Charge transfer, LMCT states

Such reactions are commonly found as a result of the decomposition of charge transfer excited states. For example, while excitation of the MC bands of Co(NH3)5X (X = Cl, Br, I) leads to photosolvation and the formation of Co(NH3)5(0112) and Co(NH3)4(OH2)X, shorter wavelengths yield the LMCT state which decomposes into Cc II) ions and halogen atoms. The quantum yield for the reaction is found to depend on the excitation energy, indicating a role for the initially formed radical pair (Eq. 5). This may reform the starting complex (Eq. 6) or decompose to the redox products stabilised by the solvent or some other species (Eq. 7). The Co(II) complexes eventually decomposes (Eq. 8). 

The emission spectrum of compound 8 exhibits in the solid state at room temperature an intense emission at 558 nm after excitation at 371 nm. According to the photoluminescent properties of Cu4I4 clusters, the emission band might be assigned to a combination of iodide-to-copper charge transfer (LMCT) and d-s transitions by Cu—Cu interaction within Cu3 clusters. 

Figure 6.7 Inner-sphere redox processes induced by different CT (charge transfer) excited states in transition metal complexes. LMCT, ligand-to-metal charge transfer MLCT, metal-to-ligand charge transfer...

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