The tamper effect: environmental influence on electron tunneling.

The time constants for electron transfer from the singlet excited state of the small cavity conformer of the tetrabridged coplanar zinc porphyrin quinone (ZnPQ) average 2.4 times as fast in solvents containing XCCl3 group as in solvents of similar dielectric properties. Solvent molecules containing this bulky group cannot fit in the small cavity of conformer ZnPQa. We assign the effect to the increase of the electron wave function in the porphyrin-quinone space by increased exclusion from the electron dense solvent as compared to more usual solvents. We name this property the tamper effect.