Antitumor pentamethylcyclopentadienyl rhodium complexes of maltol and allomaltol

Author(s)
Orsolya Doemoetoer, Sabine Aicher, Melanie Schmidlehner, Maria S. Novak, Alexander Roller, Michael A. Jakupec, Wolfgang Kandioller, Christian G. Hartinger, Bernhard K. Keppler, Eva A. Enyedy
Abstract

The reaction of the dimer [Rh

III(pentamethylcyclopentadienyl) (μ-Cl)Cl]

2 ([Rh

III(Cp*)(μ-Cl)Cl]

2) with the hydroxypyrone ligands maltol and allomaltol affords complexes of the general formula [Rh

III(Cp*)(L)Cl] under standard and microwave conditions. The organometallic compounds were characterized by standard analytical methods and in the case of the allomaltol derivative in the solid state by single-crystal X-ray diffraction analysis. The complexes showed similar cytotoxicity profiles and were proved to be moderately active against various human cancer cell lines. The stoichiometry and stability of these complexes were determined in aqueous solution by pH-potentiometry,

1H NMR spectroscopy and UV-visible spectrophotometry. Speciation was studied in the presence and in the absence of chloride ions. Hydrolysis of [Rh

III(Cp*)(H

2O)

3]

2 + gave dimeric mixed hydroxido species [(Rh

III(Cp*))

2(μ-OH)

3]

+ and [(Rh

III(Cp*) )

2(μ-OH)

2Z

2] (Z = H

2O/Cl

-). Formation of the mononuclear complexes [Rh

III(Cp*)(L)Z] of maltol and allomaltol with similar and moderate stability was found. These species predominate at physiological pH and decompose only partially at micromolar concentrations. In addition, hydrolysis of the aqua complex or a chlorido/hydroxido co-ligand exchange resulted in the formation of the mixed-hydroxido species [Rh

III(Cp*)(L)(OH)] in the basic pH range. Replacement of the chlorido by an aqua ligand in the complex [Rh

III(Cp*)(L)Cl] was monitored and with the help of the equilibrium constants the extent of aquation at various chloride concentrations of the extra- and intracellular milieu can be predicted. Complexation of these Rh

III complexes was compared to analogous [Ru

II(η

6-p-cymene)] species and higher conditional stabilities were found in the case of the Rh

III compounds at pH 7.4.

Organisation(s)
Department of Inorganic Chemistry
External organisation(s)
University of Szeged, University of Auckland
Journal
Journal of Inorganic Biochemistry
Volume
134
Pages
57-65
No. of pages
9
ISSN
0162-0134
DOI
https://doi.org/10.1016/j.jinorgbio.2014.01.020
Publication date
05-2014
Peer reviewed
Yes
Austrian Fields of Science 2012
104003 Inorganic chemistry, 106002 Biochemistry, 106023 Molecular biology
Keywords
ASJC Scopus subject areas
Biochemistry, Inorganic Chemistry
Sustainable Development Goals
SDG 3 - Good Health and Well-being
Portal url
https://ucrisportal.univie.ac.at/en/publications/6ad2cc5c-fef6-479f-a339-dbb4579f409c