Ultrafast photochemistry of free-base porphyrin: a theoretical investigation of B -\textgreater Q internal conversion mediated by dark states - Aix-Marseille Université Accéder directement au contenu
Article Dans Une Revue Physical Chemistry Chemical Physics Année : 2018

Ultrafast photochemistry of free-base porphyrin: a theoretical investigation of B -\textgreater Q internal conversion mediated by dark states

Résumé

We examine the mechanism of ultrafast internal conversion between the B band (Soret band) and the Q band in porphine (H2P), the prototypical free-base porphyrin, using electronic structure studies and on-the-fly surface-hopping nonadiabatic dynamics. Our study highlights the crucial role of dark states within the N band which are found to mediate B/Q state transfer, necessitating a treatment beyond Gouterman's classic four-orbital model. The sequential B -\textgreater N -\textgreater Q pathway dominates largely over the direct B -\textgreater Q pathway which is found to be energetically unfavorable. Potential energy surface cuts and conical intersections between excited states are determined by TDDFT and validated by CASSCF/CASPT2 and XMCQDPT2 calculations. Both the static analysis and on-the-fly surface-hopping calculations suggest a pathway which involves minor structural deformations via in-plane vibrations. The B -\textgreater N conversion is a bar rierless adiabatic process occurring within similar to 20 fs, while the subsequent N -\textgreater Q conversion occurs via a conical intersection within similar to 100 fs, in agreement with time-resolved experiments for porphine and related free base porphyrins. Furthermore, evidence for both sequential and direct transfer to the Q(x) and Q(y) states is obtained.

Domaines

Chimie

Dates et versions

hal-02091908 , version 1 (06-04-2019)

Identifiants

Citer

Konstantin Falahati, Carsten Hamerla, Miquel Huix-Rotllant, Irene Burghardt. Ultrafast photochemistry of free-base porphyrin: a theoretical investigation of B -\textgreater Q internal conversion mediated by dark states. Physical Chemistry Chemical Physics, 2018, 20 (18), pp.12483--12492. ⟨10.1039/c8cp00657a⟩. ⟨hal-02091908⟩
124 Consultations
0 Téléchargements

Altmetric

Partager

Gmail Facebook X LinkedIn More