Luminescent Lanthanide Complexes with Fluorinated Heterocycles as Light‐Harvesting Antennae

Abstract Luminescent lanthanide complexes with two types of macrocyclic metal binding sites (tetraazacyclododecane‐1,4,7‐triacetic acid (do3a) and 1,4,7‐triazacyclononane (tacn)) were synthesized. The complexes carry fluorine‐ or trifluoromethyl‐substituted carbostyril heterocycles as light‐harvesting antennae; the key 7‐amino‐3‐trifluoromethylcarbostyril and 7‐amino‐4‐fluorocarbostyril building blocks were accessed from simple starting materials. Lanthanide complexes were characterized by paramagnetic 1 H NMR spectroscopy (Eu(III) complexes), and UV‐Vis absorption and emission spectroscopy. Antenna models were also studied with cyclic voltammetry. The position of the F/CF 3 ‐substitution had a significant impact on the emission properties of the complexes. Further emitter optimization was possible by varying the macrocycle structure and the linker between the macrocycle and the antenna. The most emissive Tb(III) complex was based on a do3a framework linked via a secondary amide to a 7‐amino‐4‐fluorocarbostyril antenna (43 % luminescence quantum yield), for Eu(III) the highest quantum yield (13 %) was obtained with a 7‐amino‐4‐trifluoromethylcarbostyril antenna attached to a tacn macrocycle via a tertiary amide. Dy(III) and Sm(III) luminescence was also sensitized by the new antennae. The quantum yields of the Sm(III) emitters were similar irrespective of substitution pattern, while those of the Dy(III) complexes varied by 10‐fold.