Spectroscopic Characterization of the Europium(III) Complexes of a Series of N,N'-bis(carboxymethyl) Macrocyclic Ether Bis(lactones)

Authors

Richard C. Holz, Marquette UniversityFollow
C. Allen Chang, Squibb Institute for Medical Research.
William DeW Horrocks Jr, Pennsylvania State University - Main Campus

Document Type

Article

Publication Date

8-1991

Source Publication

Inorganic Chemistry

Source ISSN

0020-1669

Abstract

The Eu³⁺ and Y³⁺ complexes of a series of N,N'-bis(carboxymethyl) macrocyclic ether bis(lactone) ligands derived from ethylenediaminetetraacetic acid (EDTA) were characterized in solution by using Eu³⁺ laser-induced luminescence and ¹H and ¹³CNMR spectroscopy. The complexation of EDTA was also studied for comparison purposes. These ligands form 1:1 complexes with Eu³⁺ at the concentrations studied (10 µM), with the luminescence lifetimes in H₂O and D₂O providing the number of coordinated water molecules. The ⁷F₀ -> ⁵D₀ excitation spectra indicate that for each of the complexes two isomers are present in fast exchange on the
⁵D₀ time scale. The spectra obtained for the macrocyclic complexes are identical with that of [EuEDTA]^-, suggesting that the ether moieties of the macrocyclic ligands are not involved in direct coordination to the metal ion. These results are corroborated by the ¹H and ¹³CNMR spectra of the Y³⁺ complexes. Changes in the coordination environment of the Eu³+ ion as a function of pH and temperature were observed for each complex. These results suggest that two species, which involve different numbers of coordinated carboxylate moieties, are present in rapid interconversion in solution. The interchange rates between the two species observed in aqueous solution decreases to the slow exchange limit in methanol, allowing each species to be probed independently.

Comments

Inorganic Chemistry, Vol. 30, No. 17 (August 1991): 3270-3275. DOI.

Richard Holz was affiliated with the Pennsylvania State University at the time of publication.

Recommended Citation

Holz, Richard C.; Chang, C. Allen; and Horrocks, William DeW Jr, "Spectroscopic Characterization of the Europium(III) Complexes of a Series of N,N'-bis(carboxymethyl) Macrocyclic Ether Bis(lactones)" (1991). Chemistry Faculty Research and Publications. 298.
https://epublications.marquette.edu/chem_fac/298