which can be employed to compute spin-contamination corrected quartet-doublet energy gaps using broken-symmetry DFT computations. Within the DFT framework, an alternative tool in the electronic structure toolbox to evaluate the doublet-quartet energy gap is the spinconstraint DFT (CBS-DFT) which provides the advantage of calculating the total energy by constraining the spin-magnetic moment on the specified spatial zones. The doubletquartet energy gap is then calculated employing Eq. 6 using CBS-DFT calculated energies.