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ABSTRACT: The electrochemistry of [Cu(OEP)] and [Ni(OEP)] are compared with the mixed-valence π-cations [Cu(OEP•/2)]2+and[Ni(OEP•/2)]2+. These electrochemical studies, carried out with cyclic voltametry and hydrodynamic voltametry, show that the mixed valence π-cations have distinct electrochemical properties, although the differences between the [M(OEP)](+/0) and [M(OEP•/2)]2+/0 processes are subtle.
Inorganica Chimica Acta 06/2008; 361(6):1722-1727. · 1.85 Impact Factor
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Ulrich Siemeling,
Jens Vor der Brüggen,
Udo Vorfeld,
Beate Neumann,
Anja Stammler,
Hans-George Stammler,
Andreas Brockhinke,
Regina Plessow,
Piero Zanello,
Franco Laschi,
Fabrizia Fabrizi de Biani, Marco Fontani,
Steen Steenken,
Marion Stapper,
Gagik Gurzadyan
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ABSTRACT: Terpyridine ligands of the type Fc'-X-tpy (Fc'=ferrocenyl or octamethylferrocenyl, X=rigid spacer, tpy'=4'-substituted 2,2':6',2''-terpyridine) were prepared, crystallographically characterised and used for the synthesis of di- and trinuclear bis(terpyridine) complexes of RuII, FeII and ZnII. Donor-sensitiser dyads and triads based on RuII were thoroughly investigated by (spectro)electrochemistry, UV/Vis, transient absorption and luminescence spectroscopy, and an energy level scheme was derived on the basis of the data collected. Intramolecular quenching of the photoexcited RuII complexes by the redox-active Fc' groups can occur reductively and by energy transfer. Both the redox potential of the donor Fc' and the nature of the spacer X have a decisive influence on excited-state lifetimes and emission properties of the complexes. Some of the compounds show room-temperature luminescence, which is unprecedented for ferrocenyl-functionalised compounds of this kind.
Chemistry 07/2003; 9(12):2819-33. · 5.93 Impact Factor
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ABSTRACT: The new iridium(III) complex, imidazolium[trans(DMSO,imidazole)tetrachloroiridate(III)], (I) (DMSO=dimethyl sulfoxide), and the orange form of [(DMSO)(2)H][trans(DMSO)(2)tetrachloroiridate(III)], (II) have been prepared and characterized, both in the solid state and in solution, by X-ray diffraction and by various physicochemical techniques. Single crystal X-ray diffraction studies point out that complex (II) is isomorphous to the ruthenium(III) analogue, [(DMSO)(2)H][trans-RuCl(4)(DMSO)(2)], (III). Crystallographic data are the following: a=16.028(2) A, b=24.699(3) A, c=8.262(1) A, in space group Pbca (Z=8) for (imidazolium)[trans(DMSO,imidazole)tetrachloroiridate(III)], (I); and a=9.189(2) A, b=16.511(4) A, c=14.028(3) A, beta=100.82(2) degrees in space group P2/n (Z=4) for [(DMSO)(2)H][trans(DMSO)(2)tetrachloroiridate(III)], (II). Visible absorption spectra show that both complexes are stable for several days, at pH 7.4, at room temperature. No significant chloride hydrolysis is observed, even at high temperature (70 degrees C), over 24 h. The extreme stability of these iridium(III) complexes within a physiological buffer was further assessed by (1)H NMR; in addition, cyclic voltammetry measurements evidenced a high stability of the oxidation state +3. Preliminary biological studies show that both complexes do not bind appreciably bovine serum albumin nor inhibit significantly the proliferation of representative human tumor cell lines, suggesting that hydrolysis of coordinated chlorides is a crucial feature for the biological properties and the antitumor activity of the parent ruthenium(III) complexes.
Journal of Inorganic Biochemistry 06/2003; 95(1):37-46. · 3.35 Impact Factor
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ABSTRACT: Increasing evidence suggests that iron plays an important role in tissue damage both during chronic iron overload diseases (i.e., hemochromatosis) and when, in the absence of actual tissue iron overload, iron is delocalized from specific carriers or intracellular sites (inflammation, neurodegenerative diseases, postischaemic reperfusion, xenobiotic intoxications, etc.). In the present work, we appropriately modified an iron chelator of the hydroxychromene family in order to obtain a tridentate chelator that would inactivate the iron redox cycle after its complexation, with a view to using this molecule in human therapy and/or in disease prevention. We synthesized such a chelator for the first time and show, by different physicochemical analysis, its tridentate nature and, importantly, its capacity to chelate iron with enough strength to inhibit both iron-dependent H(2)O(2) generation and lipid peroxidation in in vitro biological systems.
Journal of Medicinal Chemistry 01/2003; 45(26):5776-85. · 5.25 Impact Factor
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ABSTRACT: Gold(III) complexes generally exhibit interesting cytotoxic and antitumor properties, but until now, their development has been heavily hampered by their poor stability under physiological conditions. To enhance the stability of the gold(III) center, we prepared a number of gold(III) complexes with multidentate ligands − namely [Au(en)2]Cl3, [Au(dien)Cl]Cl2, [Au(cyclam)](ClO4)2Cl, [Au(terpy)Cl]Cl2, and [Au(phen)Cl2]Cl − and analyzed their behavior in solution. The solution properties of these complexes were monitored by visible absorption spectroscopy, mass spectrometry, and chloride-selective potentiometric measurements; the electrochemical properties were also studied by cyclic voltammetry and coulometry. Since all the investigated compounds exhibited sufficient stability under physiological conditions, their cytotoxic properties were tested in vitro, via the sulforhodamine B assay, on the representative human ovarian tumor cell line A2780, either sensitive or resistant to cisplatin. In most cases the investigated compounds showed relevant cell-killing properties with IC50 values falling in the 0.2−10 μM range; noticeably most investigated gold(III) complexes were able to overcome, to a large extent, resistance to cisplatin when tested on the corresponding cisplatin-resistant cell line. The cytotoxic properties of the free ligands were also determined under the same solution conditions. Ethylenediamine, diethylenetriamine, and cyclam were virtually nontoxic (IC50 values > 100 μM) so that the relevant cytotoxic effects observed for [Au(en)2]Cl3 and [Au(dien)Cl]Cl2 could be quite unambiguously ascribed to the presence of the gold(III) center. In contrast the phenanthroline and terpyridine ligands turned out to be even more cytotoxic than the corresponding gold(III) complexes rendering the interpretation of the cytotoxicity profiles of the latter complexes less straightforward. The implications of the present findings for the development of novel gold(III) complexes as possible cytotoxic and antitumor drugs are discussed.
Journal of Medicinal Chemistry 09/2000; 43(19). · 5.25 Impact Factor
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Ulrich Siemeling,
Jens Vor der Brüggen,
Udo Vorfeld,
B.eate Neumann,
Anja Stammler,
Hans-Georg Stammler,
Andreas Brockhinke,
Regina Plessow,
Piero Zanello,
Franco Laschi,
Fabrizia Fabrizi de Biani, Marco Fontani,
Steen Steenken,
Marion Stapper,
Gagik Gurzadyan
Chemistry-A European Journal, v.9, 2819-2833 (2003).
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ABSTRACT: Contradictory results exist in the literature about the antineoplastic activity of ferrocenes and their ferrocenium salts; additionally, little is known about the mechanism by which such drugs become active towards cancer cells. In the present paper we show that only ferrocenium species are able to inhibit the growth of Ehrlich ascites tumor cells in vivo and we propose that the cytotoxic activity of ferrocenium salts is not based on their direct linking to DNA, but on their ability to generate oxygen active species which induce oxidative DNA damage.
Inorganica Chimica Acta.
