Spectroscopic Characterization of the 3+ and 2+ Oxidation States of Europium in a Macrocyclic Tetraglycinate Complex
Recommended Citation
Ekanger LA, Mills DR, Ali MM, Polin LA, Shen Y, Haacke EM, and Allen MJ. Spectroscopic characterization of the 3+ and 2+ oxidation states of europium in a macrocyclic tetraglycinate complex. Inorg Chem 2016; 55(20):9981-9988.
Document Type
Article
Publication Date
10-17-2016
Publication Title
Inorganic chemistry
Abstract
The 3+ and 2+ oxidation states of europium have drastically different magnetic and spectroscopic properties. Electrochemical measurements are often used to probe EuIII/II oxidation state changes, but a full suite of spectroscopic characterization is necessary to demonstrate conversion between these two oxidation states in solution. Here, we report the facile conversion of an europium(III) tetraglycinate complex into its EuII analogue. We present electrochemical, luminescence, electron paramagnetic resonance, UV-visible, and NMR spectroscopic data demonstrating complete reversibility from the reduction and oxidation of the 3+ and 2+ oxidation states, respectively. The EuII-containing analogue has kinetic stability within the range of clinically approved GdIII-containing complexes using an acid-catalyzed dissociation experiment. Additionally, we demonstrate that the 3+ and 2+ oxidation states provide redox-responsive behavior through chemical-exchange saturation transfer or proton relaxation, respectively. These results will be applicable to a wide range of redox-responsive contrast agents and Eu-containing complexes.
PubMed ID
27244124
Volume
55
Issue
20
First Page
9981
Last Page
9988
