Picosecond time-resolved resonance Raman spectroscopy of the charge separated state of Mg-free base diporphyrins

The photoinduced charge separated state of a covalently linked magnesium porphyrin and free base porphyrin heterodimer complex (MgH2) was investigated by picosecond time-resolved, two-color, pump-probe resonance Raman spectroscopy. The charge separated state is detected within 30 ps of laser excitation; recombination occurs within 500 ps. In the charge separated state of the MgH2 diporphyrin complex, vibrational mode correlations showed that the magnesium porphyrin cation half of the dimer is in its 2A1u electronic state and the free base porphyrin anion half of the charge transfer state has vibrational characteristics that are interpreted in terms of data available on the free base octaethylporphyrin anion.