium(III) dipyridoquinoxaline complexes appended with an indole moiety [Ir(N∧C)2(N∧N)] (PF6) (HN∧C = 2-phenylpyridine, Hppy; N∧N = 2-(N-(2-(indole-3-acetamido)ethyl)aminocarbonyl)dipyrido[3,2-f:2′,3′-h]quinoxaline, dpqC2indole (1a), N∧N = 2-(N-(6-(indole-3-acetamido)hexyl)aminocarbonyl)dipyrido[3,2-f:2′,3′-h]quinoxaline, dpqC6indole (1b); HN∧C = 7,8-benzoquinoline, Hbzq, N∧N = dpqC2indole (2a), N∧N = dpqC6indole (2b)) have been synthesized and characterized. Upon irradiation, all the complexes displayed moderately intense and long-lived luminescence under ambient conditions and in 77 K glass. On the basis of the photophysical data, the emission of the complexes has been assigned to an excited state of triplet metal-to-ligand charge-transfer (3MLCT) ((dπ(Ir) → π*(N∧N)) character. Cyclic voltammetric studies revealed indole-based and iridium-based oxidations at ca. +1.10 V and +1.24 V vs. SCE, respectively, and ligand-based reductions at ca. −1.07 to −2.29 V vs. SCE. The interactions of the complexes with an indole-binding protein, bovine serum albumin (BSA), have been examined by emission titrations.

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  1. Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China

    Kenneth Kam-Wing Lo & Arthur Ho-Hon Leung

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  1. Kenneth Kam-Wing Lo
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Correspondence to Kenneth Kam-Wing Lo.

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Lo, K.KW., Leung, A.HH. Luminescent cyclometalated iridium(III) dipyridoquinoxaline indole complexes as biological probes. Sci. China Chem. 53, 2091–2098 (2010). https://doi.org/10.1007/s11426-010-4120-y

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