Enhanced EuIII ion luminescence and efficient energy transfer between lanthanide chelates within the polymeric structure in aqueous solutions

Free‐Radical Approach to 4‐Substituted Dipicolinates

“…The resulting nucleophilic carbon-centered radicals were expected, analogously to reports by Minisci, [21] to attack protonated dimethyl dipicolinate (1). Subsequent in situ C-deprotonation of resultant cation-radicals 2 and oxidation of the intermediate radicals 3 with Fe 3+ were intended to yield 4-substituted dipicolinate derivatives of type 4.…”

“…After 16 h the resultant residue of title compound 9 was filtered (2.85 g, 24 %). 1 were added dropwise to a mixture of dimethyl pyridine-2,6-dicarboxylate (2.93 g, 15 mmol), propane-1,3-diol (13 mL, 180 mmol), and H 2 SO 4 (30 % aqueous solution, 20 mL). The reaction mixture was stirred for 15 min after completion of the addition, treated with saturated aq.…”

“…Chromatography with hexane/ethyl acetate (7:3 to 1:1) provided the title compound (0.17 g, 34 %), along with recovered dimethyl pyridine-2,6-dicarboxylate (85 mg, 22 %) and 8a (54 mg, 12 %). 1 The combined extracts were dried and evaporated, and the residue was separated by flash chromatography to yield a mixture of the title compound 9 and unreacted dimethyl pyridine-2,6-dicarboxylate.…”

“…Elementary microanalyses were performed in the Laboratory of Microanalysis of the Hebrew University. Electrospray mass spectra of compounds were recorded on a Finnegan LCQ Classic mass spectrometer in dichloromethane solutions in the presence of 5 % of MeSO 3 H. 1 H NMR spectra were recorded in CDCl 3 on Bruker AMX 300 and DRX 400 NMR spectrometers. Chemical shifts (δ) are measured in ppm using residual solvent peak for calibration.…”

“…Pyridine-2,6-dicarboxylic acid forms nine-coordinating luminescent complexes with lanthanides, providing high quantum yields of phosphorescence [1] and used as luminescent tags, labels, and barcodes. [2] Chiral pybox (2,6-bis-oxazolidinopyridine) ligands, which can be easily prepared from esters or the chloroanhydride of pyridine-2,6-dicarboxylic acid through the use of commercially available chiral amino alcohols, have found numerous applications in transition metal-catalyzed asymmetric syntheses.…”