Open AccessModified Calix[4]crowns as Molecular Receptors for Barium
Author(s) -
Steinberg Janine,
Bauer David,
Reissig Falco,
Köckerling Martin,
Pietzsch HansJürgen,
Mamat Constantin
Publication year - 2018
Publication title -
chemistryopen
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.644
H-Index - 29
ISSN - 2191-1363
DOI - 10.1002/open.201800019
Subject(s) - barium , chelation , amide , chemistry , titration , metal , stability constants of complexes , radium , nuclear chemistry , barium sulphate , combinatorial chemistry , radiochemistry , inorganic chemistry , organic chemistry , aqueous solution
A series of modified calix[4]crown‐6 derivatives was synthesized to chelate the heavy group 2 metal barium, which serves as a non‐radioactive surrogate for radium‐223/‐224; radionuclides with promising properties for radiopharmaceutical use. These calixcrowns were functionalized with either cyclic amide moieties or with deprotonizable groups, and the corresponding barium complexes were synthesized. Stability constants of these complexes were measured by using NMR and UV/Vis titration techniques to determine log K values of >4.1. Further extraction studies were performed to characterize the binding affinity of calixcrowns to radioactive barium‐133. Additionally, the ligands containing cyclic amides were investigated regarding their rotational barriers by using temperature‐dependent NMR measurements.