Highly‐Luminescent DTTA‐Appended Water‐Soluble Lanthanide Complexes of 4‐(Het)aryl‐2,2′‐bipyridines: Synthesis and Photophysical Properties

New series of highly luminescent DTTA (DTTA=diethylenetriaminetetraacetic acid) ‐ appended water‐soluble lanthanide complexes of 4‐(het)aryl‐2,2′‐bipyridines were prepared. By using the Kröhnke method and the alkylation reaction sequence, the corresponding 4‐(het)aryl‐2,2′‐bipyridines were synthesized in good yields, and their Eu(III), Tb(III), Dy(III) and Sm(III) complexes were prepared. Photophysical properties were studied for all the obtained complexes and the influence of the nature of the (het)aromatic substituent of 2,2′‐bipyridine moiety on the photoluminescence of the resulted lanthanide complexes was investigated. An efficient sensitization of lanthanide luminescence by halogen‐ and methoxyphenyl‐substituted 2,2′‐bipyridine ligands were observed to result in up to 56% and up to 25% quantum yields for Tb(III) and Eu(III) luminescence accordingly.