Neutral lanthanide complexes based on 5,6′-diaryl-2,2′-bipyridine-6-carboxylic acids: synthesis and photophysical properties

New lanthanide complexes of the composition LnL 3 (Ln = Eu III , Tb III , Dy III , Sm III ) with 5,6′-diaryl-2,2′-bipyridine-6-carboxylate anions, including their cyclopentene-fused analogs, were synthesized. The ligands were prepared using a combination of the “1,2,4-triazine” methodology and the Suzuki cross-coupling reaction. The photophysical properties of the new compounds were investigated. It was found that in some cases, the introduction of an additional phenyl substituent at the C(6′) position of the ligand led to a bathochromic shift of the absorption maxima of the complexes.