Analogously to what was found for 1, it can be expected that the transition frequency of peak 2A corresponds to the expected energy gap between ground and excited KDs. A similar structure to what was observed for 1 is observed here for 2. At the position of the second field-dependent peak (2B) found for 2, nothing can be observed in the FIR spectra recorded on 1, and it is tempting to link the corresponding excitation to the exchange coupling between metal and radical spins. In the variable-field Raman spectra for 2 (Fig. , S8, S9), features are found at similar but slightly lower frequencies, indicating a more complex origin of these peaks than simple magnetic resonance or electronic transitions. In addition, the Raman spectra show two further peaks at higher energies of 917 cm -1 (2C) and 1063 cm -1 (2D), again reminiscent of what was found for compound 1.