Fig. 3. Mid-infrared transient absorption spectra in the symmetric and anti-symmetric imide carbonyl stretching region measured after excitation at 375 nm of dyads with different driving force for charge separation, −ΔGCS, in acetonitrile (ACN) (A) and methylcyclohexane (MCH) (B). (C) UV-Visible transient absorption spectra measured with IIIa in different solvents. The presence of the band “X” around 23 000 cm−1 follows the same solvent dependence as the S1(π–π*)–Tn(n–π*) equilibrium constant K and is therefore attributed to the triplet charge-separated state.
