Rudi Van Eldik - Academia.edu (original) (raw)
Papers by Rudi Van Eldik
Frontiers in Chemistry
Recently, we investigated the substitution behavior of a series of ruthenium(II) complexes of the... more Recently, we investigated the substitution behavior of a series of ruthenium(II) complexes of the general formula [RuII(terpy)(N∧N)Cl]Cl, where terpy = 2,2′:6′,2″-terpyridine, N∧N = bidentate ligand, in aqueous solutions. We have shown that the most and least reactive complexes of the series are [RuII(terpy)(en)Cl]Cl (en = ethylenediamine) and [RuII(terpy)(phen)Cl]Cl (phen = 1, 10-phenantroline), respectively, as a result of different electronic effects provided by the bidentate spectator chelates. Polypyridyl amine Ru(II) complex, viz. [Ru(terpy)(en)Cl]Cl and [Ru(terpy)(ampy)Cl]Cl (where ampy = 2-(aminomethyl)pyridine), in which the terpy chelate labilizes the metal center, are able to catalyze the conversion of NAD+ to 1,4-NADH using sodium formate as a source of hydride. We showed that this complex can control the [NAD+]/[NADH] ratio and potentially induce reductive stress in living cells, which is accepted as an effective method to kill cancer cells. Polypyridyl Ru(II) complexes...
Chemie in unserer Zeit, 2000
Ist der Reaktionsmechanismus bekannt, kann eine chemische Reaktion gezielter gelenkt werden. Viel... more Ist der Reaktionsmechanismus bekannt, kann eine chemische Reaktion gezielter gelenkt werden. Viele anorganische Reaktionen konnten lange Zeit mit konventionellen kinetischen Untersuchungsmethoden nicht eindeutig mechanistisch zugeordnet werden; erst unter hohem Druck gelang es, ihre Mechanismen aufzuklaren.
Atmospheric Environment, 1999
Conductometry was used to study the kinetics of the oxidation of hydrogen sulfite, HSO−3, by hydr... more Conductometry was used to study the kinetics of the oxidation of hydrogen sulfite, HSO−3, by hydrogen peroxide in aqueous non-buffered solution at the low concentration level of 10−5–10−6M, typically found in cloud water. The kinetic data confirm that the rate law reported for the pH range 3–6 at higher concentration levels, rate=kH·[H+]·[HSO−3]·[H2O2], is valid at the low concentration level and at low ionic strength Ic. At 298K and Ic=1.5×10−4M, third-order rate constant kH was found to be kH=(9.1±0.5)×107M−2s−1. The temperature dependence of kH led to an activation energy of Ea=29.7±0.9kJmol−1. The effect of the ionic strength (adjusted with NaCl) on rate constant kH was studied in the range Ic=2×10−4–5.0M at pH=4.5–5.2 by conductometry and stopped-flow spectrophotometry. The dependence of kH on Ic can be described with a semi-empirical relationship, which is useful for the purpose of comparison and extrapolation. The kinetic data obtained are critically compared with those reported earlier.
Journal of Electroanalytical Chemistry, 2011
Electrochemical properties of a 1-hydroxy-anthraquinone derivative (1-hydroxyAQ) self-assembled m... more Electrochemical properties of a 1-hydroxy-anthraquinone derivative (1-hydroxyAQ) self-assembled monolayer (SAM) were studied using reflectance infrared, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results of the electrochemical investigation into the proton-coupled electron transfer (PCET) reaction at various pHs and temperatures demonstrate a strong pH-charge transfer rate dependence. The charge transfer rates are faster in both acidic and basic solutions than near physiological pH. Interestingly, the activation enthalpy for the charge transfer reactions at physiological pH is low at 23 kJ mol À1 compared to 67 kJ mol À1 at pH 1.5. Variable temperature studies showed the entropic cost associated with the charge transfer reaction at pH 7.5 causes the slow charge transfer rate and suggests that pre-organizing proton donor solvents could lead to very fast charge transfer reactions at the hydrophobic|hydrophilic interface.
Journal of the Chemical Society, Faraday Transactions, 1995
The kinetics of thermal self-exchange and cross reactions between cyanometallate ions have been s... more The kinetics of thermal self-exchange and cross reactions between cyanometallate ions have been studied by various techniques.'-8 The rate constants were observed to depend strongly on the nature and concentrations of cations present in solution. This catalytic activity of ...
Chemie in unserer Zeit, 2000
![Research paper thumbnail of Hydrogen Cyanide Exchange on [Al(HCN) 6 ] 3+ - A DFT Study](https://attachments.academia-assets.com/99483709/thumbnails/1.jpg)
](Zeitschrift für anorganische und allgemeine Chemie, 2009
The hydrogen cyanide exchange mechanism of [Al(HCN) 6 ] 3ϩ has been investigated by DFT calculati... more The hydrogen cyanide exchange mechanism of [Al(HCN) 6 ] 3ϩ has been investigated by DFT calculations (B3LYP/ 6-311ϩG**). The calculations provide theoretical evidence that the hydrogen cyanide exchange proceeds via a limiting dissociative (D) mechanism involving a stable five-coordinate intermediate [Al(HCN) 5 • (HCN) 2 ] 3ϩ. The activation energy for the D-mechanism is 23.4 kcal • mol Ϫ1 , which is 2.8 kcal • mol Ϫ1 lower than for the
Transition Metal Chemistry, 1987
The solvent, pressure, and temperature-dependence of the lowest energy metal-to-ligand charge-tra... more The solvent, pressure, and temperature-dependence of the lowest energy metal-to-ligand charge-transfer absorption bands are reported for a series of [Mo(CO)4(LL)], compounds where LL is a bidentate diimine ligand containing the chelating fragment-N=CRCR=N-, and one terdentate ligand analogue [Mo(CO)3(LLL)]. The effects of ligand nature on these dependences are discussed, as are their interrelations and their connection with solvent properties such as polarity.
![Research paper thumbnail of Multistep Oxidation Kinetics of [FeII(cdta)] [cdta = N,N,N,N-(1,2-Cyclohexanediamine)tetraacetate] with Molecular Oxygen](https://attachments.academia-assets.com/99483707/thumbnails/1.jpg)
](European Journal of Inorganic Chemistry, 1999
The complicated oxidation kinetics of the reaction of reacts with O 2 by a substitution process t... more The complicated oxidation kinetics of the reaction of reacts with O 2 by a substitution process to form [Fe II (cdta)O 2 ] 2-; (2) electron-transfer to form an Fe III-[Fe II (cdta)] [cdta = 1,2-(N,NЈ-cyclohexanediamine)tetraacetate] with molecular oxygen was investigated as a superoxo species; (3) subsequent bridge formation followed by electron-transfer to give [(cdta)Fe III-O 2 2-Fe III (cdta)] 4-; function of [Fe II ], [O 2 ], pH, temperature and pressure. In the presence of an excess of [Fe II (cdta)] three steps could be and (4) a fast decomposition of the peroxide intermediate yielding the monomeric [Fe III (cdta)] and H 2 O 2. Rate and observed, for which the following rate constants were found at 25°C; k 1 = 1080 ± 16 M-1 s-1 , k 2 = 103 ± 4 M-1 s-1 and k 3 = activation parameters for these steps are reported and discussed in terms of the postulated mechanism and in 59 ± 5 M-1 s-1. These reaction steps can be accounted for in terms of the following mechanism: (1) [Fe II (cdta)H 2 O] 2reference to available literature data. The present work describes how the selected chelate can Kinetic Measurements [a] Institute for Inorganic Chemistry, University of Erlangen-Kinetic traces measured in the presence of an excess of Nürnberg, [Fe II (cdta)] showed a complicated multistep process. In con-Egerlandstraße 1, 91058 Erlangen, Germany trast to the [Fe II (edta)] system, we could now fit the kinetic
JBIC Journal of Biological Inorganic Chemistry, 1997
The kinetics of Fe(III) complexation by lipophilic 3-hydroxy-2-methyl-l(γ-stearoamidopropyl)-4-py... more The kinetics of Fe(III) complexation by lipophilic 3-hydroxy-2-methyl-l(γ-stearoamidopropyl)-4-pyridinone (HMSP) were studied when [Fe(III)] > [HMSP] in MeOH/H2O mixed solvent and [Fe(III)] < [HMSP] in MeOH, respectively. When Fe(III) was in excess, the observed rate constants depend on [Fe(III)]2 tot and on the reciprocal of [H+] and decrease with increasing pressure. ΔV ‡ values are around +8.0 cm3 mol–1. A mechanism consisting
Chemistry - A European Journal, 1999
Skip to Main Content. ...
Inorganic Chemistry, 1994
Journal of the Chemical Society Dalton Transactions
Inorganic Chemistry, 1992
The equilibrium constants for the stepwise substitution of biquinolyl (biq) by 2,9-dimethylphenan... more The equilibrium constants for the stepwise substitution of biquinolyl (biq) by 2,9-dimethylphenanthroline (dmp) in C~(b i q)~+ were determined in acetone and methanol solutions by UV-visible spectroscopy. The kinetics of the mixed-ligand complex formation in these two solvents were studied by means of the stopped-flow method. The formation of Cu(biq)(dmp)+ follows two parallel pathways: a direct reaction via an outer-sphere encounter complex and a solvent-assisted path via an intermediate in which one biq ligand is fully dissociated. Unexpectedly, the rate behavior is quite different in these two solvents. In acetone the overall rate constant for the direct reaction, kI2 = K,kI, is 1.8 X lo3 M-' s-I with k, = 2.9 X 102 s-l. The solvent-assisted pathway is of minor importance. In methanol k12 is 7 M-' s-' and kI = 1.1 s-l. The rates for the direct pathway and the solvent pathway are similar. The ligand dependence (dmp, phen) of kI in acetone shows that an associative activation mode is preferred. Preliminary experiments showed that substitution reactions at various Cu(1) complexes in acetonitrile are too fast to be studied with the stopped-flow method. Surprisingly, however, in acetone (7) See, for example: (a) Copper in Coordination Chemistry: Biochemical and Inorganic Perspectives;
Inorganic Chemistry, 1986
... Partial molar volumes were determined from density measurements at 298.000 f 0.002 K using an... more ... Partial molar volumes were determined from density measurements at 298.000 f 0.002 K using an Anton Paar DMA 02/C digital precision densimeter. ... Chem. SOC. 1985, 107, 4799. (36) Fialkow, JJ; Zytomirski, A. N.; Tarasenko, JA Chemiafizyczna roztworow niewodnych; PAN ...
and 1,1-cyclobutanedicarboxylate have been studied. The stoichiometry and stability constants of ... more and 1,1-cyclobutanedicarboxylate have been studied. The stoichiometry and stability constants of the formed complexes are reported, and the concentration distribution of the various complex species has been evaluated as a function of pH. The kinetics and mechanism of the complexformation reactions were studied as a function of nucleophile concentration, temperature and pressure. Two consecutive reaction steps, which both depend on the nucleophile concentration, were observed under all conditions. The negative entropies and volumes of activation support the operation of an associative complex-formation mechanism. The results are compared and discussed in reference to data reported for closely related systems in the literature.
High Pressure Food Science, Bioscience and Chemistry, 1998
![Research paper thumbnail of Equilibrium, kinetic and solvent effect studies on the reactions of [RuIII(Hedta)(H2O)] with thiols](https://attachments.academia-assets.com/73475859/thumbnails/1.jpg)
](Dalton Transactions, 2005
Frontiers in Chemistry
Recently, we investigated the substitution behavior of a series of ruthenium(II) complexes of the... more Recently, we investigated the substitution behavior of a series of ruthenium(II) complexes of the general formula [RuII(terpy)(N∧N)Cl]Cl, where terpy = 2,2′:6′,2″-terpyridine, N∧N = bidentate ligand, in aqueous solutions. We have shown that the most and least reactive complexes of the series are [RuII(terpy)(en)Cl]Cl (en = ethylenediamine) and [RuII(terpy)(phen)Cl]Cl (phen = 1, 10-phenantroline), respectively, as a result of different electronic effects provided by the bidentate spectator chelates. Polypyridyl amine Ru(II) complex, viz. [Ru(terpy)(en)Cl]Cl and [Ru(terpy)(ampy)Cl]Cl (where ampy = 2-(aminomethyl)pyridine), in which the terpy chelate labilizes the metal center, are able to catalyze the conversion of NAD+ to 1,4-NADH using sodium formate as a source of hydride. We showed that this complex can control the [NAD+]/[NADH] ratio and potentially induce reductive stress in living cells, which is accepted as an effective method to kill cancer cells. Polypyridyl Ru(II) complexes...
Chemie in unserer Zeit, 2000
Ist der Reaktionsmechanismus bekannt, kann eine chemische Reaktion gezielter gelenkt werden. Viel... more Ist der Reaktionsmechanismus bekannt, kann eine chemische Reaktion gezielter gelenkt werden. Viele anorganische Reaktionen konnten lange Zeit mit konventionellen kinetischen Untersuchungsmethoden nicht eindeutig mechanistisch zugeordnet werden; erst unter hohem Druck gelang es, ihre Mechanismen aufzuklaren.
Atmospheric Environment, 1999
Conductometry was used to study the kinetics of the oxidation of hydrogen sulfite, HSO−3, by hydr... more Conductometry was used to study the kinetics of the oxidation of hydrogen sulfite, HSO−3, by hydrogen peroxide in aqueous non-buffered solution at the low concentration level of 10−5–10−6M, typically found in cloud water. The kinetic data confirm that the rate law reported for the pH range 3–6 at higher concentration levels, rate=kH·[H+]·[HSO−3]·[H2O2], is valid at the low concentration level and at low ionic strength Ic. At 298K and Ic=1.5×10−4M, third-order rate constant kH was found to be kH=(9.1±0.5)×107M−2s−1. The temperature dependence of kH led to an activation energy of Ea=29.7±0.9kJmol−1. The effect of the ionic strength (adjusted with NaCl) on rate constant kH was studied in the range Ic=2×10−4–5.0M at pH=4.5–5.2 by conductometry and stopped-flow spectrophotometry. The dependence of kH on Ic can be described with a semi-empirical relationship, which is useful for the purpose of comparison and extrapolation. The kinetic data obtained are critically compared with those reported earlier.
Journal of Electroanalytical Chemistry, 2011
Electrochemical properties of a 1-hydroxy-anthraquinone derivative (1-hydroxyAQ) self-assembled m... more Electrochemical properties of a 1-hydroxy-anthraquinone derivative (1-hydroxyAQ) self-assembled monolayer (SAM) were studied using reflectance infrared, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results of the electrochemical investigation into the proton-coupled electron transfer (PCET) reaction at various pHs and temperatures demonstrate a strong pH-charge transfer rate dependence. The charge transfer rates are faster in both acidic and basic solutions than near physiological pH. Interestingly, the activation enthalpy for the charge transfer reactions at physiological pH is low at 23 kJ mol À1 compared to 67 kJ mol À1 at pH 1.5. Variable temperature studies showed the entropic cost associated with the charge transfer reaction at pH 7.5 causes the slow charge transfer rate and suggests that pre-organizing proton donor solvents could lead to very fast charge transfer reactions at the hydrophobic|hydrophilic interface.
Journal of the Chemical Society, Faraday Transactions, 1995
The kinetics of thermal self-exchange and cross reactions between cyanometallate ions have been s... more The kinetics of thermal self-exchange and cross reactions between cyanometallate ions have been studied by various techniques.'-8 The rate constants were observed to depend strongly on the nature and concentrations of cations present in solution. This catalytic activity of ...
Chemie in unserer Zeit, 2000
Zeitschrift für anorganische und allgemeine Chemie, 2009
The hydrogen cyanide exchange mechanism of [Al(HCN) 6 ] 3ϩ has been investigated by DFT calculati... more The hydrogen cyanide exchange mechanism of [Al(HCN) 6 ] 3ϩ has been investigated by DFT calculations (B3LYP/ 6-311ϩG**). The calculations provide theoretical evidence that the hydrogen cyanide exchange proceeds via a limiting dissociative (D) mechanism involving a stable five-coordinate intermediate [Al(HCN) 5 • (HCN) 2 ] 3ϩ. The activation energy for the D-mechanism is 23.4 kcal • mol Ϫ1 , which is 2.8 kcal • mol Ϫ1 lower than for the
Transition Metal Chemistry, 1987
The solvent, pressure, and temperature-dependence of the lowest energy metal-to-ligand charge-tra... more The solvent, pressure, and temperature-dependence of the lowest energy metal-to-ligand charge-transfer absorption bands are reported for a series of [Mo(CO)4(LL)], compounds where LL is a bidentate diimine ligand containing the chelating fragment-N=CRCR=N-, and one terdentate ligand analogue [Mo(CO)3(LLL)]. The effects of ligand nature on these dependences are discussed, as are their interrelations and their connection with solvent properties such as polarity.
European Journal of Inorganic Chemistry, 1999
The complicated oxidation kinetics of the reaction of reacts with O 2 by a substitution process t... more The complicated oxidation kinetics of the reaction of reacts with O 2 by a substitution process to form [Fe II (cdta)O 2 ] 2-; (2) electron-transfer to form an Fe III-[Fe II (cdta)] [cdta = 1,2-(N,NЈ-cyclohexanediamine)tetraacetate] with molecular oxygen was investigated as a superoxo species; (3) subsequent bridge formation followed by electron-transfer to give [(cdta)Fe III-O 2 2-Fe III (cdta)] 4-; function of [Fe II ], [O 2 ], pH, temperature and pressure. In the presence of an excess of [Fe II (cdta)] three steps could be and (4) a fast decomposition of the peroxide intermediate yielding the monomeric [Fe III (cdta)] and H 2 O 2. Rate and observed, for which the following rate constants were found at 25°C; k 1 = 1080 ± 16 M-1 s-1 , k 2 = 103 ± 4 M-1 s-1 and k 3 = activation parameters for these steps are reported and discussed in terms of the postulated mechanism and in 59 ± 5 M-1 s-1. These reaction steps can be accounted for in terms of the following mechanism: (1) [Fe II (cdta)H 2 O] 2reference to available literature data. The present work describes how the selected chelate can Kinetic Measurements [a] Institute for Inorganic Chemistry, University of Erlangen-Kinetic traces measured in the presence of an excess of Nürnberg, [Fe II (cdta)] showed a complicated multistep process. In con-Egerlandstraße 1, 91058 Erlangen, Germany trast to the [Fe II (edta)] system, we could now fit the kinetic
JBIC Journal of Biological Inorganic Chemistry, 1997
The kinetics of Fe(III) complexation by lipophilic 3-hydroxy-2-methyl-l(γ-stearoamidopropyl)-4-py... more The kinetics of Fe(III) complexation by lipophilic 3-hydroxy-2-methyl-l(γ-stearoamidopropyl)-4-pyridinone (HMSP) were studied when [Fe(III)] > [HMSP] in MeOH/H2O mixed solvent and [Fe(III)] < [HMSP] in MeOH, respectively. When Fe(III) was in excess, the observed rate constants depend on [Fe(III)]2 tot and on the reciprocal of [H+] and decrease with increasing pressure. ΔV ‡ values are around +8.0 cm3 mol–1. A mechanism consisting
Chemistry - A European Journal, 1999
Skip to Main Content. ...
Inorganic Chemistry, 1994
Journal of the Chemical Society Dalton Transactions
Inorganic Chemistry, 1992
The equilibrium constants for the stepwise substitution of biquinolyl (biq) by 2,9-dimethylphenan... more The equilibrium constants for the stepwise substitution of biquinolyl (biq) by 2,9-dimethylphenanthroline (dmp) in C~(b i q)~+ were determined in acetone and methanol solutions by UV-visible spectroscopy. The kinetics of the mixed-ligand complex formation in these two solvents were studied by means of the stopped-flow method. The formation of Cu(biq)(dmp)+ follows two parallel pathways: a direct reaction via an outer-sphere encounter complex and a solvent-assisted path via an intermediate in which one biq ligand is fully dissociated. Unexpectedly, the rate behavior is quite different in these two solvents. In acetone the overall rate constant for the direct reaction, kI2 = K,kI, is 1.8 X lo3 M-' s-I with k, = 2.9 X 102 s-l. The solvent-assisted pathway is of minor importance. In methanol k12 is 7 M-' s-' and kI = 1.1 s-l. The rates for the direct pathway and the solvent pathway are similar. The ligand dependence (dmp, phen) of kI in acetone shows that an associative activation mode is preferred. Preliminary experiments showed that substitution reactions at various Cu(1) complexes in acetonitrile are too fast to be studied with the stopped-flow method. Surprisingly, however, in acetone (7) See, for example: (a) Copper in Coordination Chemistry: Biochemical and Inorganic Perspectives;
Inorganic Chemistry, 1986
... Partial molar volumes were determined from density measurements at 298.000 f 0.002 K using an... more ... Partial molar volumes were determined from density measurements at 298.000 f 0.002 K using an Anton Paar DMA 02/C digital precision densimeter. ... Chem. SOC. 1985, 107, 4799. (36) Fialkow, JJ; Zytomirski, A. N.; Tarasenko, JA Chemiafizyczna roztworow niewodnych; PAN ...
and 1,1-cyclobutanedicarboxylate have been studied. The stoichiometry and stability constants of ... more and 1,1-cyclobutanedicarboxylate have been studied. The stoichiometry and stability constants of the formed complexes are reported, and the concentration distribution of the various complex species has been evaluated as a function of pH. The kinetics and mechanism of the complexformation reactions were studied as a function of nucleophile concentration, temperature and pressure. Two consecutive reaction steps, which both depend on the nucleophile concentration, were observed under all conditions. The negative entropies and volumes of activation support the operation of an associative complex-formation mechanism. The results are compared and discussed in reference to data reported for closely related systems in the literature.
High Pressure Food Science, Bioscience and Chemistry, 1998
Dalton Transactions, 2005