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The dinuclear radical anion complexes {(μ-L)[Re(CO)₃Cl]₂}^•-, L = 2,2‘-azobispyridine (abpy) and 2,2‘-azobis(5-chloropyrimidine) (abcp), were investigated by EPR at 9.5, 94, 230, and 285 GHz (abpy complex) and at 9.5 and 285 GHz (abcp complex). Whereas the X-band measurements yielded only the isotropic metal hyperfine coupling of the ^185,187Re isotopes, the high-frequency EPR experiments in glassy frozen CH₂Cl₂/toluene solution revealed the g components. Both the a(^185,187Re) value and the g anisotropy, g₁ − g₃, are larger for the abcp complex, which contains the better π-accepting bridging ligand. Confirmation for this comes also from IR and UV/vis spectroscopy of the new {(μ-abcp)[Re(CO)₃Cl]₂}^o/•-/2- redox system. The g values are reproduced reasonably well by density functional calculations which confirm higher metal participation at the singly occupied MO and therefore larger contributions …