Figure 3.

Classical model for photosubstitution reactions in ruthenium(II) polypyridyl complexes. (a) Molecular energy of the different states involved in the photochemistry of ruthenium(II) polypyridyl complexes. Gray pathways generate ¹O₂ in the presence of dioxygen; black pathways remain in the absence of O₂. k_ISC, k_nr, k′_nr, k_P, and k_TTET are rate constants for intersystem crossing, non-radiative decay, phosphorescence, and triplet–triplet energy transfer, respectively. ΔG^⧧_a is the activation barrier for the conversion of the ³MLCT to the ³MC state, and ΔG₀ = G(³MC) – G(³MCLT). ³SA represents a Solvent Adduct of the complex in the triplet state. (b) Orbital energy scheme of the excited states involved in photosubstitution. Numerical values for bond lengths are indicated for [Ru(tpy)(bpy)(Hmte)]²⁺ (Figure 2), as reported in ref (50).