Observations of the whole bell-shaped energy gap law in the intra-molecular charge separation (CS) from S2 state of directly linked Zn–porphyrin–imide dyads: Examinations of wider range of energy gap (−ΔGCS) for the CS rates in normal regions

Very recently, we have succeeded in the first observation of the whole bell-shaped energy gap law (EGL) of photoinduced charge separation (CS) reaction, examining the ultrafast reaction from the S2 state of Zn–porphyrin–imide dyads with the fs fluorescence dynamics measurements, which showed EGL including both normal and inverted regimes considerably broader than the result in our previous investigations. We have concluded that the very broad EGL is due to the coupling of intrachromophore high frequency vibrational modes with CS from S2, which results in the single exponential fluorescence decay in 100 fs regime in various solvents of different polarities and viscosities.