Several of the dissociations in the triplet spin state ended in Cu(I) and triplet O 2 with an average dissociation energy of 55.7 ± 30.6 kJ/mol (n = 6) with B3LYP. However, in a few cases (more for TPSS than for B3LYP), a Cu(II) and O • - 2 state was obtained. Also in these cases the average dissociation energy was significantly uphill with 84.9 ± 6.8 kJ/mol (n = 2) with B3LYP. In most cases, the dissociations in the open-shell singlet state are higher in energy than the triplet.