Pyridine-2 ,6 - Dicarboxylic Acid Derivatives Of Tb (iii) Synthesis And Fluorescence Properties

The complexes of rare earth ions have strong luminescence throughthe energy transfer in the lanthanide complexes with some organicligands, the use of pyridine-2,6-dicarboxylic acid (DPA) derivatives assensitizers was better than using others. Since the lanthanide complexesare chiral, we can get more information about structure of biologicmolecule through measuring Circularly Polarized Luminescence Spectra.The substituted pyridine-2,6-dicarboxylic acid derivatives of Tb (Ⅲ) andEu (Ⅲ) are stabile, luminescence intensities of these complexes arestrong, and lifetime was long. They can be used to tag proteins intime-resolved fluoroimmunoassay (TR-FIA) and applied in the fields offood, iatrology and biology.The two novel ligands named 4-styrylpyridine-2,6-dicarboxylic acid(4-SDPA) and 4-((bis(carboxymethyl)amino)methyl)pyridine-2,6-dicerb-oxylic acid (DBDPA) which have rigid planar structure with excellentelectronic negotiability in theπ-conjugated plane were designed andobtained.Starting from pyridine-2,6-dicarboxylic (1), two novel pyridine-2,6-dicarboxylic acid derivatives were synthesized. Carboxyls were protectedby methoxyl. Through a free radical reaction, hydroxylmethyl was addedin the 4-position of dimethyl pyridine-2,6-dicarboxylate (2). 4-hydroxy-methylpyridine-2,6-dicarboxylic (3) was prepared, and the reactiveconditions of hydroxymethylation was optimized. The hydroxymethyl in4-position of 3 was chloridized by thionyl chloride to produce dimethyl4-(chloromethy-1)pyridine-2,6-dicarboxylate (4), which was reacted withtriphenylphosphine to give dimethyl 4-(methylene) pyridine-2,6-dicarb-oxylate triphenylphosphonium chloride (5). The hydroxymethyl incompound 3 was also oxidized to give dimethyl 4-formylpyridine-2,6-dicarboxylate (8). The compound 5 was reacted with benzaldehyde by theWittig reaction to produce dimethyl ethyl 4-styrylpyridine-2,6-dicerbox-ylate (6) in the alkaline condition, then hydrolyzed, 4-styrylpyr-idine-2,6-dicarboxylic acid (7), which was a novel ligand, was obtained. p-xylene was bromized, then reacted with triphenylphosphine to producep-xylylene bis-(triphenylphosphoniumb romide) (11), which can reactedwith the aldehyde (8) by Wittig reaction to give dimethyl 4-(4-(2,6-dicer-boxylatep-yridin-4-yl)vinyl)styryl)pyridine-2,6-d-icerboxylate (12), thenhydrollyzed, 4-((bis(carboxymethyl)amino)methyl)pyridine-2,6-dicarbo-xylic acid (13), which was another novel multifunctionn nal ligand, wasobtained. All ligands and their intermediates were confirmed by IR,¹HNMR, MS and EA.Furthermore, the following ligands were prepared according to theliterature methods: 4-hydroxypyridine-2,6-dicarboxylic acid (HDPA),4-methoxypyridine-2,6-dicarboxylic acid (MDPA), 4-acetamidopyridine-2,6-dicarboxylic acid (4-ADPA), 4-phenylpyridine-2,6-dicarboxylic acid(BDPA), 4-(hydroxymethyl)pyridine-2,6-dicarboxylic acid (4-HMDPA).The Tb (Ⅲ) complexes of HDPA, DPA, 4-HMDPA, MDPA, BDPA,4-SDPA, 4-ADPA and DBDPA were prepared. The structures ofcomplexes were deduced by EA and IR. The fluorescence properties ofthe solid complexes and their solutions were investigated in detail: thefluorescence of the complexes with electron-donating groups is moreintense than that of the complexes with electron-withdrawing groups in4-position; When the pH value is about at 7, fluorescence intensities ofthe complexes are strongest; while the less the dipole moment of solventmolecule is, the stronger the fluorescence intensity is; The complexNa₆Tb₂(DBDPA)₃·23H₂O, which has a polynuclear polymeric netted str-ucture, has more excellent fluorescence properties, and 4-((bis(carbox-ymethyl)amino)methyl)pyridine-2,6-dicarboxylic acid (DBDPA) are thebest sensitizers for Tb (Ⅲ) ion among the ligands.