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Electrospray ionization mass spectrometric investigations of the complexation behavior of macrocyclic thiacrown ethers with bivalent transitional metals (Cu, Co, Ni and Zn)
Author(s) -
Tsybizova Alexandra,
Tarábek Ján,
Buchta Michal,
Holý Petr,
Schröder Detlef
Publication year - 2012
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.6352
Subject(s) - chemistry , electron paramagnetic resonance , electrospray ionization , copper , mass spectrometry , metal , metal ions in aqueous solution , inorganic chemistry , analytical chemistry (journal) , transition metal , ion , stability constants of complexes , organic chemistry , chromatography , nuclear magnetic resonance , catalysis , physics
RATIONALE Heavy metals are both a problem for the environment and an important resource for industry. Their selective extraction by means of organic ligands therefore is an attractive topic. The coordination of three thiacrown ethers to late 3d‐metal ions was investigated by a combination of electrospray ionization mass spectrometry (ESI‐MS) and electron paramagnetic resonance (EPR). METHODS The mass spectrometric experiments were carried out in an ion trap mass spectrometer with an ESI source. Absolute binding constants were estimated by comparison with data for 18‐crown‐6/Na + . EPR spectroscopy was used as a complementary method for investigating the Cu I /Cu II redox couple. RESULTS The study found that thiacrown ethers preferentially bind traces of copper even at an excess of other metal ions (Co II , Ni II , and Zn II ). The absolute association constants of the Cu I complexes were about 10 8 M –1 , and about two orders of magnitude lower for the other 3d‐metal cations. The EPR spectra demonstrated that the reduction from Cu II to Cu I upon formation of the [(thiacrown)Cu] + species takes place in solution. CONCLUSIONS ESI‐MS demonstrated that the three thiacrown ligands examined had high binding constants as well as good selectivities for copper(I) at low concentrations, and in the presence of other metal ions. By a combination of ESI‐MS and EPR spectrometry it was shown that the reduction from Cu II to Cu I occurred in solution. Copyright © 2012 John Wiley & Sons, Ltd.