Spectroscopic Characterization of Some Rare Earth Complexes of Triethylenetetraaminehexaacetic Acid
Inorganica Chimica Acta
The Eu3+ complexes formed with triethylenetetraaminehexaacetic acid (TTHA) were characterized in solution by laser-induced Eu3+ luminescence spectroscopy. Both 2:1 and 1:1 metal:ligand complexes were detected at pH 6.0 depending on the metal- ligand stoichiometry. These two species exhibit distinct excited-state lifetimes of 260 and 1210 μs, respectively. The 2:1 complex coordinates three or four water molecules at each Eu3+ ion while the 1:1 complex has no coordinated water molecules. The 7F0→5D0 excitation spectra revealed multiple isomeric forms for both the 2:1 and 1:1 complexes. Spectra and excited-state lifetimes were taken as a function of pH for a 1:1 metal:ligand solution. As the pH increases, an equilibrium shift from the 2:1 species to the 1:1 species occurs. 1H and 13C spectra of the diamagnetic La3+, Y3+ and Lu3+ complexes were recorded. The La3+ chelate of TTHA exhibits long- lived nitrogen and short-lived oxygen bonds, on the NMR time scale, while the Y3+ and Lu3+ adducts spectra are complicated due to fluctional processes.
Holz, Richard C. and Horrocks, William DeW Jr, "Spectroscopic Characterization of Some Rare Earth Complexes of Triethylenetetraaminehexaacetic Acid" (1990). Chemistry Faculty Research and Publications. 345.