Correlation of zero-field splittings and site distortions. X. Complexes of Mn2+ with mixed ligands

Heming, M.; Remme, S.; Lehmann, Gerhard

doi:10.1016/0022-2364(86)90226-x

Cited by 16 publications

(13 citation statements)

References 37 publications

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“…The Mn( o -phenanthroline) 2 X 2 complexes have smaller D values than the picoline series. The lower values are most likely due to the cis arrangement of their halide ions − vs the trans arrangement of the picoline series, and not the ligand field strength of phenanthroline as was suggested in our earlier report . A range of η values from 0.04 (dichloro) to 0.25 (diiodo) was found for the phenanthroline series; however, high values of η were determined for all three dihalo compounds in an earlier study at low magnetic fields …”

Section: Introductionsupporting

confidence: 47%

An EPR Study of Some Highly Distorted Tetrahedral Manganese(II) Complexes at High Magnetic Fields

et al. 1999

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EPR spectra at 94.5 GHz (3 mm) and 249.9 GHz (1 mm) have been measured for the dichloro-, dibromo-, and diiodobis(triphenylphosphine oxide)manganese(II) complexes. These compounds have a distorted tetrahedral geometry, and the highest possible symmetry obtainable is C 2 v . Because the spectra are taken in the high-field limit, they are simple and much easier to interpret than at lower magnetic fields. Accurate values of the zero-field splitting parameters, D and η (E/D), are determined by least-squares fitting and homotopy using matrix diagonalization. The compounds have g-values near 2 and large values of D and η. Across the series, D increases from 0.165 to 0.906 cm-1, while η decreases slightly from 0.273 to 0.246.

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Section: Introductionsupporting

confidence: 47%

An EPR Study of Some Highly Distorted Tetrahedral Manganese(II) Complexes at High Magnetic Fields

et al. 1999

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“…Moreover, the E / D ratio remained largely constant in this temperature region, indicating that the overall symmetry of the ligand field was not temperature dependent. It has long been known that the zero-field interactions of Mn(II) ions in inorganic solids are pressure and temperature dependent due to their sensitivity to the metal−ligand distances. − For this reason, the simplest explanation for the changes that were observed at low temperatures (<200 K) was the thermal expansion of the protein. If this expansion is linear in temperature, then the changes in Figure correspond to a −2.5 power dependence of D on the Mn(II)−ligand distances.…”

Section: Discussionmentioning

confidence: 99%

Temperature-Dependent Coordination in E. coli Manganese Superoxide Dismutase

et al. 2005

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Two different temperature dependences of the manganese(II) high-field electron paramagnetic resonance spectrum of manganese superoxide dismutase from E. coli were observed. In the 25-200 K range, the zero-field interaction steadily decreased with increasing temperature. This was likely due to the thermal expansion of the protein. From these results, it was possible to deduce an approximately r(-)(2.5) dependence of Mn(II) zero-field interaction on ligand-metal distance. At temperatures above 240 K, a distinct six-line component was detected, the amplitude of which decreased with increasing temperature. On the basis of similarities to the six-line spectrum observed for the azide-complexed E. coli manganese superoxide dismutase, the newly detected six-line spectrum was assigned to a hexacoordinate Mn(II) center resulting from the coordination of a nearby water molecule to the normally five-coordinate center. The changes in enthalpy and entropy characterizing the hexacoordinate-pentacoordinate equilibrium in the 240-268 K range were -5 kcal/mol and -24 cal/mol.K, respectively. The structural implications of the zero-field parameters of the newly found hexacoordinate form in comparison to those of the Mn(II) centers in concanavalin-A and manganese-containing R. spheroides photosynthetic reaction centers and the values predicted by the superposition model are discussed.

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“…Also for the Mn(II) center of superoxide dismutase a simple Gaussian distribution was not sufficient . We interpret the distribution in D and E in terms of a structural variation, i.e., a slight variation of the bond distances and/or bond angles around the manganese, because it is known that subtle structural differences cause significant and detectable changes of the ZFS parameters . These structural differences are visible only in EPR; X-ray studies showed no structural polymorphism .…”

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confidence: 82%

“…29 We interpret the distribution in D and E in terms of a structural variation, i.e., a slight variation of the bond distances and/or bond angles around the manganese, because it is known that subtle structural differences cause significant and detectable changes of the ZFS parameters. 30 These structural differences are visible only in EPR; X-ray studies showed no structural polymorphism. 17 The obtained distribution is broad with D-values between −12 and −8 GHz and a subensemble with a narrow distribution around −9.7 GHz.…”

mentioning

confidence: 98%

A Mononuclear Mn(II) Pseudoclathrochelate Complex Studied by Multi-Frequency Electron-Paramagnetic-Resonance Spectroscopy

Azarkh

Penkova

Kats

et al. 2014

J. Phys. Chem. Lett.

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Knowledge of the correlation between structural and spectroscopic properties of transition-metal complexes is essential to deepen the understanding of their role in catalysis, molecular magnetism, and biological inorganic chemistry. It provides topological and, sometimes, functional insight with respect to the active site properties of metalloproteins. The electronic structure of a high-spin mononuclear Mn(II) pseudoclathrochelate complex has been investigated by electron-paramagnetic-resonance (EPR) spectroscopy at 9.5 and 275.7 GHz. A substantial, virtually axial zero-field splitting with D = -9.7 GHz (-0.32 cm(-1)) is found, which is the largest one reported to date for a Mn(II) complex with six nitrogen atoms in the first coordination sphere.

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Correlation of zero-field splittings and site distortions. X. Complexes of Mn2+ with mixed ligands

Cited by 16 publications

References 37 publications

An EPR Study of Some Highly Distorted Tetrahedral Manganese(II) Complexes at High Magnetic Fields

An EPR Study of Some Highly Distorted Tetrahedral Manganese(II) Complexes at High Magnetic Fields

Temperature-Dependent Coordination in E. coli Manganese Superoxide Dismutase

A Mononuclear Mn(II) Pseudoclathrochelate Complex Studied by Multi-Frequency Electron-Paramagnetic-Resonance Spectroscopy

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