2. Heisenberg-Dirac-Van Vleck Hamiltonian: PATFIA (Magnet 1, Ref. ) and tris-(3-acetylamino-1,2,4-triazolate) motif of HUKDOG (Magnet 2, Ref. ), copper single molecule magnets (SMMs). Geometry of Magnet 1 optimized with ωB97X-D/cc-pVTZ for the triplet state was taken from Ref. . As in Ref. , the ferrocene group was not included in the structure. We also did not consider water molecules, sulfate groups, and perclorate anions in the structure of Magnet 2. The geometry of Magnet 2 was optimized with ωB97X-D/cc-pVTZ and is given in the SI.