Highly luminescent, water-soluble lanthanide fluorobenzoates : syntheses, structures and photophysics, part I : lanthanide pentafluorobenzoates

Highly luminescent, photostable, and soluble lanthanide pentafluorobenzoates have been synthesized and thoroughly characterized, with a focus on Eu-III and Tb-III complexes as visible emitters and Nd-III, Er-III, and Yb-III complexes as infrared emitters. Investigation of the crystal structures of the complexes in powder form and as single crystals by using X-ray diffraction revealed five different structural types, including monomeric, dimeric, and polymeric. The local structure in different solutions was studied by using X-ray absorption spectroscopy. The photoluminescence quantum yields (PLQYs) of terbium and europium complexes were 39 and 15%, respectively; the latter value was increased almost twice by using the heterometallic complex [Tb0.5Eu0.5(pfb)(3)(H2O)] (Hpfb=pentafluorobenzoic acid). Due to the effectively utilized sensitization strategy (pfb)(-)-> Tb -> Eu, a pure europium luminescence with a PLQY of 29% was achieved