A europium complex with enhanced long-wavelength sensitized luminescent properties

We report a new complex Eu(tta)(3).bpt (tta = thenoyltrifluoroacetonate; bpt = 2-(N,N-di-ethylanilin-4-yl)-4,6-bis(pyrazol-1-yl)-1,3,5-triazine) with excellent long-wavelength sensitized luminescent properties, in which four hydrogen atoms replace the methyl groups at the 3,3'- and 5,5'-positions of the pyrazolyl rings in a previously reported complex Eu(tta)(3).dpbt. Upon visible-light excitation (lambda(ex) = 410 nm) at 295 K, the quantum yield (Phi(Ln)(L)) of Eu(3+) luminescence of Eu(tta)(3).bpt is higher by 23% than that of Eu(tta)(3).dpbt. Different from the case of Eu(tta)(3).dpbt, Phi(Ln)(L) of Eu(tta)(3).bpt increases linearly with the decrease in temperature. Because of the different coordination environments around Eu(3+) ion, the fine structure of the hypersensitive (5)D(0)-->(7)F(2) emission band of Eu(tta)(3).bpt is quite different from that of Eu(tta)(3).dpbt, with the strongest emission line locating at 620 nm rather than 613 nm where the strongest emission line of Eu(tta)(3).dpbt appears. The excitation window of Eu(tta)(3).bpt is much broader than that of Eu(tta)(3).dpbt with a red edge extending up to 450 nm in a dilute toluene solution (1.0 x 10(-5) M) and 500 nm in a toluene solution (1.0 x 10(-2) M). Eu(tta)(3).bpt also exhibits excellent two-photon-excitation luminescent properties.