A Terpyridine Based 1,2,3‐Triazol‐1,4‐diyl‐Fluoroionophore‐A Fluorometric Study Towards 3d Metal Ions in Acetonitrile

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In this paper, we report on the sensing role of the 1,2,3‐triazol unit in a 1,4‐diyl arrangement in a fully π‐conjugated fluorescent probe 1 (cf. Scheme 1) towards the fluorometric detection of 3d metal ions. The 1,2,3‐triazol‐1,4‐diyl‐fluoroionophore 1 was designed in a donor(D)‐acceptor(A) arrangement with a 1,2,3‐triazol unit as a π‐linker between a terpyridine (A) ionophore and a diethylaminocoumarin (D) fluorophore to study the fluorescence behavior towards the divalent 3d metal ions Mn 2+ , Fe 2+ , Co 2+ , Ni 2+ , Cu 2+ and Zn 2+ . This fluoroionophore 1 is based on an intramolecular charge transfer (ICT) and shows a moderate quantum yield ( φ f ) of 0.508 in acetonitrile. A modulation of the ICT process in 1 through Fe 2+ , Co 2+ , Cu 2+ , Ni 2+ and Zn 2+ leads to a small red shift of the lowest energetically lying absorption UV/Vis absorption band and to a very strong 3d metal ion induced fluorescence quenching. It should be considered, that the installation of a 1,2,3‐triazole unit as a fully π‐linker in ICT probes originates no ratiometric fluorescence response towards Fe 2+ , Co 2+ , Cu 2+ , Ni 2+ and Zn 2+ .