Fig. 4. (a) B3LYP UV-vis absorption spectrum of Pt-Fe simulated in both DMSO (blue solid) and water (red dashed). The regions of interest are labelled as (I), (II) and (III); (b) NTO plots for S11 and S25 singlet states and relative theoretical assignments for hole-to-particle transitions. MMCT: Fe(ii) to Pt(IV), and LMCT: ligand-to-Pt (IV), contributions are shown on Fig. 4c, and listed in Table S9†); (c) energy diagram of the low-lying excited singlet (blue) and triplet (orange) states of Pt-Fe computed with respect to the ground-state zero energy. Solid lines identify the most important singlets and triplet states. Only the most probable couplings (ISC) of each singlet state with the triplet states lying below are highlighted (green dashed lines).