Solvent Extraction and Coordination Properties of1,10-Phenanthroline-2,9-dicarboxylic Acid Diamides with Alkyl-ArylSubstituents toward Lanthanides(III) and Americium(III)

For a wide range of 1,10-phenanthroline-2,9-dicarboxylic acid diamides (DAPhen), differing in the structure of the amide substituent and the presence of chlorine atoms in the 4,7-positions of the phenanthroline core, the extraction properties for lanthanides(III) and americium(III) were studied. Protonation and binding constants to Eu(III) were determined by using UV–vis titration. The values of binding constants and protonation constants are higher for nonsubstituted diamides than for 4,7-chlorinated diamides, which is in good agreement with the solvent extraction data. The structures of more than 20 complexes with lanthanide nitrates in the solid state have been determined using X-ray diffraction analysis. Unusual DAPhen ligand complexes with lanthanum and neodymium nitrates were obtained. For the first time, the possibility of entering a water molecule into the internal coordination sphere of neodymium in a complex with the DAPhen ligand was shown, resulting in the coordination number of neodymium increasing to 11. An unusual complex with a bridge structure was obtained for lanthanum nitrate in which the lanthanum ions have different coordination numbers of 10 and 12.