Influence of Molecular Oxygen on the Charge Transfer Properties of a Co(II)Porphyrin-Al(III)Phthalocyanine Aggregate. Excited States Dynamics and Photobiological Activities (original) (raw)

1999, The Journal of Physical Chemistry A

We report the novel cooperative properties of a complex obtained by self-assembling in solution a tetracationic cobalt porphyrin, Co II P 4+ , and a tetraanionic sulfoaluminum phthalocyanine, Al III Pc 4-. In the ground state, the complex displays a charge transfer character, Co II-δ P 4+ /(Al III Pc 4-) +δ , and the oxidation of the phthalocyanine moiety is catalyzed in the presence of its partner. In aerated media, the neutral complex strongly binds molecular oxygen to form a stable zwitterionic species,-O 2 Co II P 4+ /(Al III Pc 4-) +˚. The zwitterion can revert to the neutral form Co II-δ P 4+ /(Al III Pc 4-) +δ upon vigourous bubbling of the solution with an inert gas (N 2 , Ar) or under light stimuli. In the excited state, the complex photoejects the oxygen and relaxes to the ground state via a triplet excited state. The latter species can transfer its excess energy to nearby oxygen molecules. The mechanism of photoproduction of 1 O 2 was studied via steady-state and time-resolved absorption and fluorescence techniques over a wide time window, from nanoseconds to hundreds of femtoseconds. We also investigated the potentiality of the neutral and zwitterionic complexes as a sensitizer for the photodynamic inactivation of cancer cells.

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