Near-infrared photoluminescence of lanthanide complexes containing the hemicyanine chromophore

Three (E)-N-hexadecyl-N′,N′-dimethylamino-stilbazolium tetrakis(1-phenyl-3-methyl-4-benzoyl-5-pyrazolonato) lanthanide(III) complexes, containing trivalent neodymium, erbium and ytterbium, show near-infrared luminescence in acetonitrile solution upon UV irradiation. Because of the absence of an α-hydrogen atom in the pyrazolonato ligands, and because of the saturation of the coordination sphere by four bidentate ligands, the luminescence properties are enhanced when compared to, e.g. quinolinate complexes.