TY  - JOUR
A1  - Burek, Katja
A1  - Eidner, Sascha
A1  - Kuke, Stefanie
A1  - Kumke, Michael Uwe
T1  - Intramolecular deactivation processes of electronically excited Lanthanide(III) complexes with organic acids of low molecular weight
JF  - Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy
N2  - The luminescence of Lanthanide(Ill) complexes with different model ligands was studied under direct as well as sensitized excitation conditions. The research was performed in the context of studies dealing with deep-underground storages for high-level nuclear waste. Here, Lanthanide(III) ions served as natural analogues for Actinide(III) ions and the low-molecular weight organic ligands are present in clay minerals and furthermore, they were employed as proxies for building blocks of humic substances, which are important complexing molecules in the natural environment, e.g., in the far field of a repository site. Time-resolved luminescence spectroscopy was applied for a detailed characterization of Eu(III), Tb(III), Sm(III) and.Dy(III) complexes in aqueous solutions. Based on the observed luminescence the ligands were tentatively divided into two groups (A, B). The luminescence of Lanthanide(III) complexes of group A was mainly influenced by an energy transfer to OH-vibrations. Lanthanide(Ill) complexes of group B showed ligand-related luminescence quenching, which was further investigated. To gain more information on the underlying quenching processes of group A and B ligands, measurements at different temperatures (77 K <= T <= 353 K) were performed and activation energies were determined based on an Arrhenius analysis. Moreover, the influence of the ionic strength between 0 M <= 1 <= 4 M on the Lanthanide(III) luminescence was monitored for different complexes, in order to evaluate the influence of specific conditions encountered in host rocks foreseen as potential repository sites.
KW  - Humic substance
KW  - Model ligand
KW  - Metal complexation
KW  - Benzoic acids
KW  - Intramolecular deactivation
Y1  - 2018
U6  - https://doi.org/10.1016/j.saa.2017.09.012
SN  - 1386-1425
VL  - 191
SP  - 36
EP  - 49
PB  - Elsevier
CY  - Oxford
ER  -