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Issue 19, 1991
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Electron paramagnetic resonance studies of radical pairs [M(CO)5]2(M = Cr, Mo, W) trapped in single crystals of PPh+4HM(CO)5

Abstract

γ-Irradiated single crystals of PPh+4HM(CO)5(M = Cr, Mo, W) exhibit powerful EPR spectra due to two distinct interacting pairs of M(CO)5 radicals. g- and fine-structure (D) matrices were determined from measurements at 77 K of EPR spectra obtained as a function of angle in the ac and aa′ planes of crystallographically aligned single crystals of the Mo and W compounds. The data are compared with those obtained previously for the Cr compound. In all three cases, g and one of the D-tensors are aligned with the tetragonal c-axis of the crystal, and the principal g-values are appropriate for d7 square-pyramidal M(CO)5 radicals. Classical dipolar calculations show that the two radical pairs correspond to the closest and next-closest pair of undamaged anions in the crystals, the former lying along c and the latter along a skew direction. The D-values for the Mo and W closest pairs indicate a substantial contribution from anisotropic exchange to the coupling of the two unpaired electrons.

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Article type: Paper
DOI: 10.1039/FT9918703121
Citation: J. Chem. Soc., Faraday Trans., 1991,87, 3121-3127
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    Electron paramagnetic resonance studies of radical pairs [M(CO)5]2(M = Cr, Mo, W) trapped in single crystals of PPh+4HM(CO)5

    R. C. Hynes, K. F. Preston, J. J. Springs, J. S. Tse and A. J. Williams, J. Chem. Soc., Faraday Trans., 1991, 87, 3121
    DOI: 10.1039/FT9918703121

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