Environmental Mineralogy

Mukherjee, Swapna

doi:10.1007/978-94-007-1162-4_18

Cited by 6 publications

(9 citation statements)

References 4 publications

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“…Notably, upon one-electron reduction, the remaining unpaired electron gets delocalized over the two ligands, as is clear from the spin density plot in Figure . Similar observations were reported for related systems. ,− , This result is consistent with the experimentally observed ligand centered EPR data of complex [ 2 ] − . Analysis of the molecular orbitals reveals that both the occupied and unoccupied MOs of the complexes [ 1 ] 2+ and 2 are mainly ligand-based, with a small contribution from the metal center in all cases (S7, S8).…”

Section: Resultssupporting

confidence: 92%

“…Moreover, I p for the oxidative redox couple (at 0.34 V) is significantly (∼2.5 times) higher than that of the single-electron reductive wave. Similar Ni II -complexes reported by others are also known to exhibit such type of single step two-electron redox events. , On the basis of our experimental results coupled with the available literature data, ,, we assign the first anodic response at 0.34 V as a two-electron process. Notably, the simpler analogue of complex 2 , the one without the additional aryl amine arm shows a one-electron reversible oxidation at −0.07 V and a one-electron reversible reduction at −1.21 V along with two additional quasi reversible responses at 0.21 and −1.89 V respectively…”

Section: Resultssupporting

confidence: 87%

“…This is in good agreement with all experimental data described above. Broken symmetry density functional calculations (BS, S = 0), clearly shows that the two coordinated ligands are open shell, π-radical monoanions (L •– ), as shown computationally for analogous systems. ,− , The selected bond parameters along with the spin density analysis reveal the iminosemiquinone (L •– ) oxidation state of the coordinated ligands with the valence configuration of [Ni II (L •– ) 2 ]. One of these two ligands remains in the spin-up manifold, while the second one is in the spin-down manifold, yielding the observed antiferromagnetically coupled diamagnetic singlet ( S = 0) ground state.…”

Section: Resultsmentioning

confidence: 87%

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Deprotonation Induced Ligand Oxidation in a Ni^II Complex of a Redox Noninnocent N¹-(2-Aminophenyl)benzene-1,2-diamine and Its Use in Catalytic Alcohol Oxidation

et al. 2016

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Two nickel(II)-complexes, [Ni(II)(H3L)2](ClO4)2 ([1](ClO4)2) and [Ni(II)(HL)2] (2), containing the redox-active tridentate ligand N(1)-(2-aminophenyl)benzene-1,2-diamine (H3L) have been synthesized. Complex [1](ClO4)2 is octahedral containing two neutral H3L ligands in a facial coordination mode, whereas complex 2 is a singlet diradical species with approximately planar configuration at the tetracoordinate metal atom with two pendant NH2 side arms from each of the coordinated ligands. Both complexes are found to be chemically interconvertible; complex [1](2+) gets converted to complex 2 when exposed to base and oxygen via simultaneous deprotonation and oxidation of the coordinated ligands. Molecular and electronic structures of the isolated complexes are scrutinized thoroughly by various spectroscopic techniques, single crystal X-ray crystallography, and density functional theory. The observed dissociation of a ligand arm upon oxidation of the ligand was exploited to bring about catalytic alcohol oxidation using coordinatively saturated complex [1](ClO4)2 as a catalyst precursor. Both the complexes [1](ClO4)2and 2 were tested for catalytic oxidation of both primary and secondary alcohols.

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Section: Resultssupporting

confidence: 92%

Section: Resultssupporting

confidence: 87%

Section: Resultsmentioning

confidence: 87%

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Deprotonation Induced Ligand Oxidation in a Ni^II Complex of a Redox Noninnocent N¹-(2-Aminophenyl)benzene-1,2-diamine and Its Use in Catalytic Alcohol Oxidation

et al. 2016

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“…As a part of our interest in metal-coordinated radicals, we have synthesized a new potentially tridentate o -aminophenol ligand which carries an additional redox-active azo group, 2-(2-phenylazo)-anilino-4,6-di- tert -butylphenol H 2 (L AP ) (Figure ). This ligand is unique in the sense that electron-rich o -amidophenolate(2−) unit will donate electron-density to the metal-ion but a π-accepting azo group is expected to withdraw electron-density to impart highly delocalized metal–ligand interaction.…”

Section: Introductionmentioning

confidence: 99%

Neutral, Cationic, and Anionic Low-Spin Iron(III) Complexes Stabilized by Amidophenolate and Iminobenzosemiquinonate Radical inN,N,OLigands

et al. 2013

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A brownish-black complex [Fe(III)(L)2] (1) (S = 0), supported by two tridentate redox-active azo-appended o-amidophenolates [H2L = 2-(2-phenylazo)-anilino-4,6-di-tert-butylphenol], has been synthesized and structurally characterized. In CH2Cl2 1 displays two oxidative and two reductive 1e(-) redox processes at E1/2 values of 0.48 and 1.06 V and -0.42 and -1.48 V vs SCE, respectively. The one-electron oxidized form [1](+) isolated as a green solid [Fe(III)(L)2][BF4] (2) (S = 1/2) has been structurally characterized. Isolation of a dark ink-blue one-electron reduced form [1](-) has also been achieved [Co(III)(η(5)-C10H15)2][Fe(III)(L)2] (3) (S = 1/2). Mössbauer spectral parameters unequivocally establish that 1 is a low-spin (LS) Fe(III) complex. Careful analysis of Mössbauer spectral data of 2 and 3 at 200 and 80 K reveal that each complex has a major LS Fe(III) and a minor LS Fe(II) component (redox isomers): [Fe(III){(L(ISQ))(-•)}2](+) and [Fe(II){(L(IBQ))(0)}{(L(ISQ))(-•)}](+) (2) and [Fe(III){(L(AP))(2-)}2](-) and [Fe(II){(L(ISQ))(-•)}{(L(AP))(2-)}](-) (3). Notably, for both at 8 K mainly the major component exists. Broken-Symmetry (BS) Density Functional Theory (DFT) calculations at the B3LYP level reveals that in 1 the unpaired electron of LS Fe(III) is strongly antiferromagnetically coupled with a π-radical of o-iminobenzosemiquinonate(1-) (L(ISQ))(-•) form of the ligand, delocalized over two ligands providing 3- charge (X-ray structure). DFT calculations reveal that the unpaired electron in 2 is due to (L(ISQ))(-•) [LS Fe(III) (SFe = 1/2) is strongly antiferromagnetically coupled to one of the (L(ISQ))(-•) radicals (Srad = 1/2)] and 3 is primarily a LS Fe(III) complex, supported by two o-amidophenolate(2-) ligands. Time-Dependent-DFT calculations shed light on the origin of UV-vis-NIR spectral absorptions for 1-3. The collective consideration of Mössbauer, variable-temperature (77-298 K) electron paramagnetic resonance (EPR), and absorption spectral behavior at 298 K, and DFT results reveals that in 2 and 3 the valence-tautomerism is operative in the temperature range 80-300 K.

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“…Acid Mine Drainage (AMD) is acidic water (pH<5.0) containing elevated concentrations of sulfate and toxic elements like As, Cd, Pb, Fe, Cu, Zn and Mn formed by the interaction of sulfide-bearing rocks and mining wastes with atmospheric oxygen and water (e.g. Mukherjee, 2011). Due to its toxicity, the extraction of AMD produced within flooded mines and its discharge to neighboring streams and rivers represents an important source of pollution for surface water and aquifers by toxic elements and a serious menace to aquatic ecosystems (e.g.…”

Section: Introductionmentioning

confidence: 99%

Temporal and spatial hydrogeochemical evolution and lead isotopic composition of a contaminated stream of Taxco, Guerrero, Mexico

et al. 2020

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Discharge of Acid Mine Drainage (AMD) produced within flooded mines is a major environmental issue in most polymetallic mining sites severely impacting nearby natural resources and producing a serious menace to the ecosystem and humans. The identification of both natural and anthropological factors influencing the bioavailability of toxic elements is relevant in revealing their behavior but also in the design of strategies for mitigating adverse effects to the environment. For these purposes, we carried out a spatial and seasonal hydrogeochemical (total and soluble contents) and a lead isotopic study of the AMD of the Xochula stream in the mining region of Taxco, Guerrero, in southern Mexico. The AMD is produced by the periodic discharge from the flooded Guerrero mine to the Xochula stream and is characterized by low to moderate pH, high sulfate, and high total and soluble metal contents. The AMD shows significant spatial but smaller temporal variations. Flow of AMD through a culvert made of concrete produces the most important chemical changes recorded regardless of the time of year significantly decreasing the electrical conductance and the concentration of total and soluble potentially toxic elements. Distribution of metals and As between dissolved and particulate-bound species is pH-controlled. Due to the short interaction time between the AMD and bedrock and the formation of coatings, lithology plays a minor role in neutralization, whereas mixing of AMD with freshwater is only significant in the less acidic segment of the stream. Neutralization of AMD entails a significant decrease of the concentration of both total and soluble metals and As and chemical speciation indicates that oxides, carbonates and sulfates are the reactive phases. The Pb isotopic composition reveals that metals derive from the Taxco ore deposit and that AMD is influenced by rocks of the Morelos and Taxco Schist formations.

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Environmental Mineralogy

Cited by 6 publications

References 4 publications

Deprotonation Induced Ligand Oxidation in a Ni^II Complex of a Redox Noninnocent N¹-(2-Aminophenyl)benzene-1,2-diamine and Its Use in Catalytic Alcohol Oxidation

Deprotonation Induced Ligand Oxidation in a Ni^II Complex of a Redox Noninnocent N¹-(2-Aminophenyl)benzene-1,2-diamine and Its Use in Catalytic Alcohol Oxidation

Neutral, Cationic, and Anionic Low-Spin Iron(III) Complexes Stabilized by Amidophenolate and Iminobenzosemiquinonate Radical inN,N,OLigands

Temporal and spatial hydrogeochemical evolution and lead isotopic composition of a contaminated stream of Taxco, Guerrero, Mexico

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Environmental Mineralogy

Cited by 6 publications

References 4 publications

Deprotonation Induced Ligand Oxidation in a NiII Complex of a Redox Noninnocent N1-(2-Aminophenyl)benzene-1,2-diamine and Its Use in Catalytic Alcohol Oxidation

Deprotonation Induced Ligand Oxidation in a NiII Complex of a Redox Noninnocent N1-(2-Aminophenyl)benzene-1,2-diamine and Its Use in Catalytic Alcohol Oxidation

Neutral, Cationic, and Anionic Low-Spin Iron(III) Complexes Stabilized by Amidophenolate and Iminobenzosemiquinonate Radical inN,N,OLigands

Temporal and spatial hydrogeochemical evolution and lead isotopic composition of a contaminated stream of Taxco, Guerrero, Mexico

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Deprotonation Induced Ligand Oxidation in a Ni^II Complex of a Redox Noninnocent N¹-(2-Aminophenyl)benzene-1,2-diamine and Its Use in Catalytic Alcohol Oxidation

Deprotonation Induced Ligand Oxidation in a Ni^II Complex of a Redox Noninnocent N¹-(2-Aminophenyl)benzene-1,2-diamine and Its Use in Catalytic Alcohol Oxidation