New Eu(III)-based complex with a C1 symmetric chiral ligand: A spectroscopic study

The synthesis of the new chiral ligand N, N'-bis[(2-quinolylmethyl]-cyclohexanediamine-N-tert-butylacetate N'-acetic acid and its Eu complex is presented. The spectroscopic investigation of the complex has been performed both in the solid state and in solution of ethanol. Thanks to the heteroaromatic quinoline ring, an efficient ligand to europium energy transfer (antenna effect) is possible. The low symmetry of the ligand (C-1 point symmetry) guarantees a strongly distorted Eu(III) geometric environment and the predominance of the D-5(0)-> F-7(2) hypersensitive band, in the Eu(III) luminescence emission spectrum. As for the majority of the Eu(III)-based coordination compounds, the observed lifetime of the D-5(0) excited state of the complex under investigation falls in the range of ms. Further, its good solubility in polar protic solvent (ethanol) and the excitation around 320 nm, which minimizes interfering excitation of chromophores in biological media, candidates this molecule for applications in the biomedical field.