Tuning the Electronic Structure of Halidobis(o-imino-benzosemiquinonato)iron(III) Complexes

Chun, Hyungphil; Weyhermüller, Thomas; Bill, Eckhard; Wieghardt, Karl

doi:10.1002/1521-3773(20010702)40:13<2489::aid-anie2489>3.0.co;2-5

Cited by 110 publications

(109 citation statements)

References 15 publications

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“…The intense absorption maxima at 695 nm (ε ϭ 1.87 ϫ 10 4  Ϫ1 cm Ϫ1 ) and 884 nm (1.03 ϫ 10 4  Ϫ1 cm Ϫ1 ) were again indicative of the presence of two O,N-coordinated (L O ISQ ) 1Ϫ π-radical ligands. In an attempt to generate the exact analogue of 2, the reaction between [Co(H 2 O) 6 (5). Note that the coordinated chloride ion in 5 had to have been abstracted from chloroform.…”

Section: Complexes 4 Andmentioning

confidence: 99%

“…From the results described below we inferred that the monomers were the electroactive species. 6) Coulometric measurements established that the monomer of 2 could be reduced in a one-electron fashion at a fixed potential of Ϫ1.0 V and by another electron at Ϫ2.0 V, and oxidized by 1 e Ϫ at 0.15 V. Thus a monocation, a monoanion, and a dianion can be reversibly generated from 2 electrochemically. The dianion proved to be too sensitive for further investigation.…”

Section: Electro-and Spectroelectrochemistrymentioning

confidence: 99%

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Cobalt(II)/(III) Complexes Containingo-Iminothiobenzosemiquinonato(1−) ando-Iminobenzosemiquinonato(1−) π-Radical Ligands

Herebian

Ghosh

Chun

et al. 2002

Eur. J. Inorg. Chem.

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The coordination chemistry of 6-amino-2,4-di-tert-butylthiophenol (H[L S AP ]) and of 2-anilino-4,6-di-tert-butylphenol (H[L O AP ]) with cobalt(II) ions was investigated in the presence and absence of dioxygen. It was shown that both compounds were redox-non-innocent ligands, existing in different protonation and oxidation levels as: (i) o-aminophenolates(1−) [(L X AP ) 1− ], (ii) o-imidophenolates(2−) [(L X IP ) 2− ], and (iii) oneelectron oxidized forms o-iminobenzosemiquinonates(1−) [(L X ISQ ) 1− ], which are π-radicals (X = S, O for the sulfur or oxygen derivative). The following complexes were synthesized: [Co II (L S AP ) 2 ] 2 (1), [Co II (L S ISQ ) 2 ] 2 ·0.5n-hexane (2·0.5n-hexane), [Co III I(L S ISQ ) 2 ] (3), [Co III I(L O ISQ ) 2 ] (4), and [Co III Cl(L O ISQ ) 2 ] (5). The compounds 2·0.5n-hexane, 4, and 5 were structurally

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Section: Complexes 4 Andmentioning

confidence: 99%

Section: Electro-and Spectroelectrochemistrymentioning

confidence: 99%

Cobalt(II)/(III) Complexes Containingo-Iminothiobenzosemiquinonato(1−) ando-Iminobenzosemiquinonato(1−) π-Radical Ligands

Herebian

Ghosh

Chun

et al. 2002

Eur. J. Inorg. Chem.

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“…Four forms of o-aminothiophenol (L) and substituted o-aminothiophenol (L 1 ) that differ in their protonation and oxidation states have been established unequivocally by Wieghardt and coworkers [12][13][14], as shown in scheme 1.…”

Section: Resultsmentioning

confidence: 99%

“…This suggests that the two ligand -radical , where M ¼ Ni, Pd, and Pt, S t ¼ 0, while for [Fe III (L ISQ 1 ) 2 X] where X ¼ Cl, Br, or I, S t ¼ ½, suggesting strong antiferromagnetic coupling in all these cases [12][13][14]. Such strong antiferromagnetic coupling is also observed for the Cr(III) compounds reported by Kapre et al [22] who isolated the neutral complex…”

Section: Magnetic Momentsmentioning

confidence: 99%

“…We have synthesized a Cr (II) compound, [Cr(H 2 O)(L ISQ ) 2 ] (1), containing [12][13][14] two oiminothionebenzosemiquinonate(1À) -radicals (L ISQ ) 1À and one water as the coordinated ligands which is very different from the reported blue Cr(II) bischelate complex [Cr(L AP ) 2 ] (where (L AP ) 1À is the o-aminothiophenolate(1À)) that was synthesized by Larkworthy et al [15] in dinitrogen atmosphere. Compound 1 is 3330 M.K.…”

Section: Introductionmentioning

confidence: 99%

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Dioxygen binding and activation by a highly reactive Cr(II) compound containing S,N-donors derived from o-aminothiophenol

Koley

Sivasubramanian

Biswas

et al. 2012

Journal of Coordination Chemistry

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We report the synthesis, characterization, and reactivity of a Cr(II) complex, [Cr(H 2 O)(L ISQ ) 2 ] (1) [(L ISQ ) 1À is o-iminothionebenzosemiquinonate(1À) -radical], that is highly stable in solid state in the presence of air but undergoes spontaneous change in solution, both in the presence and absence of air. Physicochemical studies in solution show that a superoxo-Cr III species, [Cr(O 2 )(OH)(L ISQ ) 2 ] À is generated initially in DMF solution of 1 in the presence of air owing to its immediate deprotonation followed by O 2 binding to the deprotonated species. The formation of this superoxo-Cr III species is prominent and gradual in the presence of CH 3 OH, a scavenger of CrO 2þ species. This Cr(O 2 ) 2þ species in turn is converted to another highly reactive O¼Cr(IV) intermediate [O¼Cr(OH)(L ISQ ) 2 ] À which undergoes disproportionation producing an unstable O¼Cr(V) species, [O¼Cr(OH)(L ISQ ) 2 ] and a stable Cr(III) compound, [Cr(OH)(DMF)(L ISQ ) 2 ] (2). The rate of this disproportionation is enhanced in the presence of MnCl 2 , [N(n-Bu) 4 ]PF 6 and KSCN. The generated O¼Cr(IV) species interacts with DNA with complete cleavage. The O¼Cr(V) species slowly disappears from solution as revealed from EPR studies.

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Metal Coordinated Phenoxyl Radicals

Thomas

2010

Stable Radicals

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The term "phenoxyl" radical was first introduced in 1914 by Pummerer 1 to designate species involved in the oxidation of naphthols and phenanthroles. It was not until the 1960s that the existence of phenoxyls was demonstrated by Electron Paramagnetic Resonance (EPR). The term "stable" is commonly used to designate radicals such as nitroxides, trityls, and so on. Although the term "stable" had been associated with some phenoxyl radicals in 1967, 2 it must be realized that phenoxyl radicals exhibiting stabilities comparable to those of nitroxides were rather rare at this time. During the 1970s, Reichard et al . 3 demonstrated that radicals related to phenoxyls could also arise from mono-electronic oxidation of the phenolic side chain of tyrosines in some proteins, and thus could be involved in biological processes. The new term "tyrosyl" was then introduced to designate these residues, and many other biological systems involving such radicals have been described. 4,5 One of the more important recent advances in tyrosyl radical history was achieved in the 1990s with the characterization of the galactose oxidase (GO) active site. 6 -8 For the first time it was demonstrated that tyrosyls could exist coordinated to a metal ion. To better understand this association, chemists have subsequently developed many complexes involving coordinated phenoxyl radicals. 9 -13 Elucidation of the properties of coordination compounds involving redox active ligands, especially those involving sterically hindered phenolates, is one of the most recent and fascinating topics of interest in bioinorganic chemistry. The challenge in this kind of chemistry is the right description of the electronic structure of the M n+ -OPh entity (where OPh represents a phenolate group) once it has been oxidized by one electron. In principle, either the M (n+1)+ -OPh, that is the oxidation is metal based, or the M n+ -• OPh form, that is the oxidation is ligand based, could be obtained. The right description is thus not obvious and, as will be shown below, it strongly depends on the nature of the metal ion, the denticity of the ligand, the substituents of the phenolate precursor and even the temperature. Coordination is also found to improve the radical stability, and exerts an extraordinary control on their magnetic properties and reactivity (regio-and stereoselective oxidations are promoted by a radical). Stable Radicals: Fundamentals and Applied Aspects of Odd-Electron CompoundsEdited by Robin G. Hicks

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Tuning the Electronic Structure of Halidobis(o-imino-benzosemiquinonato)iron(III) Complexes

Cited by 110 publications

References 15 publications

Cobalt(II)/(III) Complexes Containingo-Iminothiobenzosemiquinonato(1−) ando-Iminobenzosemiquinonato(1−) π-Radical Ligands

Cobalt(II)/(III) Complexes Containingo-Iminothiobenzosemiquinonato(1−) ando-Iminobenzosemiquinonato(1−) π-Radical Ligands

Dioxygen binding and activation by a highly reactive Cr(II) compound containing S,N-donors derived from o-aminothiophenol

Metal Coordinated Phenoxyl Radicals

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