Luminescence properties of the co-luminescence groups of Sm-La-pyridyl carboxylic acids

A novel ligand, N,N′-(2,6–pyridinedicarbonyl)bis[N-(carboxymethyl)] (L1) was designed and synthesized starting from pyridine–2,6-dicarboxylic acid (1). The ligand (L1) and intermediate product (3) were characterized by 1H nuclear magnetic resonance (NMR), Fourier transform infrared spectrometer (FT–IR) spectra and elemental analysis. Besides, four novel co-luminescence systems of Sm-La-pyridyl carboxylic acids: K4Sm(1-x)Lax(L1)Cl3·y1H2O, K12Sm2(1-x)La2x(L2)3 Cl6·y2H2O, K6Sm2(1-x)La2x(L3)Cl6·y3H2O and K4Sm(1-x)Lax(L4)Cl3·y4H2O (x was the mole fraction of La(III) in the mixed ions, the value was 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, respectively; y1, y2, y3, y4 were plus integer) were studied, and the mechanism of fluorescence enhancement effect was discussed detailedly.