Analysis of Anion Binding Effects on the Sensitized Luminescence of Macrocyclic Europium(III) Complexes

Four triazamacrocyclic and two tetraazamacrocyclic ligands carrying two and three coordinating donor groups, respectively, and a carbostyril light‐harvesting antenna were synthesized. The antenna was linked to a macrocycle either via secondary or tertiary amide. Complexation with europium (Eu), gado...

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Bibliographic Details
Published in:Analysis & sensing 2022-11, Vol.2 (6), p.n/a
Main Authors: Kiraev, Salauat R., Weber, Roza R., Wells, Jordann A. L., Orthaber, Andreas, Kovacs, Daniel, Borbas, K. Eszter
Format: Article
Language:English
Subjects:
Anions
cyanide
Emitters
Europium
fluoride
Fluorides
Gadolinium
lanthanide luminescence
Ligands
Luminescence
macrocyclic ligands
NMR
Nuclear magnetic resonance
Oxidation
responsive probes
Terbium
Valence
Water chemistry
Ytterbium
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Summary:Four triazamacrocyclic and two tetraazamacrocyclic ligands carrying two and three coordinating donor groups, respectively, and a carbostyril light‐harvesting antenna were synthesized. The antenna was linked to a macrocycle either via secondary or tertiary amide. Complexation with europium (Eu), gadolinium (Gd), terbium (Tb), and ytterbium (Yb) yielded overall +1 or +2 charged species. Paramagnetic 1H NMR, and steady‐state and time‐resolved luminescence spectroscopies showed that the complexes had 1–3 inner‐sphere water molecules and displayed a variety of coordination geometries in solution. The antennae sensitized Eu(III) and Tb(III) emission with quantum yields of 0.3–4.3 % and 9.9–24.5 %, respectively. The addition of excess fluoride or cyanide to buffered Eu(III) complex solutions resulted in anion‐dependent changes. Fluoride addition increased the Eu(III) luminescence intensity by displacing all inner‐sphere water molecules and stabilizing the +3 oxidation state of Eu. Eu(III) luminescence increased up to 25‐fold for one emitter. Cyanide quenched Eu(III) luminescence in all cases despite partial water ligand displacement. Luminescent Eu(III) and Tb(III) complexes based on variety of macrocyclic ligands were synthesized. Addition of excess fluoride increased Eu(III) emission due to a combination of reduced O−H quenching and better Eu(III) sensitization. Cyanide addition quenched Eu(III) luminescence even when complexes with fewer inner‐sphere water molecules and less O−H quenching were obtained.
ISSN:2629-2742
2629-2742
DOI:10.1002/anse.202200015