Tuning the Charge-Separated Lifetimes of Ruthenium(II)polypyridyl-Viologen Dyads and Ruthenium(II)polypyridyl-Viologen Triads by the Formation of Supramolecular Assemblies with Crown Ethers

Abstract

The synthesis and photophysical properties of a ruthenium dyad (4) and triad (5) are reported. Both biomimetic systems are physical models for the photosynthetic reaction center. They consist of a ruthenium(II)-polypyridyl sensitizer featuring chemically attached 3,3‘-dimethyl-4,4‘-viologen and 4,4‘-viologen electron acceptors. The binding of the chemically attached electron acceptors by the three structurally different crown ethers, DB30C10, BBO5O5, and AAO5O5, offers a remarkable tool for the enhancement of the lifetimes of the charge separated states (τCS), up to a factor of 2 × 104. The drastic increase in the lifetimes observed can be explained by a decrease in the reorganization energy λ due to the presence of the crown ether units bound to the viologen acceptor.