Direct observation of vibrational dynamics in tin phthalocyanine

Charge-transfer (CT)-excited state in phthalocyanine (Pc) tin dichloride is observed by real-time vibrational spectroscopy with a 6-fs pulse laser. Transient negative and positive absorbance change were observed for the CT- and Q-bands, respectively. The observed signal for the CT excitation dominantly couples with intermolecular vibrational modes in the Pc columns, while that for the Q-band couples only the in-plane deformation modes of the Pc macro-cycle. The Q-band, which is the main absorption in the visible and near-infrared region, has no obvious CT character in the primary stage of the photocarrier generation, which suggests the two-step carrier-generation model for Q-band excitation.