Single-crystal EPR studies of the Fe−O−Fe dimer, [enH2][{Fe(HEDTA)}2O]·6H2O, have been performed at
both X- and Q-band frequencies and room temperature. Resonances arising from the S‘ = 1, 2, and 3 states have
been observed in the powder spectrum at Q-band frequency and analysis by spectral simulation has led to the
zero-field splitting parameters: |D
1| = 1.950 cm-1, |E
1| = 0.650 cm-1, |D
2| = 0.150 cm-1, |E
2| = 0.0195 cm-1,
|D
3| = 0.570 cm-1, and |E
3| = 0.000 cm-1. In addition, analysis of three orthogonal planes of single-crystal EPR
data at both X- and Q-band frequencies has allowed the orientation of the zero-field splitting tensor with respect
to the molecular geometry in the dominant (S‘ = 2) state to be determined. The largest principal value of the D
tensor (D
zz
) is found to lie approximately perpendicular to the plane of the Fe−O−Fe bridge; the nonlinear bridging
angle is 165°. The results obtained in this study are compared with those from a number of other studies. A
pattern for the orientations of the zero-field splitting parameters in the dominant spin state (S‘ = 2) of the Fe−O−Fe dimers, so far studied by single-crystal EPR spectroscopy, emerges.
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Interaction of 1,2,3,4-Tetrahydro-4a-methyl-4aH-carbazole with Dimethyl Acetyl ened ica r boxy late: a Re-exam i nat i on. Crysta I Structures of D i met hyl 2a,3
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