| Pyridine-2,6-dicarboxylic is the best sensitizer of the lanthanide (Tb~3+, Eu~3+) than salicylic , phenanthroline. And the lanthanide complexes of pyridine-2,6-dicarboxylic are chiral complexes. Because of that we can obtain much information from measuring Circularly Polarized Luminescence Spectra and see the local structure of biologic molecules.To find better sensitizers of lanthanide ion the design of ligand is the key strategy. The functional groups which are placed at 4-position of pyridine-2,6-dicarboxylic acid can effect the electron cloud of the lanthanide complexes. However, the fluorescence intensities and lifetimes of the complex are related with the energy transfer.Iminodiacetic acid is wildly used in preparing the the lanthanide complexes. The replace group-bis(carboxymethyl)amino) can reform the coordination capacity and ligancy of ligands. And it can form two chelating rings to chelated the other lanthanide ion, the complexes would be net molecules and chiral. The iminodiacetic derivatives are wildly studied in the fluorescence analysis field of biologic molecules.Starting from pyridine-2,6-dicarboxylic (1), a series of novel pyridine-2,6-dicarboxylic acid derivatives were synthesized. Carboxyls were protected by methoxyl. Through a free radical reaction, hydroxymethyl was added in the 4-position of pyridine-2,6-dicarboxylic. 4-hydroxymethylpyridine-2,6-dicarboxylic(3) was prepared. Because that hydroxyl was a reactive group and tosyloxyl(TsO) was an easy-off group, the hydroxyl reacted with TsCl to produce sulfonic ester: dimethyl 4-((tosyloxy)methyl)pyridine-2,6-dicarboxylate (6). Tosyloxyl was replaced by iodine ion and dimethyl 4-(iodomethyl)pyridine-2, 6-dicarboxylate was produced (7). At last iodine ion was replaced by bis(carboxymethyl)amino, dimethyl 4-((bis(carboxymethyl)amino)methyl) pyridine-2,6-dicarboxylate was obtained (8), and through hydrolyzing 4-((bis(carboxymethyl)amino)methyl) pyridine-2,6-dicarboxylate (9), which is a novel multifunctional ligand, was obtained. Furthermore4-hydroxymethylpyridine-2,6-dicarboxamide (4) and 4-hydroxymethyl pyridine-2,6-dicarboxylic (5) were synthesized.Compound 3, 4, 5, 6, 7, 8 and 9 were not reported by references. The structures of the compounds were deduced by the 'H and I3C nuclear magnetic resonance (NMR), elemental analysis (EA), infrared (IR) and mass spectrum (MS).The Tb (III) and Eu (III) complexes with pyridine-2,6-dicarboxylate, 4-(hydroxymethyl)pyridine-2,6-dicarboxylate and 4-((bis(carboxymethyl) amino)methyl) pyridine-2,6-dicarboxylate were prepared. The structures of these complexes were deduced by EA and IR. The fluorescence properties of the solid complexes and their solutions were investigated in detail. The results indicate that the weak election-withdrawing group hydroxymethyl in 4-position of pyridine in 4-(hydroxymethyl) pyridine-2,6-dicarboxylate can weaken the fluorescence intensity of the lanthanide complexes; The contradistinctive experimental results show that the fluorescence intensities of these complexes are related to pH value of aqueous solution and the dipole moment of solution molecule: in the neutral aqueous solution, the fluorescence intensities of these complexes are strongest, while the less the dipole moment is, the stronger the fluorescence intensity is. 4-((bis(carboxymethyl)amino)methyl) pyridine-2,6-dicarboxylate is the better sensitizer and may be used as time-resolved fluorommunoassay. |
