Photo-Induced Electron Transfer from Excited Tris[2,2′-bipyridine-κN1,κN1′]ruthenium(2+) Ions to Dyadic Electron Acceptors That Can Be Protected by Host-Guest Interaction against Fast Back Electron Transfer, Characterization of the Guest Molecules

Abstract

Anthraquinone and viologen moieties were combined to dyadic molecules with two redox centers. These dyades and their constituents were used as acceptors in photo-induced electron-transfer reactions. The experiments show that a caveat is necessary if one tries to derive the properties and the reactions of the dyades from those of their constituents: the spectral properties appear to be independent superpositions of those of the constituents. However, the redox potentials of the two redox centres in the dyades deviate from that of their constituents, the methylene bridge can not suppress a considerable interaction between the two redox centres. This is especially true when the redox potentials of the constituents are close to one another. From the quenching experiments, it can be concluded that electrolyte cations like Na+ are engaged in the transition states of the electron-transfer reactions. In this way, they can control the fate of the transferred electron.