New chiral pyridine-based Eu(III) complexes: Study of the relationship between the nature of the ligands and the D-5(0) 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 D-5(0) -> F-7(0) 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. (C) 2011 Elsevier B.V. All rights reserved.