ISMSC 2007 - Università degli Studi di Pavia

Metal Complexes of the Polyether Ionophore Antibiotic Monensin A :
coordination mode, spectroscopic study, X-ray structures and
antimicrobial activity
PSB 13
Mariana Mitewa 1 , Ivayla N. Pantcheva 1 , Petar Dorkov 1 , Rumyana Zhorova 1 , Boris Shivachev 2 ,
William S. Sheldrick 3
1
Sofia University, Faculty of Chemistry, Department of Analytical Chemistry, 1 J. Bourchier
blvd., 1164 Sofia, Bulgaria
2
Bulgarian Academy of Sciences, Central Laboratory of Mineralogy and Crystallography, Acad.
Georgi Bonchev Str., bl. 107, 1113 Sofia, Bulgaria
3
Lehrstuhl für Analytische Chemie, Ruhr-Universität Bochum, D-44780 Bochum, Germany
Monensin A is a carboxylic polyether ionophore, employed in veterinary medicine for prevention
and treatment of coccidiosis in poultry. It is a lipophylic compound due to the alkyl-rich
backbone and is able to chelate monovalent metal ions thus transporting them across the cell
lipid membranes. The ligand possesses high selectivity toward alkali and Ag + ions, forming
stable neutral complexes by adopting a quasi-cyclic conformation [1-3].
A profound study on the coordination ability of sodium salt of Monensin A (Mon-Na) to bind
divalent metal ions was initiated in order to establish i) if complexation occurs, and ii) if Na + ions,
already bound into the cavity, could be replaced by the corresponding ions introduced
In the present research the complexation of Mon-Na with transition metal ions M 2+ (M = Cu, Co
and Mn) was studied both in solution and in solid phase. The reaction of Mon-Na and
MCl2.nH2O in 1 : 1 ligand-to-metal molar ratio affords the formation of complexes (Mon-
Na)2MCl2.H2O, which were isolated in solid state from acetonitrile-methanol solutions. Copper(I)
complex salt of Mon-Na was obtained as a side product from the reaction of Mon-Na with Cu(II).
The new compounds were studied by various spectroscopic methods (UV-Vis, IR, EPR, FAB-
MS) and elemental analysis; appropriate crystals
were analysed using X-ray diffraction.
The complexes crystallize in monoclinic space group
O6
C2 with a tetrahedrally coordinated transition metal
O4
attached to oxygen atoms of deprotonated carboxyl
O7
O1 Na1
groups of two Mon-Na molecules and to chloride
O11 O8
Cl1 O2
O9
ions (Fig. 1). The sodium ion remains in the cavity of
Cl1
Mn1
the ligand and cannot be replaced by Cu(II), Co(II) or
O2 O11
Mn(II). A preferable octahedral environment around
O9
the transition metal centers is observed in polar
O1 O10
Na1
solvents while the complexes retain their tetrahedral
O4
O8
structure in non-polar media. Copper(I) complex salt
O7
of Mon-Na was obtained as a side product from the
O6
reaction of Mon-Na with Cu(II). The antimicrobial
activity of non-coordinated ligand and its transition
metal complexes was tested against Gram positive
Fig. 1. ORTEP of (Mon-Na) 2MnCl2.H2O Bacillus subtillis ATCC 6633.
[1] W. K. Lutz, F. K. Winkler and J. D. Dunitz, Helv. Chim. Acta, 1971, 54, 1103-1108
[2] D. M. Walba, M. Hermsmeier, R. C. Haltiwanger and J. Hoordik, J. Org. Chem., 1986, 51,
245-247
[3] F. A. A. Raz, P. J. Gates, S. Fowler, A. Gallimore, B. Harvey, N. P. Lopes, C. B. W. Stark, J.
Staunton, J. Klinowski and J. B. Spencer, Acta Cryst., 2003, E59, m1050-m1052
PSB 14
Different Types of Supramolecular Structures Resulting from Synthetic
Procedures
Atsuhisa Miyawaki, Yoshinori Takashima, Hiroyasu Yamaguchi and Akira Harada *
Department of Macromolecular Science, Graduate School of Science, Osaka University,
Toyonaka, Osaka 560-0043 Japan.
E-mail: harada@chem.sci.osaka-u.ac.jp
Assemblies of biomacromolecules formed by noncovalent bonds are ubiquitous in nature.
Much attention has been focused on self-assembled structures and interlocked molecules such
as rotaxanes, catenanes and knots, because of their unique structures and properties. Although
numerous supramolecular structures have been synthesized, to the best of our knowledge there
are no previous examples of cyclodextrin (CD) based self-assembled complexes and
poly[2]rotaxanes consisting of same building blocks.
Previously, we reported preparations and structures of water soluble cyclic tri[2]rotaxanes
(daisy chain necklaces) and linear supramolecular polymers formed by CDs having a cinnamoyl
group and a cinnamamide group as a guest part, respectively [1] . In these supramolecular
systems, substituent moieties were selectively included in CD cavity from its primary or
secondary hydroxyl side as a guest.
Herein, we have prepared the novel supramolecular complexes using the host-guest
interaction of CDs as well as the π-π interaction of the cinnamamide group. p-
Aminocinnamamide-α-CD (1) formed a linear-type pseudo-poly[2]rotaxane in aqueous solutions.
Poly[2]rotaxane (poly1) was prepared by the reaction preorganized pseudo-poly[2]rotaxane
with adamanatane carboxylic acid as a bulky stopper in aqueous solutions (Method 1). It is wellknown
that the adamantyl group is too bulky to thread through the cavity of α-CD. Accordingly,
cinnamamide-α-CD having an adamantyl group (2) did not form pseudo-poly[2]rotaxane
(Method 2), whereas 2 has been found to form novel supramolecular complexes (poly2) as
being different from pseudo-poly[2]rotaxane. The proposed structures of these supramolecular
systems were represented in Figure 1.
Figure 1. Schematic illustration of the supramolecular structures formed by
same building blocks.
[1] (a) Hoshino, T.; Miyauchi, M.; Kawaguchi, Y.; Yamaguchi, H.; Harada, A. J. Am. Chem. Soc.
2000, 122, 9867-9868. (b) Harada, A.; Kawaguchi, Y.; Hoshino, T. J. Incl. Phenom. Macrocycl.
Chem. 2001, 41, 115-121. (c) Miyauchi, M.; Kawaguchi, Y.; Harada, A. J. Incl. Phenom.
Macrocycl. Chem. 2004, 50, 57-62.