An Efficient Indirect Mechanism for the Ultrafast Intersystem Crossing in Copper Porphyrins - Archive ouverte HAL
Article Dans Une Revue Journal of Physical Chemistry A Année : 2013

An Efficient Indirect Mechanism for the Ultrafast Intersystem Crossing in Copper Porphyrins

Résumé

The ultrafast dynamics of copper tetraphenylporphyrin (CuTPP), copper octaethylporphyrin (CuOEP), and of the free base tetraphenylporphyrin (H2TPP), excited in the S2 state have been investigated in the gas phase by femtosecond pump/probe experiments. The porphyrins were excited in the Soret band at 400 nm. Strikingly, the S2-S1 internal conversion in H2TPP is very rapid (110 fs), as compared to that of ZnTPP (600 fs), previously observed. In turn, CuTPP and CuOEP, excited in S2, follow an efficient and different relaxation pathway from that of other open-shell metalloporphyrins. These two molecules exhibit a sequential four-step decay ending on a slow evolution in the nanosecond range 2S2 → 2CT → 2T → 2Ground State. This latter evolution is linked to the formation of the 2T, tripdoublet state in CuTPP, observed in the condensed phase. It is shown that an intermediate charge transfer state plays a crucial role in linking the porphyrin centered 1ππ* and 3ππ* configurations. A simple model is presented that allows a rapid evolution between these two configurations, via coupling of the porphyrin π system with the free d electron on the copper. The mechanism obviates the need for the spin orbit coupling within the porphyrin. The result is that these copper porphyrins can exhibit an ultrafast apparent intersystem crossing, unprecedented for organic molecules.
Fichier non déposé

Dates et versions

hal-00955732 , version 1 (05-03-2014)

Identifiants

Citer

M.-H. Ha-Thi, N. Shafizadeh, L. Poisson, B. Soep. An Efficient Indirect Mechanism for the Ultrafast Intersystem Crossing in Copper Porphyrins. Journal of Physical Chemistry A, 2013, 117 (34), pp.8111-8118. ⟨10.1021/jp4008015⟩. ⟨hal-00955732⟩
43 Consultations
0 Téléchargements

Altmetric

Partager

More