ISBN: 978-83-60043-10-3 - eurobic9

Eurobic9, 2-6 September, 2008, Wrocław, Poland
P148. High-Frequency EPR and Magnetic Studies on a Complex Useful in
Modelling Cu(II) Transport through Biological Membranes
A. Ozarowski a , K. Wojciechowski b M. Brynda c , J. Jezierska d
a
National High Magnetic Field Laboratory, Florida State University, 1800 E. Paul Dirac Drive, Tallahassee,
FL 32310, USA
e-mail: ozarowsk@magnet.fsu.edu
b
Warsaw University of Technology, Department of Analytical Chemistry, Noakowskiego 3, 00-664 Warsaw,
Poland,
c
Department of Chemistry University of California, Davis One Shields Avenue, Davis, CA 95616, USA,
d
Department of Chemistry, Wroclaw University, F. Joliot-Curie 14, Wroclaw 50-383, Poland
Permeation Liquid Membranes (PLM), capable of selective transport of metal ions, are used for biomimetic
purposes to study heavy metal ions speciation. Membranes containing long-chain azacrown ethers and
carboxylic acids transport transition metal ions with the selectivity order Cu(II)> Pb(II) >> Cd(II), and were used
as models of biological membranes of algae [1].
In the course of our mechanistic studies on Cu(II) transport through PLM we have characterized a model of the
active complex formed in membranes during the transport of Cu(II), which is an adduct of dimeric Cu(II)hexanoate
and Cu(II)-1, 10-diaza-18-crown-6 ether complex [2]. The X-Ray structure (Fig. 1) could be only
partially resolved due to high disorder in the carboxylic acid chains. IR, UV/Vis as well as magnetic and highfield
EPR studies presented here support the 1D polymer structure in which Cu-hexanoate dimers alternate with
Cu-azacrown monomers. Exchange integral J of 333 cm -1 (H=JS1S2) was determined from the magnetic
susceptibility measurements.
Magnetic Induction, Tesla
12.0 12.5 13.0 13.5 14.0 14.5
Figure 1. Left: Fragment of the alternating chain of [Cu(C 5H 11COO) 2] 2[Cu(C 12H 26N 2O 4)(C 5H 11COO) 2]. For clarity, all
hydrogen atoms were omitted and only the carboxyl groups of hexanoates are shown.
Right: bottom: EPR spectrum measured at 287K and 412.8 GHz. Asterisks indicate resonances due to the copper-azacrown
complex (g x=2.055 g y=2.066 g z=2.288). Top: Triplet spectrum of the binuclear copper hexanoate simulated with parameters
given in text.
In HF EPR, signals of carboxylato-bridged dimer were observed in addition to the monomeric Cu-azacrown
entities. The spectra indicate that symmetry of the dimer being part of the polymeric chain is higher (axial,
gx=gy=2.072 gz=2.375, D=0.348 cm -1 , E=0) than the symmetry of a separate copper hexanoate dimer (rhombic,
gx=2.050 gy=2.075, gz=2.348, D=0.336cm -1 , E=0.0121cm -1 ). No dimer-monomer exchange interactions were
observed, in agreement with our DFT calculations.
Acknowledgement: This work was supported by the NHMFL. The NHMFL is funded by the NSF through the
Cooperative Agreement No. DMR-0654118 and by the State of Florida. KW acknowledges the financial support
from Warsaw University of Technology.
References:
[1] Zhang, Z.; Buffle, J.; van Leeuwen, H. P.; Wojciechowski, K. Anal. Chem., 78, 5693 (2006)
[2] Wojciechowski, K.; Kucharek, M.; Buffle, J. J. Membr. Sci., 314, 152 (2008)
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