Synthesis and characterization of new phosphoramide ligands for the preparation of luminescent manganese and f-block metal complexes

Abstract

New luminescent Ln(III) and Mn(II) complexes were prepared and their optical properties were investigated. The experimental work first concerned the synthesis of new neutral phosphoramide ligands, designed and studied in order to improve the efficiency of light absorption and ligand-to-metal energy transfer. Red emitting Eu(III) and green emitting Tb(III) nitrate complexes with phosphoramide ligands were synthetized, together with analogous Gd(III) derivatives in order to obtain information about the excited states of the ligands. The formal replacement of nitrate ions with beta-diketonate ligands such as dbm (dibenzoylmethanate) and tta (tenoyltrifluoroacetonate) afforded strong red-emitting species with general formulae Eu(β-dike)3L and Eu(β-dike)3L2. The same phosphoramide ligands allowed the isolation of Mn(II) halide complexes, showing green, yellow or red emissions depending upon the coordination number. The complexes and the ligands were characterized by UV-vis spectroscopy, IR, NMR and magnetism measurements, while the optical properties were investigated by PL, PLE, and life time measurements. The stability of the obtained complexes in polymer matrices was finally investigated.