New chiral pyridine-based Eu(III) complexes: Study of the relationship between the nature of the ligands and the 5D0 luminescence spectra

In this paper a new family of imines [N,N′-bis(2-pyridylmethylidene)-1,2-(R,S)-cyclohexanediamine (ligand 1); N,N′-bis(2-pyridylmethylidene)-1,2-(R,S)-cyclohexanediamine (ligand 3)] and amines [N,N′-bis(2-pyridylmethylene)-1,2-(R,R + S,S)-cyclohexanediamine (ligand 2); N,N′-bis(2-pyridylmethylene)-1,2-(R,S)-cyclohexanediamine (ligand 4)] pyridine-based chiral ligands and their chiral nitrate Eu(III) complexes is presented. Combination of structural and spectroscopic evidences in the solid state, reveals that the Eu(III) ion environment is characterized by a low symmetry for all the complexes. The 5D0 → 7F0 Eu(III) emission intensity reflects the degree of distortion of the metal surroundings, that is higher in the case of cis isomer of amine-based complex. This new family of Eu(III) chiral complexes are promising candidates for applications in the sensing field as probes in solution of the nitrate anion and of chiral molecules.