where D and E describe the axial and rhombic terms of the anisotropy, with |𝐷| ≥ 3𝐸 ≥ 0 (see Table ). All employed approaches predict susceptibility and magnetisation curves that match well with the experimental values (Figure ). We note, however, that the sudden drop in 𝜒𝑇 product could not be explained with this modelthe only other option we could think of involves intermolecular antiferromagnetic interactions, which is not supported by the crystal data. We then proceeded with the characterization of 1-Eu via continuous-wave Electronic Paramagnetic Resonance (cw EPR) spectroscopy. Variable temperature (VT) X-band spectra of 1-Eu recorded between 5 K and 291 K show a similar overall shape, but also display significant variations in the relative intensities across the temperature range (Figure , left), indicating. the presence of multiple thermally accessible states with different magnetic character. The Q-band spectrum, measured at room temperature, presents a much richer structure, which was used to test the validity of our computational approach. Unfortunately, using the CASSCF-SO obtained parameters, the agreement between experiment and simulation is poor (Table , Figure and). However, assuming a model spin Hamiltonian as indicated in Eq. 1, we were able to simulate the Q-band spectrum (Figure , right) while also reproducing the main features of the X-band spectrum at room temperature (Figure , top)