High-pressure proton NMR study of acetonitrile exchange kinetics on [Rh2(CH3CN)10]4+ and 17O NMR investigation of aqueous solutions of [Rh2(H2O)10]4 +

Pittet, Pierre-André; Dadci, Lynda; Zbinden, Pascal; Abou-Hamdan, Amira; Merbach, André E.

doi:10.1016/s0020-1693(00)82859-5

Cited by 20 publications

(8 citation statements)

References 30 publications

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“…This spectrum is invariant over the course of 7 days. The breadth of the resonance at δ = 2.42 indicates that rapid exchange is occurring at the axial sites . The lability of the axial positions is so high, in fact, that axial exchange reactions of [Rh 2 (MeCN) 10 ] 4+ occur even in the solid state, as evidenced by the color changes of suspensions of [Rh 2 (MeCN) 10 ][BF 4 ] 4 in MeOH (red), THF (pale orange), or acetone (olive green).…”

Section: Resultsmentioning

confidence: 99%

A Remarkable Family of Rhodium Acetonitrile Compounds Spanning Three Oxidation States and with Nuclearities Ranging from Mononuclear and Dinuclear to One-Dimensional Chains

et al. 1999

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A series of homoleptic cations of Rh(I,II), Rh(II), and Rh(III) have been synthesized and characterized in the solid-state and in solution. Three new dinuclear compounds of dirhodium(II,II) were prepared by treatment of Rh2(O2CCH3)4(L)2 with Et3OBF4 or Me3Si(CF3SO3) in acetonitrile or propionitrile. The cations in [Rh2 II,II(MeCN)10][BF4]4 (1), [Rh2 II,II(MeCN)10][SO3CF3]4 (2), and [Rh2 II,II(EtCN)10][BF4]4 (3) contain eight equatorial RCN groups oriented in an approximately square planar arrangement around the two Rh atoms and two axial RCN molecules. The redox properties of 1−3 were investigated by cyclic voltammetry, which revealed the presence of one or two irreversible reduction(s) but no oxidations. Although there was no electrochemical evidence for an accessible oxidation, it was found that treatment of [Rh2 II,II(MeCN)10][BF4]4 with NOBF4 occurs to yield another member of the homoleptic acetonitrile family, namely, the octahedral d6 cation [RhIII(MeCN)6][BF4]3, (4). The corresponding one-electron reduction product was isolated by a slow galvanostatic reduction of [Rh2 II,II(MeCN)10][BF4]4 (1) in MeCN at a Pt electrode. The crystals harvested from the cathode were found to be the unprecedented mixed-valence 1-D chain compound [RhI,II(MeCN)4(BF4)1.5] x (5), which result from a radical polymerization of the unstable Rh2 I,II dinuclear cation. In an effort to access the final member of this series, namely, the homoleptic RhI species, the dicarbonyl compound [RhI(CO)2(MeCN)2][BF4] (6) was prepared, but all thermal and photochemical attempts to remove the CO ligands led to the conclusion that only one CO is labile. The mixed-ligand, square planar cation [RhI(CO)2(MeCN)2]+ was found to form a 1-D stack in the solid state, unlike previously reported salts with bulky counterions. For all of the compounds under investigation, infrared spectroscopy and X-ray studies were performed. The mixed-valence product was also characterized by EPR spectroscopy and SQUID magnetometry.

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Section: Resultsmentioning

confidence: 99%

A Remarkable Family of Rhodium Acetonitrile Compounds Spanning Three Oxidation States and with Nuclearities Ranging from Mononuclear and Dinuclear to One-Dimensional Chains

et al. 1999

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“…The less stable adducts in the isolated band are most likely ax-DNA species, which are expected to exhibit enhanced exchange rates with heating as compared to eq-DNA adducts. 55 The reversal of additional dsDNA-dirhodium adducts in the isolated band by further heating in 40 mM thiourea indicates the presence of another subset of products that are stable to more harsh conditions (most likely eq-DNA adducts). The lability of the dirhodium leaving groups corresponds to the extent of interstrand cross-link formation on a 123 bp DNA fragment, as indicated by denaturing polyacrylamide gel electrophoresis (dPAGE) studies, and is in the order Rh + , which may be due to its ability to intercalate DNA bases.…”

Section: And H-h Cis-[rhmentioning

confidence: 99%

“…These findings refute earlier claims that no reaction between dirhodium compounds and dsDNA occurs. , The reversal behavior of the dsDNA interstrand cross-links in 5 M urea at 95 °C implies the presence of a mixture of monofunctional or bifunctional adducts possibly bound at ax − ax , ax − eq , or eq − eq sites of the dirhodium core. The less stable adducts in the isolated band are most likely ax -DNA species, which are expected to exhibit enhanced exchange rates with heating as compared to eq -DNA adducts . The reversal of additional dsDNA−dirhodium adducts in the isolated band by further heating in 40 mM thiourea indicates the presence of another subset of products that are stable to more harsh conditions (most likely eq -DNA adducts).…”

Section: Interactions With Nucleobases and Nucleos(t)idesmentioning

confidence: 99%

Interactions of Metal−Metal-Bonded Antitumor Active Complexes with DNA Fragments and DNA

2005

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This Account summarizes the DNA binding properties of anticancer active dinuclear Rh, Re, and Ru compounds. The combined results of NMR spectroscopy, X-ray crystallography, and various biochemical tools provide incontrovertible evidence that dinuclear complexes are favorably poised to bind to purine nucleobases, DNA fragments, and double-stranded DNA. Moreover, direct DNA photocleavage in vitro is effected by dirhodium compounds in the presence of electron acceptors in solution or directly attached to the dirhodium core. This research has provided valuable insight in the interactions of dinuclear compounds with DNA, knowledge that is an excellent backdrop for rational design of promising dinuclear drugs.

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“…are most likely ax DNA adducts which are expected to exhibit enhanced exchange rates upon heating as compared to eq DNA adducts(65). This argument is supported by the fact that, for [Rh 2 (eq-H 2 O) 8 (ax-H 2 O) 2 ] 4+ , the rate of exchange of the ax H 2 O molecules is 3 orders of magnitude higher than those in eq positions(65). Moreover, the Rh-N distances to an eq and ax CH 3 CN molecule in cis-[Rh 2 (O 2 -CCH 3 ) 2 (NCCH 3 ) 6 ](BF 4 ) 2 of 1.985(4) and 2.232(4) Å, respectively…”

mentioning

confidence: 99%

Covalent Binding and Interstrand Cross-Linking of Duplex DNA by Dirhodium(II,II) Carboxylate Compounds

et al. 2004

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The study of the interactions of double-stranded (ds) DNA with the dirhodium carboxylate compounds Rh(2)(O(2)CCH(3))(4)(H(2)O)(2) (Rh1), [Rh(2)(O(2)CCH(3))(2)(CH(3)CN)(6)](BF(4))(2) (Rh2), and Rh(2)(O(2)CCF(3))(4) (Rh3) supports the presence of covalently linked DNA adducts, including stable DNA interstrand cross-links. The present biochemical study refutes earlier claims that no reaction between dirhodium compounds and dsDNA occurs. The reversal behavior of these interstrand cross-links in 5 M urea at 95 degrees C (for different heating times) implies the presence of various coordination modes involving ax/ax, ax/eq, and eq/eq DNA interactions with the dirhodium core. The reaction rates of the dirhodium compounds with dsDNA were determined spectroscopically and are in the order Rh1 << Rh2 < Rh3. This difference in behavior of the three dirhodium compounds correlates with the lability of the leaving groups and corresponds to the extent of interstrand cross-link formation by these compounds on a 123 bp DNA fragment, as observed by denaturing polyacrylamide gel electrophoresis (dPAGE). Since all three dirhodium compounds form covalent Rh-DNA adducts, including interstrand cross-links, it is important that DNA be considered a potential target for biological activity of these dirhodium carboxylate compounds.

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High-pressure proton NMR study of acetonitrile exchange kinetics on [Rh2(CH3CN)10]4+ and 17O NMR investigation of aqueous solutions of [Rh2(H2O)10]4 +

Cited by 20 publications

References 30 publications

A Remarkable Family of Rhodium Acetonitrile Compounds Spanning Three Oxidation States and with Nuclearities Ranging from Mononuclear and Dinuclear to One-Dimensional Chains

A Remarkable Family of Rhodium Acetonitrile Compounds Spanning Three Oxidation States and with Nuclearities Ranging from Mononuclear and Dinuclear to One-Dimensional Chains

Interactions of Metal−Metal-Bonded Antitumor Active Complexes with DNA Fragments and DNA

Covalent Binding and Interstrand Cross-Linking of Duplex DNA by Dirhodium(II,II) Carboxylate Compounds

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