Book of Abstracts - Ruhr-Universität Bochum

P-08
ISBOMC `10 5.7 – 9.7. 2010 Ruhr-Universität Bochum
Following Investigations of Antiradical and Bioconjugative Properties of
Cluster Rhenium Compounds
Alexander V. Shtemenko, a Alexander A. Golichenko, a and Nataliia I. Shtemenko b
a Department of Inorganic Chemistry, Ukrainian State Chemical Technological University, Gagarin
Ave. 8, Dnipropetrovs’k 49005, Ukraine., b Department of Biophysics and Biochemistry,
Dnipropetrovs’k National University, 72 Gagarin avenue, Dnipropetrovs’k 49010, Ukraine, E-mail:
shtemenko@ukr.net
Antiradical and bioconjugative properties of the five structural types of cluster dirhenium(III)
compounds with halide, carboxylate and phosphate ligands were described. Antiradical properties of
these substances occurred by δ-component of quadruple Re-Re bond ( �2�� bonds ) and was welldetectable
in electronic absorption spectra (EAS) due to ���* transition (20000 - 14000 cm -1 ). It has
been shown that the binuclear cluster fragment Re2 6+ actively reacts with artificial radicals in vitro,
however the rate of such interaction strongly depended from the ligand environment of the cluster
Re2 6+ -centre. The reaction rate decreased with an increase of induction effects of alkyl groups in the
carboxylic ligands. The mechanism of antiradical action of Re2 6+ -derivatives may be explained by the
transition of an unpaired electron of a synthetic radical to a δ-orbital of the Re2 6+ fragment, thus
decreasing the Re-Re bond order. Cluster rhenium compounds revealed their antiradical properties in
the model of tumor growth. We consider that antiradical properties of the rhenium compounds may
also play a leading role in their antitumor properties. Recent investigations showed that the antiradical
properties of rhenium compounds in vivo depended from the structure of the compounds, but this
dependence did not coincide with that obtained from the investigations with artificial radicals shown
herein and was more complex due to multidirectional interactions in living cells. Presented data
showed positive future prospects for Re2 6+ -substances applications as therapeutic agents due to their
low toxicity and antiradical activity.
Very important was the fact that EAS gave information about the quadruple rhenium - rhenium bond
mode of substitution that was used in the bioconjugative investigations. Different structural types of
Re2 6+ -derivatives had the characteristic absorption maxima, which position were dependent from the
quantity of hyperconjugated cycles around Re2 6+ -centre. The effect of hyperconjugation is realized
due to the interaction of the delocalized �-bond of �-carboxylic ligands group and the �-component
of the Re-Re bond. Bidentate coordinated tetra-�-phosphates [Re2(HPO4)4(H2O)2] 2- and
[Re2(HPO4)2(H2PO4)2(H2O)2] .. 4H2O had the δ→δ* absorption band in the area 15625 см -1 , that
corresponded to the existence of two hyperconjugated cycles around Re2 6+ - centre. These facts were
used by us to show what was happened to the quadruple bond during formation of liposomes and
interactions with lipids. The mechanism of interaction between nucleic bases and rhenium(III)
compounds was studied and another mechanism of the interactions in comparison with platinides was
demonstrated. Some experiments with proteins were also discussed. Thus, quadruple Re-Re bond
offers unique opportunities to study processes of bioconjugation.
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