Picosecond photochemistry of a cofacial diporphyrin containing iron(III) and zinc(II): Mimicking electron transfer between cytochrome c and the primary electron donor in reaction centers of photosynthetic bacteria

Comparison of picosecond kinetic and spectroscopic data for Zn octaethylporphine and Fe(III)Cl octaethylporphine with that for Zn—Fe(III)Cl, a cofacial diporphyrin composed of a Zn porphyrin covalently bound to an Fe(III)Cl porphyrin with two chains of five atoms each, supports the assignment of a light-driven electron transfer (k > 10¹¹s^-1) within Zn—Fe(III)Cl to form [Zn⁺·—Fe(II)]Cl. The kinetics (k ≈ 10¹⁰s^-1) and thermodynamics of the reverse electron transfer are compared to those of a similar electron transfer in bacterial photosynthesis, the reduction of an oxidized bacteriochlorophyll dimer, (BChl)₂⁺·, by Fe(II) cytochrome c.