Fig. 3. Free-energy profiles (kcal mol⁻¹) for both the wet (a), and dry (b) mechanisms of Cpd I formation for three different spin states: doublet (black line), quartet (blue line) and sextet (red line). Free energies are estimated with UB3LYP-GD3BJ/6-311+G(2d,2p) with ε = 4 (see text for details).