Paramagnetic Resonance of Trivalent Manganese in Rutile (Ti<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">O</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>)

Gerritsen, H. J.; Sabisky, E. S.

doi:10.1103/physrev.132.1507

Cited by 163 publications

(152 citation statements)

References 14 publications

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“…A weak intermolecular antiferromagnetic coupling between high-spin Mn III ions can also contribute to the drop of χ M T below 30 K. Mn III complexes usually present an elongated octahedral geometry which corresponds to a negative D parameter. [35] The g and D values deduced here are in agreement with those determined by high-frequency EPR spectroscopy on other Mn III complexes. [36Ϫ39] EPR Spectroscopy X-band EPR spectra of a powder sample of 1(BPh 4 ) 2 ·2CH 3 COCH 3 were recorded at several temperatures between 4.2 and 50 K using the perpendicular detection mode.…”

Section: Magnetic Susceptibility Measurementssupporting

confidence: 78%

Synthesis, Structure and Characterisation of New Phenolato-Bridged Manganese Complexes [L2Mn2]2+ − Formation by Ligand Oxidation in LaH [LaH = N-(2-hydroxybenzyl)-N,N′-bis(2-pyridylmethyl)ethane-1,2-diamine]

Hureau

Anxolabéhère‐Mallart

Nierlich

et al. 2002

Eur. J. Inorg. Chem.

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A mononuclear [L a Mn III OAc](ClO 4 )·0.5H 2 O [2(ClO 4 )·0.5H 2 O] complex with a new amino-containing pentadentate ligand L a H with a [N 4 O] coordination sphere has been obtained. Magnetic susceptibility measurements of 2(ClO 4 )·0.5H 2 O indicated a high spin electronic configuration for the Mn III ion.In cyclic voltammetry the reversible wave observed at E 1/2 = 0.15 V vs. SCE was attributed to the reduction of Mn III into Mn II . In acetonitrile solution complex 2 spontaneously evolved into phenolato-bridged Mn II Mn II dimeric complexes with the concomitant oxidation of the ligand. X-ray diffraction structures revealed that there is indeed a 1:1 mixture of two closely related complexes: in one case both ligands L a − have been oxidised to the imine form leading to the [L i Mn II Mn II L i ] 2+ cation (1a), whereas in the other, only one ligand has been oxidised, leading to the [L a Mn II Mn II L i ] 2+ cation (1b). In both 1a and 1b, Mn II ions are in a distorted octahedral environment. Crystallographic data indicated that the Mn 2 O 2 core is similar for 1a and 1b. The complete spectroscopic and electrochemical studies performed on powder

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Section: Magnetic Susceptibility Measurementssupporting

confidence: 78%

Synthesis, Structure and Characterisation of New Phenolato-Bridged Manganese Complexes [L2Mn2]2+ − Formation by Ligand Oxidation in LaH [LaH = N-(2-hydroxybenzyl)-N,N′-bis(2-pyridylmethyl)ethane-1,2-diamine]

Hureau

Anxolabéhère‐Mallart

Nierlich

et al. 2002

Eur. J. Inorg. Chem.

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“…[12] Hence the term in parentheses becomes negative and we conclude that both hyperfine coupling constants are negative because the parameter P for 55 Mn is positive. Using Equations (9) and (10) together with the experimentally determined A values and the deviation of the g values from the free-electron g value, we obtain P = 0.0170 cm À1 and k = 0.43.…”

Section: Methodsmentioning

confidence: 94%

“…Information concerning the spatial property of the hyperfine interaction matrix requires the use of higher frequencies, as shown in a study of manganese(iii)-doped rutile. [12] In this communication we report single-crystal and powder EPR spectra of the [Mn(H 2 O) 6 ] 3+ ion at high fields and multiple frequencies. To minimize line broadening due to spin-spin dipolar interactions, the [Mn(H 2 O) 6 ] 3+ ion was doped into the diamagnetic cesium gallium alum, Cs-[Ga(H 2 O) 6 ](SO 4 ) 2 ·6 H 2 O, thus enabling the precise determination of the metal hyperfine interaction parameters.…”

mentioning

confidence: 97%

“…The manganese(iii) ion is ubiquitous among chemical systems that exhibit intriguing biological and physical properties, ranging from photosystem II and superoxide dismutase to the celebrated single-molecule magnet Mn 12 . It is for this reason that complexes and clusters of the manganese(iii) ion are widely recognized as the delicicae of high-field electron paramagnetic resonance (EPR) spectroscopists, [1] the fact that they invariably yield good-quality spectra being but a secondary consideration.…”

mentioning

confidence: 99%

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Anisotropic Hyperfine Interaction in the Manganese(III) Hexaaqua Ion

et al. 2005

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The manganese(iii) ion is ubiquitous among chemical systems that exhibit intriguing biological and physical properties, ranging from photosystem II and superoxide dismutase to the celebrated single-molecule magnet Mn 12 . It is for this reason that complexes and clusters of the manganese(iii) ion are widely recognized as the delicicae of high-field electron paramagnetic resonance (EPR) spectroscopists, [1] the fact that they invariably yield good-quality spectra being but a secondary consideration. [2][3][4][5][6][7] Hitherto, the spatial property of the hyperfine interaction between the S = 2 electronic spin and the I = 5/2 nuclear spin in any chemically relevant manganese(iii) compound has escaped observation. There are two fundamental reasons why knowledge of the hyperfine interaction energies is important. First, the magnitude and sign of the anisotropy relate directly to the manganese(iii) coordination sphere. Secondly, the hyperfine interaction has been demonstrated to be instrumental in quantum tunneling of the magnetization in singlemolecule magnets. [8,9] In an EPR study of manganese(iii) superoxide dismutase, [2] the hyperfine splittings were resolved and compared to those documented for a photo-oxidation product of manganese(iii) in the high-affinity site of photosystem II. Consistency was found between the observed hyperfine splitting and the sign of the zero-field-splitting parameter in the two systems. However, these experiments were confined to X-band parallel-mode experiments, which can determine just one component of the hyperfine interaction matrix. Information concerning the spatial property of the hyperfine interaction matrix requires the use of higher frequencies, as shown in a study of manganese(iii)-doped rutile. [12] In this communication we report single-crystal and powder EPR spectra of the [Mn(H 2 O) 6 ] 3+ ion at high fields and multiple frequencies. To minimize line broadening due to spin-spin dipolar interactions, the [Mn(H 2 O) 6 ] 3+ ion was doped into the diamagnetic cesium gallium alum, Cs-[Ga(H 2 O) 6 ](SO 4 ) 2 ·6 H 2 O, thus enabling the precise determination of the metal hyperfine interaction parameters.Pale orange-red crystals of this sample were grown at 0 8C from a saturated 6 m sulfuric acid solution of the cesium gallium alum that contained 1 % cesium manganese alum. A trace of the corresponding chromium(iii) alum was also added. The EPR lines of [Cr(OH 2 ) 6 ] 3+ were readily identified and were useful for crystal alignment.The single-crystal EPR spectra exhibited several magnetically nonequivalent species, reflecting the space group of the host and the propensity of the [Mn(OH 2 ) 6 ] 3+ ion to distort along a Jahn-Teller active coordinate. There are four tervalent cations in the cubic unit cell, each occupying a site of S 6 symmetry on one of the four unique threefold axes of the unit cell. In addition, at low temperatures the [Mn(OH 2 ) 6 ] 3+ ion is expected to be locked into one of the three possible tetragonally elongated structures that results from the JahnTelle...

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“…The theoretical prediction of κ is a rather difficult task; however, quite interestingly, κ is observed experimentally to be nearly constant for a given oxidation state of the ion and at different ligand configurations (57,60). The experimental value κ ) 0.52 was determined for Mn 3+ in TiO 2 (56). We accept this value for the purpose of our analysis and assume κ ) 0.5 being a constant and thus focus on changes to PR 2 as the most significant source of the change in A Z .…”

Section: Illumination At -20°c Produces a Maximal Yield Of Mnmentioning

confidence: 99%

Spectroscopic Evidence for Ca²⁺Involvement in the Assembly of the Mn₄Ca Cluster in the Photosynthetic Water-Oxidizing Complex

et al. 2006

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Biogenesis and repair of the inorganic core (Mn 4 CaO x Cl y ), in the water-oxidizing complex of photosystem II (WOC-PSII), occurs through the light-induced (re)assembly of its free elementary ions and the apo-WOC-PSII protein, a reaction known as photoactivation. Herein, we use electron paramagnetic resonance (EPR) spectroscopy to characterize changes in the ligand coordination environment of the first photoactivation intermediate, the photo-oxidized Mn 3+ bound to apo-WOC-PSII. On the basis of the observed changes in electron Zeeman (g eff ), 55 Mn hyperfine (A Z ) interaction, and the EPR transition probabilities, the photogenerated Mn 3+ is shown to exist in two pH-dependent forms, differing in terms of strength and symmetry of their ligand fields. The transition from an EPR-invisible low-pH form to an EPR-active high-pH form occurs by deprotonation of an ionizable ligand bound to Mn 3+ , implicated to be a water molecule: [Mn 3+ (OH 2 In the absence of Ca 2+ , the EPR-active Mn 3+ exhibits a strong pH dependence (pH ∼6.5-9) of its ligand-field symmetry (rhombicity ∆δ ) 10%, derived from g eff ) and A Z (∆A Z ) 22%), attributable to a protein conformational change. Binding of Ca 2+ to its effector site eliminates this pH dependence and locks both g eff and A Z at values observed in the absence of Ca 2+ at alkaline pH. Thus, Ca 2+ directly controls the coordination environment and binds close to the highaffinity Mn 3+ , probably sharing a bridging ligand. This Ca 2+ effect and the pH-induced changes are consistent with the ionization of the bridging water molecule, predicting that [ A single tight-binding Ca 2+ ion is essential for photosynthethic O 2 evolution activity in ViVo (1-5). Calcium is located within the water-oxidizing complex of photosystem II (PSII-WOC), 1 comprised of an oxo/aquo-bridged inorganic core whose stoichiometry, Mn 4 CaO x , is based on several lines of evidence, including X-ray absorption (6-9), electron paramagnetic resonance (EPR) spectroscopy (10,11), and the recent X-ray diffraction (XRD) data (12, 13). Mn-, Sr-, and Ca-extended X-ray absorption fine structure (EXAFS) spectroscopies accurately place the calcium effector site at 3.3-3.5 Å from Mn atoms. However, the relative position of Ca 2+ within the Mn 4 O x cluster differs according to which type of data is emphasized and the assumptions of the models used to interpret the raw data. Spectroscopic and XRD data have constrained the possible core topologies to only a few types, with the structures given in Chart 1 proposed on the basis of one or more lines of evidence (9)(10)(11)13). These structural proposals have led to a number of mechanistic proposals for the role of calcium in O 2 evolution reviewed elsewhere (11,(14)(15)(16)(17).Dissection of the functional roles of the inorganic cofactors has come from in Vitro studies of the photoactivation process, which is defined as the assembly of the inorganic core during biogenesis and repair of the WOC. In Vitro photoactivation of the WOC is described by the following ...

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Paramagnetic Resonance of Trivalent Manganese in Rutile (TiO2)

Cited by 163 publications

References 14 publications

Synthesis, Structure and Characterisation of New Phenolato-Bridged Manganese Complexes [L2Mn2]2+ − Formation by Ligand Oxidation in LaH [LaH = N-(2-hydroxybenzyl)-N,N′-bis(2-pyridylmethyl)ethane-1,2-diamine]

Synthesis, Structure and Characterisation of New Phenolato-Bridged Manganese Complexes [L2Mn2]2+ − Formation by Ligand Oxidation in LaH [LaH = N-(2-hydroxybenzyl)-N,N′-bis(2-pyridylmethyl)ethane-1,2-diamine]

Anisotropic Hyperfine Interaction in the Manganese(III) Hexaaqua Ion

Spectroscopic Evidence for Ca²⁺Involvement in the Assembly of the Mn₄Ca Cluster in the Photosynthetic Water-Oxidizing Complex

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Paramagnetic Resonance of Trivalent Manganese in Rutile (TiO2)

Cited by 163 publications

References 14 publications

Synthesis, Structure and Characterisation of New Phenolato-Bridged Manganese Complexes [L2Mn2]2+ − Formation by Ligand Oxidation in LaH [LaH = N-(2-hydroxybenzyl)-N,N′-bis(2-pyridylmethyl)ethane-1,2-diamine]

Synthesis, Structure and Characterisation of New Phenolato-Bridged Manganese Complexes [L2Mn2]2+ − Formation by Ligand Oxidation in LaH [LaH = N-(2-hydroxybenzyl)-N,N′-bis(2-pyridylmethyl)ethane-1,2-diamine]

Anisotropic Hyperfine Interaction in the Manganese(III) Hexaaqua Ion

Spectroscopic Evidence for Ca2+Involvement in the Assembly of the Mn4Ca Cluster in the Photosynthetic Water-Oxidizing Complex

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Spectroscopic Evidence for Ca²⁺Involvement in the Assembly of the Mn₄Ca Cluster in the Photosynthetic Water-Oxidizing Complex