For complexes 2-Ln and [4-Ln] 0 , the active space consisted of the seven f orbitals. An unrestricted KS-DFT calculation on the sextet states was performed to obtain initial orbitals for [4-Sm] 0 . For the cations of 4-Ln, the active space consisted of the seven f orbitals and one N-O π* orbital of TEMPO (Figure ). The optimized orbitals of Extended multistate complete active space second order perturbation theory (XMS-CASPT2) calculations with an IPEA shift of 0.25 were performed in CASPT2 for 2-Yb, [4-Yb] 0 and attempted for 4-Yb (did not converge). Selected CASSCF spin-free roots (Table ) or the mixed spin-free wavefunctions from XMS-CASPT2 were mixed by spin-orbital coupling in RASSI. The magnetic susceptibility and magnetization vs field was calculated in SINGLE_ANISO. For calculations on 2-Ln and [4-Ln] 0 the spin-orbit wavefunctions were decomposed into a CF Hamiltonian with the z-direction defined by the g1 vector of the ground state doublet or pseudo-doublet.