Fluorenylporphyrins functionalized by electrochromic ruthenium units as redox-triggered fluorescence switches

Two dyads containing tris- and tetrakis-meso -fluorenyl-substituted porphyrin and ethynylruthenium units, 1 and 2 , were investigated by emission spectro-electrochemical (SEC) methods for their potential use as fluorescence switches. The ruthenium group as a potential electron donor and the porphyri...

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Published in:Dalton transactions : an international journal of inorganic chemistry 2019-08, Vol.48 (31), p.11897-11911
Main Authors: Zhang, Xu, Abid, Seifallah, Shi, Limiao, Williams, J. A. Gareth, Fox, Mark A, Miomandre, Fabien, Tourbillon, Clarisse, Audibert, Jean-Frédéric, Mongin, Olivier, Paul, Frédéric, Paul-Roth, Christine O
Format: Article
Language:English
Subjects:
Chemical Sciences
Electrochromism
Emission analysis
Fluorescence
Near infrared radiation
Oxidation
Porphyrins
Ruthenium
Switches
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Summary:Two dyads containing tris- and tetrakis-meso -fluorenyl-substituted porphyrin and ethynylruthenium units, 1 and 2 , were investigated by emission spectro-electrochemical (SEC) methods for their potential use as fluorescence switches. The ruthenium group as a potential electron donor and the porphyrin as a potential electron acceptor are connected by a phenylene bridge in 1 and by a fluorenylene bridge in 2 . The new fluorenyl-linked dyad 2 was probed by UV-visible, near-infrared (NIR) and infrared (IR) absorption SEC methods, and the properties interpreted with the aid of hybrid-DFT computations, for comparison with reported data for 1 . The porphyrin-based fluorescence of 1 decreased in intensity upon oxidation to 1 + and decreased further on oxidising 1 + to 1 2+ . A much weaker change in the fluorescence intensity of 2 was observed upon oxidation to 2 + but the intensity decreased upon subsequent oxidation of 2 + to 2 2+ . These findings contrast with data reported for some other porphyrins appended with redox-active ruthenium or iron units, where fluorescence intensities increase upon oxidation of the peripheral metal centers, but they match data reported more recently for closely related arrays. A rationale for these apparently contrasting observations is proposed. The electrofluorochromic behaviour of two ruthenium-appended porphyrin dyads has been investigated. Differences in response according to the nature of the interposed aryl linker are rationalised with the aid of electrochemistry and TD-DFT calculations.
ISSN:1477-9226
1477-9234
DOI:10.1039/c9dt02087j