Abstract
AbstractFour 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.
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