Electron transfer in porphyrin complexes in different solvents

Electron transfer (ET) in different solvents is investigated for systems co nsisting of donor, bridge, and acceptor. It is assumed that vibrational rt laxation is much faster than the ET. ET rates and final populations of the acceptor state are calculated numerically and in an approximate fashion ana lytically. In wide parameter regimes these solutions are in very good agree ment. The theory is applied to the ET in H2P-ZnP-Q, with free-base porphyri n (H2P) being the donor, zinc porphyrin (ZnP) the bridge, and quinone (Q) t he acceptor. It is shown that the ET rates can be controlled efficiently by changing the energy of the bridging level, which can be done by changing t he solvent. The solvent effect is determined for different models.