Israel Zilberman - Academia.edu (original) (raw)
Papers by Israel Zilberman
Characterization of the thin films consisting of an amphiphilic fulleropyrrolidine and a novel wa... more Characterization of the thin films consisting of an amphiphilic fulleropyrrolidine and a novel water soluble porphyrin using Langmuir-ShA¤fer (LS) was investigated. The characterization of the LS films by UV-Vis spectroscopy revealed that the UV region was dominated by optical absorptions of the C60 subunits, while the porphyrin absorptions were very weak in this region. The use of polarized light suggested the existence of a preferential direction of macrocycle rings with an edge-on arrangement with respect to the substrate surface. The films deposited onto ITO substrates in which the floating films were transferred onto the ITO electrodes by the LS method at several surface pressures were also investigated.
Chemcatchem, Aug 10, 2016
Methyl radicals react with platinum nanoparticles (NPs) suspended in aqueous solutions to form (P... more Methyl radicals react with platinum nanoparticles (NPs) suspended in aqueous solutions to form (Pt 0-NPs)-(CH 3) n as a stable major product. Hydrogen gas treatment of the Pt 0-NPs affects the composition of the products and the surface reactions. The results clearly point out that pretreatment of Pt 0-NPs and (Pt 0-NPs)-(CH 3) n with H 2 considerably affects their reactions with methyl radicals. The implications of the results on catalytic processes are discussed.
Inorganic Chemistry
Conjugated arrays composed of corrole macrocycles are increasingly more common, but their chemist... more Conjugated arrays composed of corrole macrocycles are increasingly more common, but their chemistry still lags behind that of their porphyrin counterparts. Here, we report on the insertion of iron(III) into a β,β-fused corrole dimer and on the electronic effects that this redox active metal center has on the already rich coordination chemistry of [H 3 tpfc] COT, where COT = cyclo-octatetraene and tpfc = tris(pentafluorophenyl)corrole. Synthetic manipulations were performed for the isolation and full characterization of both the 5-coordinate [Fe III tpfc(py)] 2 COT and 6-coordinate [Fe III tpfc(py) 2 ] 2 COT, with one and two axial pyridine ligands per metal, respectively. X-Ray crystallography reveals a dome-shaped structure for [Fe III tpfc(py)] 2 COT and a perfectly planar geometry which (surprisingly at first) is also characterized by shorter Fe−N (corrole) and Fe−N (pyridine) distances. Computational investigations clarify that the structural phenomena are due to a change in the iron(III) spin state from intermediate (S = 3/2) to low (S = 1/2), and that both the 5-and 6-coordinated complexes are enthalpically favored. Yet, in contrast to iron(III) porphyrins, the formation enthalpy for the coordination of the first pyridine to Fe(III) corrole is more negative than that of the second pyridine coordination. Possible interactions between the two corrole subunits and the chelated iron ions were examined by UV−Vis spectroscopy, electrochemical techniques, and density functional theory (DFT). The large differences in the electronic spectra of the dimer relative to the monomer are concluded to be due to a reduced electronic gap, owing to the extensive electron delocalization through the fusing bridge. A cathodic sweep for the dimer discloses two redox processes, separated by 230 mV. The DFT self-consistent charge density for the neutral and cationic states (1-and 2-electron oxidized) reveals that the holes are localized on the macrocycle. A different picture emerges from the reduction process, where both the electrochemistry and the calculated charge density point toward two consecutive electron transfers with similar energetics, indicative of very weak electron communication between the two redox active iron(III) sites. The binuclear complex was determined to be a much better catalyst for the electrochemical hydrogen evolution reaction (HER) than the analogous mononuclear corrole.
Chemistry – A European Journal
Journal of Inorganic Biochemistry
Free Radical Biology and Medicine, 2021
The mechanism of reaction of DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) with... more The mechanism of reaction of DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) with ·CH3, CH3O2· and ·OH radicals were studied. The radicals were formed in situ radiolytically. The methyl radicals react orders of magnitude slower with DOTA and with MIII(DOTA)- than the hydroxyl radicals. The various final products were identified and mechanisms for their formation are proposed. CH3O2· radicals do not react, or react too slowly to be observed, with DOTA and with MIII(DOTA)- as long as the central cation is not oxidized by the peroxyl radical. The results imply that synthesis of the MIII(DOTA)-(MIII = radioisotope) complexes in a water-organic solvent (ethanol or 2-propanol or acetonitrile) mixture is not only kinetically desired but the so formed complex also decreases the radiolytic decomposition of DOTA.
Inorganica Chimica Acta, 2020
Abstract The reactions of the radicals R, R = CH3 or CH2OH, with the complex CuII(ntp)(H2O) were ... more Abstract The reactions of the radicals R, R = CH3 or CH2OH, with the complex CuII(ntp)(H2O) were studied. The kinetics of formation of the transient complexes (ntp)CuIII-R fit pseudo first order rate laws. The mechanism of decomposition of the transient complex (ntp)CuIII-CH3 at pH ≥ 7 involves homolysis of the CuIII-C bond. However, at pH
European Journal of Inorganic Chemistry, 2021
Advanced oxidation technologies often use peroxymonosulfate in the presence of CoIIaq. It is comm... more Advanced oxidation technologies often use peroxymonosulfate in the presence of CoIIaq. It is commonly assumed that the reaction of Co(H2O)62+ with HSO5− yields CoIIIaq and SO4.−. DFT results point out that first CoII(SO5)(H2O)2 is formed. The homolysis of CoII(SO5)(H2O)2 to yield (H2O)CoII(SO5)OH.+SO4.−, is exothermic but has a large activation energy. However the cobalt is not oxidized in this reaction. CoII(SO5)(H2O)2 reacts with a second HSO5− to form CoII(SO5)2(H2O)2− that decomposes via disproportionation of the monoperoxysulfate ions without oxidation of the central cobalt ion. Surprisingly even in the presence of ligands, L, that stabilize CoIII, i. e., pyrophosphate; tri‐polyphosphate and ATP, the experimentally observed reaction mechanism involves the formation of LCoII‐OOSO3aq which then reacts with another HSO5− to form LCoII‐(OOSO32−)2. The latter complex decomposes via disproportionation of the monoperoxysulfate ligands followed by oxidation of the central cobalt cation...
Chemistry – A European Journal, 2021
Two new aqueous UIV complexes were synthesized by the interaction between the tetravalent uranium... more Two new aqueous UIV complexes were synthesized by the interaction between the tetravalent uranium cation and the (1,4,7,10‐Tetraazacyclododecane‐1,4,7,10‐tetra(methylene phosphonic acid) (DOTP) macrocyclic ligand. Two distinct homonuclear complexes were identified; the first was characterized by X‐ray crystallography as a unique “out‐of‐cage”, [U(DOTPH6)2] complex, in which the UIV cation is octa‐coordinated to 4 phosphonic arms from each ligand in a square anti‐prism geometry, with a C4 symmetry. The second is the “in‐cage” [U(DOTPH4)] complex, in which the tetravalent cation is located between the macrocycle O4 and N4 planes. With the help of UV‐Vis absorption, 1H/31P NMR, ATR‐IR, and MALDI‐TOFMS analytical techniques, the chemical interchange between both species is presented. It is shown that the one‐way transition is governed by the formation of a multiple number of soluble oligomeric species consisting of varied stoichiometric ratios of both characterized homonuclear complexes.
ChemPhysChem, 2020
Supporting information for this article is given via a link at the end of the document.
Free Radical Biology and Medicine, 2021
Methyl radicals play key roles in various chemical and biological processes. Mechanistic studies ... more Methyl radicals play key roles in various chemical and biological processes. Mechanistic studies of methyl radicals with their precursor, Dimethyl Sulfoxide (DMSO), were extensively studied. Though the involved mechanisms seemed to be clarified, essentially none of the studies have been performed at conditions relevant to both biological and catalytic systems, i.e. low steady state radical concentrations. A chain-like reaction, as an inverse function of the radicals concentrations ([•CH3]ss), increases the methyl radical yields. The nature of the additional products obtained differs from those commonly observed. Furthermore it is shown that methyl radicals abstract a methyl group from DMSO to yield ethane. Herein we report a novel mechanism relevant mainly at low steady state radical concentrations, which may change the understanding of certain reaction routes present in both biological systems and catalytic chemical systems. Thus the results point out that mechanistic studies have to be carried out at dose rates forming radicals at analogous concentrations to those present in the process of interest.
Chemistry – A European Journal, 2020
The 1,4,7,10‐tetrazacyclodecane‐1,4,7,10‐tetraacetic acid (DOTA) aqueous complex of UIV with H2O,... more The 1,4,7,10‐tetrazacyclodecane‐1,4,7,10‐tetraacetic acid (DOTA) aqueous complex of UIV with H2O, OH−, and F− as axial ligands was studied by using UV/Vis spectrophotometry, ESI‐MS, NMR spectroscopy, X‐ray crystallography, and electrochemistry. The UIV–DOTA complex with either water or fluoride as axial ligands was found to be inert to oxidation by molecular oxygen, whereas the complex with hydroxide as an axial ligand slowly hydrolyzed and was oxidized by dioxygen to a diuranate precipitate. The combined data set acquired shows that, although axial substitution of fluoride and hydroxide ligands instead of water does not seem to significantly change the aqueous DOTA complex structure, it has an important effect on the electronic configuration of the complex. The UIV/UIII redox couple was found to be quasi‐reversible for the complex with both axially bonded H2O and hydroxide, but irreversible for the complex with axially bonded fluoride. Intriguingly, binding of the axial fluoride re...
Journal of Coordination Chemistry, 2019
Abstract The reactions of methyl radicals with MII-(ntp)(H2O)2 complexes were studied. The format... more Abstract The reactions of methyl radicals with MII-(ntp)(H2O)2 complexes were studied. The formation of an unstable intermediate (ntp)(H2O)MIII-CH3 is observed. This reaction is an equilibrium process, i.e. the MIII-C bond decomposes via homolysis. The (ntp)(H2O)MIII-CH3 complexes isomerize to a more stable form. The results compared to those obtained in analogous reactions of the MII-(nta)(H2O)2 complexes were shown to be similar with one exception – for the nta complexes no isomerization process is observed. Graphical Abstract
Journal of Coordination Chemistry, 2018
The reaction kinetics of eight amino-carboxylate complexes of Fe(III) and Mn(II) with carbonate r... more The reaction kinetics of eight amino-carboxylate complexes of Fe(III) and Mn(II) with carbonate radical anion were studied using the pulse radiolysis method and UV-vis spectroscopy. Difference spectra revealed the formation of Fe(IV) and Mn(III) after reaction with CO 3 •-. Spectral measurements revealed the first step to be the coordination of carbonate to the metal center. All of these led to the conclusion that the role of coordinated carbonate is essential to the electron transfer process by carbonate radical anion.
Journal of Coordination Chemistry, 2018
During an effort to synthesize the trans-III-copper(II) complex with 1,4,8,11-tetramethyl-pyropho... more During an effort to synthesize the trans-III-copper(II) complex with 1,4,8,11-tetramethyl-pyrophosphonate-1,4,8,11-tetra-aza-cyclo-tetradecane, using only perchlorate salts, it was noted that the perchlorate is reduced to chloride. Analysis of the reactions leading to this surprising result points out that Cu(H 2 O) 4 2+ catalyzes the reduction of perchlorate by H 2 and by CH 2 O. These reactions are slow at room temperature and ambient pressures. A plausible mechanism, supported by DFT calculations, is proposed pointing out that the role of CuH + under mild conditions cannot be ignored.
![Research paper thumbnail of Mechanistic Studies on the Role of [CuII(CO3)n]2−2n as a Water Oxidation Catalyst: Carbonate as a Non‐Innocent Ligand](https://attachments.academia-assets.com/116764729/thumbnails/1.jpg)
](Chemistry – A European Journal, 2017
Recently it was reported that copper bicarbonate/carbonate complexes are good electro‐catalysts f... more Recently it was reported that copper bicarbonate/carbonate complexes are good electro‐catalysts for water oxidation. However, the results did not enable a decision whether the active oxidant is a CuIII or a CuIV complex. Kinetic analysis of pulse radiolysis measurements coupled with DFT calculations point out that CuIII(CO3)n3−2n complexes are the active intermediates in the electrolysis of CuII(CO3)n2−2n solution. The results enable the evaluation of E°[(CuIII/II(CO3)n)aq]≈1.42 V versus NHE at pH 8.4. This redox potential is in accord with the electrochemical report. As opposed to literature suggestions for water oxidation, the present results rule out single‐electron transfer from CuIII(CO3)n3−2n to yield hydroxyl radicals. Significant charge transfer from the coordinated carbonate to CuIII results in the formation of C2O62− by means of a second‐order reaction of CuIII(CO3)n3−2n. The results point out that carbonate stabilizes transition‐metal cations at high oxidation states, not...
Inorganica Chimica Acta, 2017
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service... more This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Homogeneous and Heterogeneous Electrocatalytic Reduction of Halo-Organic Compounds by (Ni II L i) 2+ (L i = tetraaza-macrocyclic ligand) in Aqueous Solutions.
Journal of Coordination Chemistry, 2016
Abstract The kinetics and mechanisms of the oxidation of and of by the biological relevant radica... more Abstract The kinetics and mechanisms of the oxidation of and of by the biological relevant radicals and were studied. The rate constants of the oxidations by both radicals are faster for the complexes than for the complexes, though the redox potentials predict the reverse order of reactivity. Surprisingly, the results point out that these two radicals react via different mechanisms. Thus, the increase in the concentration of the ligands decreases the rate constants of the oxidations by , whereas it increases the rate constants of the oxidation by . These results point out that these radicals behave differently though both are inner-sphere oxidants. The plausible mechanisms of reaction of these radicals are discussed.
European Journal of Inorganic Chemistry, 2016
Methyl radicals react with BH4– to form BH3·–/BH4· (k ≈ 5 × 103 M–1 s–1. BH3·–/BH4· reacts with N... more Methyl radicals react with BH4– to form BH3·–/BH4· (k ≈ 5 × 103 M–1 s–1. BH3·–/BH4· reacts with N2O to form OH· radicals, which react with (CH3)2SO to form methyl radicals and thus initiate a chain oxidation process. It is suggested that analogous reactions can be initiated by the reaction of OH· radicals with other organic substrates. Thus, BH4– promotes oxidation processes.
Chemistry – A European Journal, 2015
Characterization of the thin films consisting of an amphiphilic fulleropyrrolidine and a novel wa... more Characterization of the thin films consisting of an amphiphilic fulleropyrrolidine and a novel water soluble porphyrin using Langmuir-ShA¤fer (LS) was investigated. The characterization of the LS films by UV-Vis spectroscopy revealed that the UV region was dominated by optical absorptions of the C60 subunits, while the porphyrin absorptions were very weak in this region. The use of polarized light suggested the existence of a preferential direction of macrocycle rings with an edge-on arrangement with respect to the substrate surface. The films deposited onto ITO substrates in which the floating films were transferred onto the ITO electrodes by the LS method at several surface pressures were also investigated.
Chemcatchem, Aug 10, 2016
Methyl radicals react with platinum nanoparticles (NPs) suspended in aqueous solutions to form (P... more Methyl radicals react with platinum nanoparticles (NPs) suspended in aqueous solutions to form (Pt 0-NPs)-(CH 3) n as a stable major product. Hydrogen gas treatment of the Pt 0-NPs affects the composition of the products and the surface reactions. The results clearly point out that pretreatment of Pt 0-NPs and (Pt 0-NPs)-(CH 3) n with H 2 considerably affects their reactions with methyl radicals. The implications of the results on catalytic processes are discussed.
Inorganic Chemistry
Conjugated arrays composed of corrole macrocycles are increasingly more common, but their chemist... more Conjugated arrays composed of corrole macrocycles are increasingly more common, but their chemistry still lags behind that of their porphyrin counterparts. Here, we report on the insertion of iron(III) into a β,β-fused corrole dimer and on the electronic effects that this redox active metal center has on the already rich coordination chemistry of [H 3 tpfc] COT, where COT = cyclo-octatetraene and tpfc = tris(pentafluorophenyl)corrole. Synthetic manipulations were performed for the isolation and full characterization of both the 5-coordinate [Fe III tpfc(py)] 2 COT and 6-coordinate [Fe III tpfc(py) 2 ] 2 COT, with one and two axial pyridine ligands per metal, respectively. X-Ray crystallography reveals a dome-shaped structure for [Fe III tpfc(py)] 2 COT and a perfectly planar geometry which (surprisingly at first) is also characterized by shorter Fe−N (corrole) and Fe−N (pyridine) distances. Computational investigations clarify that the structural phenomena are due to a change in the iron(III) spin state from intermediate (S = 3/2) to low (S = 1/2), and that both the 5-and 6-coordinated complexes are enthalpically favored. Yet, in contrast to iron(III) porphyrins, the formation enthalpy for the coordination of the first pyridine to Fe(III) corrole is more negative than that of the second pyridine coordination. Possible interactions between the two corrole subunits and the chelated iron ions were examined by UV−Vis spectroscopy, electrochemical techniques, and density functional theory (DFT). The large differences in the electronic spectra of the dimer relative to the monomer are concluded to be due to a reduced electronic gap, owing to the extensive electron delocalization through the fusing bridge. A cathodic sweep for the dimer discloses two redox processes, separated by 230 mV. The DFT self-consistent charge density for the neutral and cationic states (1-and 2-electron oxidized) reveals that the holes are localized on the macrocycle. A different picture emerges from the reduction process, where both the electrochemistry and the calculated charge density point toward two consecutive electron transfers with similar energetics, indicative of very weak electron communication between the two redox active iron(III) sites. The binuclear complex was determined to be a much better catalyst for the electrochemical hydrogen evolution reaction (HER) than the analogous mononuclear corrole.
Chemistry – A European Journal
Journal of Inorganic Biochemistry
Free Radical Biology and Medicine, 2021
The mechanism of reaction of DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) with... more The mechanism of reaction of DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) with ·CH3, CH3O2· and ·OH radicals were studied. The radicals were formed in situ radiolytically. The methyl radicals react orders of magnitude slower with DOTA and with MIII(DOTA)- than the hydroxyl radicals. The various final products were identified and mechanisms for their formation are proposed. CH3O2· radicals do not react, or react too slowly to be observed, with DOTA and with MIII(DOTA)- as long as the central cation is not oxidized by the peroxyl radical. The results imply that synthesis of the MIII(DOTA)-(MIII = radioisotope) complexes in a water-organic solvent (ethanol or 2-propanol or acetonitrile) mixture is not only kinetically desired but the so formed complex also decreases the radiolytic decomposition of DOTA.
Inorganica Chimica Acta, 2020
Abstract The reactions of the radicals R, R = CH3 or CH2OH, with the complex CuII(ntp)(H2O) were ... more Abstract The reactions of the radicals R, R = CH3 or CH2OH, with the complex CuII(ntp)(H2O) were studied. The kinetics of formation of the transient complexes (ntp)CuIII-R fit pseudo first order rate laws. The mechanism of decomposition of the transient complex (ntp)CuIII-CH3 at pH ≥ 7 involves homolysis of the CuIII-C bond. However, at pH
European Journal of Inorganic Chemistry, 2021
Advanced oxidation technologies often use peroxymonosulfate in the presence of CoIIaq. It is comm... more Advanced oxidation technologies often use peroxymonosulfate in the presence of CoIIaq. It is commonly assumed that the reaction of Co(H2O)62+ with HSO5− yields CoIIIaq and SO4.−. DFT results point out that first CoII(SO5)(H2O)2 is formed. The homolysis of CoII(SO5)(H2O)2 to yield (H2O)CoII(SO5)OH.+SO4.−, is exothermic but has a large activation energy. However the cobalt is not oxidized in this reaction. CoII(SO5)(H2O)2 reacts with a second HSO5− to form CoII(SO5)2(H2O)2− that decomposes via disproportionation of the monoperoxysulfate ions without oxidation of the central cobalt ion. Surprisingly even in the presence of ligands, L, that stabilize CoIII, i. e., pyrophosphate; tri‐polyphosphate and ATP, the experimentally observed reaction mechanism involves the formation of LCoII‐OOSO3aq which then reacts with another HSO5− to form LCoII‐(OOSO32−)2. The latter complex decomposes via disproportionation of the monoperoxysulfate ligands followed by oxidation of the central cobalt cation...
Chemistry – A European Journal, 2021
Two new aqueous UIV complexes were synthesized by the interaction between the tetravalent uranium... more Two new aqueous UIV complexes were synthesized by the interaction between the tetravalent uranium cation and the (1,4,7,10‐Tetraazacyclododecane‐1,4,7,10‐tetra(methylene phosphonic acid) (DOTP) macrocyclic ligand. Two distinct homonuclear complexes were identified; the first was characterized by X‐ray crystallography as a unique “out‐of‐cage”, [U(DOTPH6)2] complex, in which the UIV cation is octa‐coordinated to 4 phosphonic arms from each ligand in a square anti‐prism geometry, with a C4 symmetry. The second is the “in‐cage” [U(DOTPH4)] complex, in which the tetravalent cation is located between the macrocycle O4 and N4 planes. With the help of UV‐Vis absorption, 1H/31P NMR, ATR‐IR, and MALDI‐TOFMS analytical techniques, the chemical interchange between both species is presented. It is shown that the one‐way transition is governed by the formation of a multiple number of soluble oligomeric species consisting of varied stoichiometric ratios of both characterized homonuclear complexes.
ChemPhysChem, 2020
Supporting information for this article is given via a link at the end of the document.
Free Radical Biology and Medicine, 2021
Methyl radicals play key roles in various chemical and biological processes. Mechanistic studies ... more Methyl radicals play key roles in various chemical and biological processes. Mechanistic studies of methyl radicals with their precursor, Dimethyl Sulfoxide (DMSO), were extensively studied. Though the involved mechanisms seemed to be clarified, essentially none of the studies have been performed at conditions relevant to both biological and catalytic systems, i.e. low steady state radical concentrations. A chain-like reaction, as an inverse function of the radicals concentrations ([•CH3]ss), increases the methyl radical yields. The nature of the additional products obtained differs from those commonly observed. Furthermore it is shown that methyl radicals abstract a methyl group from DMSO to yield ethane. Herein we report a novel mechanism relevant mainly at low steady state radical concentrations, which may change the understanding of certain reaction routes present in both biological systems and catalytic chemical systems. Thus the results point out that mechanistic studies have to be carried out at dose rates forming radicals at analogous concentrations to those present in the process of interest.
Chemistry – A European Journal, 2020
The 1,4,7,10‐tetrazacyclodecane‐1,4,7,10‐tetraacetic acid (DOTA) aqueous complex of UIV with H2O,... more The 1,4,7,10‐tetrazacyclodecane‐1,4,7,10‐tetraacetic acid (DOTA) aqueous complex of UIV with H2O, OH−, and F− as axial ligands was studied by using UV/Vis spectrophotometry, ESI‐MS, NMR spectroscopy, X‐ray crystallography, and electrochemistry. The UIV–DOTA complex with either water or fluoride as axial ligands was found to be inert to oxidation by molecular oxygen, whereas the complex with hydroxide as an axial ligand slowly hydrolyzed and was oxidized by dioxygen to a diuranate precipitate. The combined data set acquired shows that, although axial substitution of fluoride and hydroxide ligands instead of water does not seem to significantly change the aqueous DOTA complex structure, it has an important effect on the electronic configuration of the complex. The UIV/UIII redox couple was found to be quasi‐reversible for the complex with both axially bonded H2O and hydroxide, but irreversible for the complex with axially bonded fluoride. Intriguingly, binding of the axial fluoride re...
Journal of Coordination Chemistry, 2019
Abstract The reactions of methyl radicals with MII-(ntp)(H2O)2 complexes were studied. The format... more Abstract The reactions of methyl radicals with MII-(ntp)(H2O)2 complexes were studied. The formation of an unstable intermediate (ntp)(H2O)MIII-CH3 is observed. This reaction is an equilibrium process, i.e. the MIII-C bond decomposes via homolysis. The (ntp)(H2O)MIII-CH3 complexes isomerize to a more stable form. The results compared to those obtained in analogous reactions of the MII-(nta)(H2O)2 complexes were shown to be similar with one exception – for the nta complexes no isomerization process is observed. Graphical Abstract
Journal of Coordination Chemistry, 2018
The reaction kinetics of eight amino-carboxylate complexes of Fe(III) and Mn(II) with carbonate r... more The reaction kinetics of eight amino-carboxylate complexes of Fe(III) and Mn(II) with carbonate radical anion were studied using the pulse radiolysis method and UV-vis spectroscopy. Difference spectra revealed the formation of Fe(IV) and Mn(III) after reaction with CO 3 •-. Spectral measurements revealed the first step to be the coordination of carbonate to the metal center. All of these led to the conclusion that the role of coordinated carbonate is essential to the electron transfer process by carbonate radical anion.
Journal of Coordination Chemistry, 2018
During an effort to synthesize the trans-III-copper(II) complex with 1,4,8,11-tetramethyl-pyropho... more During an effort to synthesize the trans-III-copper(II) complex with 1,4,8,11-tetramethyl-pyrophosphonate-1,4,8,11-tetra-aza-cyclo-tetradecane, using only perchlorate salts, it was noted that the perchlorate is reduced to chloride. Analysis of the reactions leading to this surprising result points out that Cu(H 2 O) 4 2+ catalyzes the reduction of perchlorate by H 2 and by CH 2 O. These reactions are slow at room temperature and ambient pressures. A plausible mechanism, supported by DFT calculations, is proposed pointing out that the role of CuH + under mild conditions cannot be ignored.
Chemistry – A European Journal, 2017
Recently it was reported that copper bicarbonate/carbonate complexes are good electro‐catalysts f... more Recently it was reported that copper bicarbonate/carbonate complexes are good electro‐catalysts for water oxidation. However, the results did not enable a decision whether the active oxidant is a CuIII or a CuIV complex. Kinetic analysis of pulse radiolysis measurements coupled with DFT calculations point out that CuIII(CO3)n3−2n complexes are the active intermediates in the electrolysis of CuII(CO3)n2−2n solution. The results enable the evaluation of E°[(CuIII/II(CO3)n)aq]≈1.42 V versus NHE at pH 8.4. This redox potential is in accord with the electrochemical report. As opposed to literature suggestions for water oxidation, the present results rule out single‐electron transfer from CuIII(CO3)n3−2n to yield hydroxyl radicals. Significant charge transfer from the coordinated carbonate to CuIII results in the formation of C2O62− by means of a second‐order reaction of CuIII(CO3)n3−2n. The results point out that carbonate stabilizes transition‐metal cations at high oxidation states, not...
Inorganica Chimica Acta, 2017
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service... more This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Homogeneous and Heterogeneous Electrocatalytic Reduction of Halo-Organic Compounds by (Ni II L i) 2+ (L i = tetraaza-macrocyclic ligand) in Aqueous Solutions.
Journal of Coordination Chemistry, 2016
Abstract The kinetics and mechanisms of the oxidation of and of by the biological relevant radica... more Abstract The kinetics and mechanisms of the oxidation of and of by the biological relevant radicals and were studied. The rate constants of the oxidations by both radicals are faster for the complexes than for the complexes, though the redox potentials predict the reverse order of reactivity. Surprisingly, the results point out that these two radicals react via different mechanisms. Thus, the increase in the concentration of the ligands decreases the rate constants of the oxidations by , whereas it increases the rate constants of the oxidation by . These results point out that these radicals behave differently though both are inner-sphere oxidants. The plausible mechanisms of reaction of these radicals are discussed.
European Journal of Inorganic Chemistry, 2016
Methyl radicals react with BH4– to form BH3·–/BH4· (k ≈ 5 × 103 M–1 s–1. BH3·–/BH4· reacts with N... more Methyl radicals react with BH4– to form BH3·–/BH4· (k ≈ 5 × 103 M–1 s–1. BH3·–/BH4· reacts with N2O to form OH· radicals, which react with (CH3)2SO to form methyl radicals and thus initiate a chain oxidation process. It is suggested that analogous reactions can be initiated by the reaction of OH· radicals with other organic substrates. Thus, BH4– promotes oxidation processes.
Chemistry – A European Journal, 2015