Abstract
The synthesis, structural characterization and biological activity of eight
ortho-quinone(
N-aryl)-oximine rhenium(
i) complexes are described. The reaction of the halogenido complexes (CO)
5ReX (X=Cl (
4), Br (
5)) with 2-nitroso-
N-arylanilines {(C
6H
3ClNO)NH(C
6H
4R)} (R
=
p-Cl,
p-Me,
o-Cl, H) (
3a–
d) in tetrahydrofurane (THF) yields the complexes
fac-(CO)
3XRe{(C
6H
3ClNO)NH(C
6H
4R)} (
6a–
d,
7a–
d) with the tautomerized ligand acting as a
N,
N′-chelate. The substitution of two carbonyl ligands leads to the formation of a nearly planar 5-membered metallacycle. During coordination the amino-proton is shifted to the oxygen of the nitroso group which can be observed in solution for
6 and
7 by
1H NMR spectroscopy and in solid state by crystal structure analysis. After purification, all compounds have been fully characterized by their
1H and
13C NMR, IR, UV/visible (UV/Vis) and mass spectra. The X-ray structure analyses revealed a distorted octahedral coordination of the CO, X and
N,
N′-chelating ligands for all Re(
i) complexes. Biological activity of four oximine rhenium(
i) complexes was assessed
in vitro in two highly aggressive cancer cell lines: human metastatic melanoma A375 and human chronic myelogenous leukemia K562. Chlorido complexes (
6a and
6c) were more efficient than bromido compounds (
7d and
7b) in inducing apoptotic cell death of both types of cancer cells. Melanoma cells were more susceptible to tested rhenium(
i) complexes than leukemia cells. None of the ligands (
3a–
d) showed any significant anticancer activity.
From nitroso to oximine: First
ortho-quinoid oximine complexes have been synthesized and fully characterized by
1
H and
13C NMR, IR, UV/visible and mass spectra and X-ray structure analysis. They were generated by tautomerization of 2-nitroso-
N-arylanilines in the coordination sphere of rhenium(
i) and show significant
in vitro anticancer activity.
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