We optimized the structures of these radicals as free molecules and calculated their magnetic properties at the PBE0/def2-TZVP level with the Gaussian 16 package (see computational details for more information, for validation see ref. [32]). We find that all of them have OSS ground states, and thus AFM interactions between the monomers (Table and Figure ). As expected, all directly connected dimers are twisted along the connecting single bond as free molecules due to the steric hindrance of hydrogen atoms (Figure ). The spin densities in the dimers are mostly localized on the monomer building units, where they maintain the local symmetry as in the monomers (Figures ). To evaluate the strength of magnetic interactions, we calculate the magnetic coupling as defined from the Heisenberg-Dirac-van Vleck (HDVV) Hamiltonian , where and are the spin angular momentum operators on sites 1 and 2, respectively. is calculated by the normalized energy difference between the lowspin and high-spin states, where J > 0 implies FM and J < 0 AFM interaction (see computational details in Supporting Information).