| Piperidine-2,6-dicarboxylic acid (PDA), 2,6-dicarboxypiperidine-N-acetic acid (DPA) and chelidamic acid (CA) were characterized using a variety of techniques. The acid dissociation constants of these ligands were determined potentiometric titration and 1H NMR. The crystal structures of PDA and DPA were determined using an X-ray diffractometer.;The stability constants of select trivalent lanthanide ions (La, Nd, Eu, Ho and Lu) with DPA and CA were determined by potentiometric titration. The oscillator strength of the Nd and Ho complexes of DPA and CA were determined by spectroscopic titration. These oscillator strength values were used to examine coordination effects of DPA and CA on Nd(III) and Ho(III). The 7F0 → 5D0 selective excitation was used to examine the inner coordination sphere of the Eu(III) ions upon coordination with DPA and CA. The number of Eu(III) hydrating water molecules and the calculated ligand coordination number were determined for all complex species. The DeltaH and DeltaS of protonation values and DeltaH and DeltaS values of Ho(III) and Nd(III) complexation were determined by calorimetric titration.;The stability constants of PDA could not be determined by potentiometric titration. Oscillator strength measurements, calorimetric titration and laser fluorescence indicated only minimal bonding was occurring between the lanthanide(III) ions and PDA. |
