Vibronic Coupling Drives the Ultrafast Internal Conversion in a Functionalized Free-Base Porphyrin

Vasilis Petropoulos, Pavel S. Rukin, Frank Quintela, Mattia Russo, Luca Moretti, Ana Moore, Thomas Moore, Devens Gust, Deborah Prezzi, Gregory D. Scholes, Elisa Molinari, Giulio Cerullo, Filippo Troiani, Carlo A. Rozzi, Margherita Maiuri

Research output: Contribution to journalArticlepeer-review


Internal conversion (IC) is a common radiationless transition in polyatomic molecules. Theory predicts that molecular vibrations assist IC between excited states, and ultrafast experiments can provide insight into their structure-function relationship. Here we elucidate the dynamics of the vibrational modes driving the IC process within the Q band of a functionalized porphyrin molecule. Through a combination of ultrafast multidimensional spectroscopies and theoretical modeling, we observe a 60 fs Qy-Qx IC and demonstrate that it is driven by the interplay among multiple high-frequency modes. Notably, we identify 1510 cm-1 as the leading tuning mode that brings the porphyrin to an optimal geometry for energy surface crossing. By employing coherent wave packet analysis, we highlight a set of short-lived vibrations (1200-1400 cm-1), promoting the IC within ≈60 fs. Furthermore, we identify one coupling mode (1350 cm-1) that is responsible for vibronic mixing within the Q states. Our findings indicate that porphyrin-core functionalization modulates IC effectively, offering new opportunities in photocatalysis and optoelectronics.

Original languageEnglish (US)
Pages (from-to)4461-4467
Number of pages7
JournalJournal of Physical Chemistry Letters
Issue number16
StatePublished - Apr 25 2024

All Science Journal Classification (ASJC) codes

  • General Materials Science
  • Physical and Theoretical Chemistry


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