Ligand effects upon the reactions of Ni(II) with sodium tetrahydroborate: Ni(I) complexes of bipyridyl and 1,10-phenanthroline

1977 ◽  
Vol 55 (23) ◽  
pp. 4048-4055 ◽  
Author(s):  
David G. Holah ◽  
Alan N. Hughes ◽  
Benjamin C. Hui
Keyword(s):  
Electron Transfer ◽  
New Species ◽  
Sodium Tetrahydroborate ◽  
Outer Sphere ◽  
Donor Ligands ◽  
Rapid Reduction ◽  
Electron Transfer Mechanism ◽  
Ligand Effects ◽  
Coordination Sites ◽  
Citrate Reduction

The reactions between NaBH4 and Ni(II) have been studied in the presence of a variety of ligands in an effort to determine (a) the conditions under which reduction occurs, (b) the extent of the reduction (e.g. to Ni(I), Ni(0) complexes, or to Ni metal or boride), and (c) whether intermediate Ni complexes can be isolated.With ligands having no π-bonding capabilities (NH3, ethylenediamine, edta, citrate), reduction depends upon the Ni:ligand ratio and, in the presence of an excess of the ligand, reduction of Ni(II) is very slow. When vacant coordination sites exist on the metal through dissociation of, for example, Ni(NH3)62+, allowing for the interaction of the BH4 group with the metal, then rapid reduction to the metal (or boride) takes place.With the π-bonding N-donor ligands 1,10-phenanthroline (phen) and 2,2′-bipyridyl (bipy) reduction of the stable ML32+ complexes probably occurs via an outer-sphere electron transfer mechanism but, in these cases, new species of the type NiL2X (L = phen, bipy; X = BH4, PF6, BPh4), which formally contain Ni(I), have been isolated.

Cycloaddition of CO2 with epoxides and esterification reactions using the porous redox catalyst Co-POM@MIL-101(Cr)

2019 ◽  
Vol 43 (39) ◽  
pp. 15585-15595 ◽  
Author(s):  
Afsaneh Marandi ◽  
Mehrnaz Bahadori ◽  
Shahram Tangestaninejad ◽  
Majid Moghadam ◽  
Valiollah Mirkhani ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Acetic Acid ◽  
Catalytic Activity ◽  
Outer Sphere ◽  
Transfer Mechanism ◽  
Solvent Free ◽  
Electron Transfer Mechanism ◽  
Redox Catalyst ◽  
Redox Pair ◽  
Esterification Reactions

The catalytic activity of the Co-POM@MIL-101(Cr) composite in solvent-free cycloaddition of CO2 to epoxides and esterification of acetic acid with alcohols is due to an outer-sphere electron transfer mechanism using the Co(iii)/Co(ii) redox pair.

Kinetics of N-substituted phenothiazines and N-substituted phenoxazines oxidation catalyzed by fungal laccases

2009 ◽  
Vol 4 (1) ◽  
pp. 62-67 ◽  
Author(s):  
Lidija Tetianec ◽  
Juozas Kulys
Keyword(s):  
Electron Transfer ◽  
Redox Potential ◽  
Reorganization Energy ◽  
Outer Sphere ◽  
Initial Reaction Rate ◽  
Initial Reaction ◽  
Type I ◽  
Electron Transfer Mechanism ◽  
Recombinant Laccase ◽  
Kinetics Of

AbstractLaccase-catalyzed oxidation of N-substituted phenothiazines and N-substituted phenoxazines was investigated at pH 5.5 and 25°C. The recombinant laccase from Polyporus pinsitus (rPpL) and the laccase from Myceliophthora thermophila (rMtL) were used. The dependence of initial reaction rate on substrate concentration was analyzed by applying the laccase action scheme in which the laccase native intermediate (NI) reacts with a substrate forming reduced enzyme. The reduced laccase produces peroxide intermediate (PI) which in turn decays to the NI. The calculated constant (kox) values of the PI formation are (6.1±3.1)×105 M−1s−1 for rPpL and (2.5±0.9)×104 M−1s−1 for rMtL. The bimolecular constants of the reaction of the native intermediate with electron donor (kred) vary in the interval from 2.2×105 to 2.1×107 M−1s−1 for rPpL and from 1.3×102 to 1.8×105 M-1s−1 for rMtL. The larger reactivity of rPpL in comparison to rMtL is associated with the higher redox potential of type I Cu of rPpL. The variation of kred values for both laccases correlates with the change of the redox potential of substrates. Following outer sphere (Marcus) electron transfer mechanism the calculated activationless electron transfer rate and the apparent reorganization energy are 5.0×107 M−1s−1 and 0.29 eV, respectively.

scholarly journals Analyzing mechanisms in Co(i) redox catalysis using a pattern recognition platform

2021 ◽  
Vol 12 (13) ◽  
pp. 4771-4778
Author(s):  
Tianhua Tang ◽  
Christopher Sandford ◽  
Shelley D. Minteer ◽  
Matthew S. Sigman
Keyword(s):  
Pattern Recognition ◽  
Electron Transfer ◽  
Linear Regression ◽  
Electrochemical Reduction ◽  
Kinetic Studies ◽  
Outer Sphere ◽  
Cobalt Complexes ◽  
Transfer Mechanism ◽  
Redox Catalysis ◽  
Electron Transfer Mechanism

Through kinetic studies combining electroanalytical techniques with multivariable linear-regression (MLR) analysis, a pattern recognition platform is established to determine the electron-transfer mechanism (inner-sphere or outer-sphere) of an electrochemical reduction of benzyl bromides, mediated by different cobalt complexes.

scholarly journals Selective, High-Temperature O2 Adsorption in Chemically Reduced, Redox-Active Iron-Pyrazolate Metal–Organic Frameworks

2020 ◽  
Author(s):  
Adam Jaffe ◽  
Michael Ziebel ◽  
David M. Halat ◽  
Naomi Biggins ◽  
Ryan Murphy ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Adsorption Mechanism ◽  
Selective Adsorption ◽  
Metal Organic Framework ◽  
Outer Sphere ◽  
Electron Transfer Mechanism ◽  
X Ray ◽  
Metal Organic ◽  
Outer Sphere Electron Transfer ◽  
Organic Framework

Developing O<sub>2</sub>-selective adsorbents that can produce high-purity oxygen from air remains a significant challenge. Here, we show that chemically reduced metal–organic framework materials of the type A<i><sub>x</sub></i>Fe<sub>2</sub>(bdp)<sub>3</sub> (A = Na<sup>+</sup>, K<sup>+</sup>; bdp<sup>2</sup><sup>−</sup> = 1,4-benzenedipyrazolate; 0 < <i>x</i> ≤ 2), which feature coordinatively saturated iron centers, are capable of strong and selective adsorption of O<sub>2</sub> over N<sub>2</sub> at ambient (25 °C) or even elevated (200 °C) temperature. A combination of gas adsorption analysis, single-crystal X-ray diffraction, magnetic susceptibility measurements, and a range of spectroscopic methods, including <sup>23</sup>Na solid-state NMR, Mössbauer, and X-ray photoelectron spectroscopies, are employed as probes of O<sub>2</sub> uptake. Significantly, the results support a selective adsorption mechanism involving outer-sphere electron transfer from the framework to form superoxide species, which are subsequently stabilized by intercalated alkali metal cations that reside in the one-dimensional triangular pores of the structure. We further demonstrate similar O<sub>2</sub> uptake behavior to that of A<i><sub>x</sub></i>Fe<sub>2</sub>(bdp)<sub>3</sub> in an expanded-pore framework analogue and thereby gain additional insight into the O<sub>2</sub> adsorption mechanism. The chemical reduction of a robust metal–organic framework to render it capable of binding O<sub>2</sub> through such an outer-sphere electron transfer mechanism represents a promising and underexplored strategy for the design of next-generation O<sub>2</sub> adsorbents.

scholarly journals Selective, High-Temperature O2 Adsorption in Chemically Reduced, Redox-Active Iron-Pyrazolate Metal–Organic Frameworks

2019 ◽  
Author(s):  
Adam Jaffe ◽  
Michael Ziebel ◽  
David M. Halat ◽  
Naomi Biggins ◽  
Ryan Murphy ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Photoelectron Spectroscopy ◽  
Chemical Reduction ◽  
Metal Organic Framework ◽  
Outer Sphere ◽  
Electron Transfer Mechanism ◽  
X Ray ◽  
Metal Organic ◽  
Outer Sphere Electron Transfer ◽  
Organic Framework

Developing O<sub>2</sub>-selective adsorbents that can produce high-purity oxygen from air remains a significant challenge. Here, we show that the chemically reduced metal–organic framework A<i><sub>x</sub></i>Fe<sub>2</sub>(BDP)<sub>3</sub> (A = Na<sup>+</sup>, K<sup>+</sup>; BDP<sup>2</sup><sup>−</sup> = 1,4-benzenedipyrazolate; 0 < <i>x</i> ≤ 2), which features coordinatively-saturated iron centers, is capable of strong and selective adsorption of O<sub>2</sub> over N<sub>2</sub> at ambient (25 °C) or even elevated (200 °C) temperature. Through a combination of gas adsorption measurements, single-crystal X-ray diffraction, and numerous spectroscopic probes, including <sup>23</sup>Na solid-state NMR and X-ray photoelectron spectroscopy, we demonstrate that selective O<sub>2</sub> uptake likely occurs as a result of outer-sphere electron transfer from the framework to form superoxide species, which are subsequently stabilized by intercalated alkali metal cations that reside in the one-dimensional triangular pores of the framework. The chemical reduction of a robust metal–organic framework to render it capable of binding O<sub>2</sub> through an outer-sphere electron transfer mechanism thus represents a promising and underexplored strategy for the design of next-generation O<sub>2</sub> adsorbents.

scholarly journals Kinetic study of surfactant cobalt (III) complexes by [Fe(CN)6 4-]: Outer-Sphere Electron-Transfer in Ionic liquids and Liposome Vesicle

2020 ◽  
pp. 300-317
Author(s):  
Nagaraj Karuppiah ◽  
◽  
Pakkirisamy Pakkirisamy ◽  
Gunasekaran Gladwin ◽  
◽  
...  
Keyword(s):  
Phase Transition ◽  
Electron Transfer ◽  
Ionic Liquids ◽  
Transition Temperature ◽  
Transition State ◽  
Phase Transition Temperature ◽  
Outer Sphere ◽  
Complex Ions ◽  
Electron Transfer Mechanism ◽  
Outer Sphere Electron Transfer

UV-Vis., absorption spectroscopy are used to monitor the electron transfer reaction between the surfactant cobalt(III) complexes, cis-[Co(ip)2(C14H29NH2)2]3+, cis-[Co(dpq)2(C14H29NH2)2]3+ and cis-[Co(dpqc)2(C14H29NH2)2]3+ (ip = imidazo[4,5-f][1,10]phenanthroline, dpq = dipyrido[3,2-d:2’-3’-f]quinoxaline, dpqc = dipyrido[3,2-a:2’,4’-c](6,7,8,9-tetrahydro)phenazine, C14H29NH2=Tetradecylamine) and [Fe(CN)6]4- ion in liposome vesicles (DPPC) and ionic liquids ((BMIM)Br) were investigated at different temperatures under pseudo first order conditions using an excess of the reductant. The reactions were found to be second order and the electron transfer is postulated as outer-sphere. The rate constant for the electron transfer reactions were found to increase with increasing concentrations of ionic liquids. The effects of hydrophobicity of the long aliphatic double chains of these surfactant complex ions into liposome vesicles on these reactions have also been studied. Below the phase transition temperature of DPPC, the rate decreased with increasing concentration of DPPC, while above the phase transition temperature the rate increased with increasing concentration of DPPC. Kinetic data and activation parameters are interpreted in terms of an outer-sphere electron transfer mechanism. In all these media the S# values are found to be negative in direction in all the concentrations of complexes used indicative of more ordered structure of the transition state. This is consistent with a model in which the surfactant cobalt(III) complexes and Fe(CN)64- ions bind to the DPPC in the transition state. Thus, the results have been explained based on the self-aggregation, hydrophobic effect, and the reactants with opposite charge.

scholarly journals Single-electron reduction of quinone and nitroaromatic xenobiotics by recombinant rat neuronal nitric oxide synthase.

2013 ◽  
Vol 60 (2) ◽  
Author(s):  
Žilvinas Anusevičius ◽  
Henrikas Nivinskas ◽  
Jonas Šarlauskas ◽  
Marie-Agnes Sari ◽  
Jean-Luc Boucher ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Electron Transfer ◽  
Nitric Oxide Synthase ◽  
Neuronal Nitric Oxide Synthase ◽  
Outer Sphere ◽  
Transfer Mechanism ◽  
Single Electron ◽  
Electron Transfer Mechanism ◽  
Electron Reduction ◽  
Oxide Synthase

We examined the kinetics of single-electron reduction of a large number of structurally diverse quinones and nitroaromatic compounds, including a number of antitumour and antiparasitic drugs, and nitroaromatic explosives by recombinant rat neuronal nitric oxide synthase (nNOS, EC 1.14.13.39), aiming to characterize the role of nNOS in the oxidative stress-type cytotoxicity of the above compounds. The steady-state second-order rate constants (kcat/Km) of reduction of the quinones and nitroaromatics varied from 10² M⁻¹s⁻¹ to 10⁶ M⁻¹s⁻¹, and increased with an increase in their single-electron reduction potentials (E¹₇). The presence of Ca²⁺/calmodulin enhanced the reactivity of nNOS. These reactions were consistent with an 'outer sphere' electron-transfer mechanism, considering the FMNH∙/FMNH₂ couple of nNOS as the most reactive reduced enzyme form. An analysis of the reactions of nNOS within the 'outer sphere' electron-transfer mechanism gave the approximate values of the distance of electron transfer, 0.39-0.47 nm, which are consistent with the crystal structure of the reductase domain of nNOS. On the other hand, at low oxygen concentrations ([O₂] = 40-50 μM), nNOS performs a net two-electron reduction of quinones and nitroaromatics. This implies that NOS may in part be responsible for the bioreductive alkylation by two-electron reduced forms of antitumour aziridinyl-substituted quinones under a modest hypoxia.

scholarly journals Selective, High-Temperature O2 Adsorption in Chemically Reduced, Redox-Active Iron-Pyrazolate Metal–Organic Frameworks

2019 ◽  
Author(s):  
Adam Jaffe ◽  
Michael Ziebel ◽  
David M. Halat ◽  
Naomi Biggins ◽  
Ryan Murphy ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Photoelectron Spectroscopy ◽  
Chemical Reduction ◽  
Metal Organic Framework ◽  
Outer Sphere ◽  
Electron Transfer Mechanism ◽  
X Ray ◽  
Metal Organic ◽  
Outer Sphere Electron Transfer ◽  
Organic Framework

Developing O<sub>2</sub>-selective adsorbents that can produce high-purity oxygen from air remains a significant challenge. Here, we show that the chemically reduced metal–organic framework A<i><sub>x</sub></i>Fe<sub>2</sub>(BDP)<sub>3</sub> (A = Na<sup>+</sup>, K<sup>+</sup>; BDP<sup>2</sup><sup>−</sup> = 1,4-benzenedipyrazolate; 0 < <i>x</i> ≤ 2), which features coordinatively-saturated iron centers, is capable of strong and selective adsorption of O<sub>2</sub> over N<sub>2</sub> at ambient (25 °C) or even elevated (200 °C) temperature. Through a combination of gas adsorption measurements, single-crystal X-ray diffraction, and numerous spectroscopic probes, including <sup>23</sup>Na solid-state NMR and X-ray photoelectron spectroscopy, we demonstrate that selective O<sub>2</sub> uptake likely occurs as a result of outer-sphere electron transfer from the framework to form superoxide species, which are subsequently stabilized by intercalated alkali metal cations that reside in the one-dimensional triangular pores of the framework. The chemical reduction of a robust metal–organic framework to render it capable of binding O<sub>2</sub> through an outer-sphere electron transfer mechanism thus represents a promising and underexplored strategy for the design of next-generation O<sub>2</sub> adsorbents.

scholarly journals Selective, High-Temperature O2 Adsorption in Chemically Reduced, Redox-Active Iron-Pyrazolate Metal–Organic Frameworks

2020 ◽  
Author(s):  
Adam Jaffe ◽  
Michael Ziebel ◽  
David M. Halat ◽  
Naomi Biggins ◽  
Ryan Murphy ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Adsorption Mechanism ◽  
Selective Adsorption ◽  
Metal Organic Framework ◽  
Outer Sphere ◽  
Electron Transfer Mechanism ◽  
X Ray ◽  
Metal Organic ◽  
Outer Sphere Electron Transfer ◽  
Organic Framework

Developing O<sub>2</sub>-selective adsorbents that can produce high-purity oxygen from air remains a significant challenge. Here, we show that chemically reduced metal–organic framework materials of the type A<i><sub>x</sub></i>Fe<sub>2</sub>(bdp)<sub>3</sub> (A = Na<sup>+</sup>, K<sup>+</sup>; bdp<sup>2</sup><sup>−</sup> = 1,4-benzenedipyrazolate; 0 < <i>x</i> ≤ 2), which feature coordinatively saturated iron centers, are capable of strong and selective adsorption of O<sub>2</sub> over N<sub>2</sub> at ambient (25 °C) or even elevated (200 °C) temperature. A combination of gas adsorption analysis, single-crystal X-ray diffraction, magnetic susceptibility measurements, and a range of spectroscopic methods, including <sup>23</sup>Na solid-state NMR, Mössbauer, and X-ray photoelectron spectroscopies, are employed as probes of O<sub>2</sub> uptake. Significantly, the results support a selective adsorption mechanism involving outer-sphere electron transfer from the framework to form superoxide species, which are subsequently stabilized by intercalated alkali metal cations that reside in the one-dimensional triangular pores of the structure. We further demonstrate similar O<sub>2</sub> uptake behavior to that of A<i><sub>x</sub></i>Fe<sub>2</sub>(bdp)<sub>3</sub> in an expanded-pore framework analogue and thereby gain additional insight into the O<sub>2</sub> adsorption mechanism. The chemical reduction of a robust metal–organic framework to render it capable of binding O<sub>2</sub> through such an outer-sphere electron transfer mechanism represents a promising and underexplored strategy for the design of next-generation O<sub>2</sub> adsorbents.

scholarly journals Selective, High-Temperature O2 Adsorption in Chemically Reduced, Redox-Active Iron-Pyrazolate Metal–Organic Frameworks

2020 ◽  
Author(s):  
Adam Jaffe ◽  
Michael Ziebel ◽  
David M. Halat ◽  
Naomi Biggins ◽  
Ryan Murphy ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Adsorption Mechanism ◽  
Selective Adsorption ◽  
Metal Organic Framework ◽  
Outer Sphere ◽  
Electron Transfer Mechanism ◽  
X Ray ◽  
Metal Organic ◽  
Outer Sphere Electron Transfer ◽  
Organic Framework

Developing O<sub>2</sub>-selective adsorbents that can produce high-purity oxygen from air remains a significant challenge. Here, we show that chemically reduced metal–organic framework materials of the type A<i><sub>x</sub></i>Fe<sub>2</sub>(bdp)<sub>3</sub> (A = Na<sup>+</sup>, K<sup>+</sup>; bdp<sup>2</sup><sup>−</sup> = 1,4-benzenedipyrazolate; 0 < <i>x</i> ≤ 2), which feature coordinatively saturated iron centers, are capable of strong and selective adsorption of O<sub>2</sub> over N<sub>2</sub> at ambient (25 °C) or even elevated (200 °C) temperature. A combination of gas adsorption analysis, single-crystal X-ray diffraction, magnetic susceptibility measurements, and a range of spectroscopic methods, including <sup>23</sup>Na solid-state NMR, Mössbauer, and X-ray photoelectron spectroscopies, are employed as probes of O<sub>2</sub> uptake. Significantly, the results support a selective adsorption mechanism involving outer-sphere electron transfer from the framework to form superoxide species, which are subsequently stabilized by intercalated alkali metal cations that reside in the one-dimensional triangular pores of the structure. We further demonstrate similar O<sub>2</sub> uptake behavior to that of A<i><sub>x</sub></i>Fe<sub>2</sub>(bdp)<sub>3</sub> in an expanded-pore framework analogue and thereby gain additional insight into the O<sub>2</sub> adsorption mechanism. The chemical reduction of a robust metal–organic framework to render it capable of binding O<sub>2</sub> through such an outer-sphere electron transfer mechanism represents a promising and underexplored strategy for the design of next-generation O<sub>2</sub> adsorbents.

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