Polyether-Bridged Sexithiophene as a Complexation-Gated Molecular Wire for Intramolecular Photoinduced Electron Transfer

摘要

Well-defined alpha-oligothiophenes are particularly promising as molecular wires.In the previous study of the porphyrin-oligo-thiophene-fullerene triad 1,we actually found that the oligoth-iophene spacer can undergo efficient photoinduced electron transfer from the porphyrin chromophore to the fullerene.It is essential in molecular electronics that the electron transfer properties of molecules can be controlled by an external stimulus (gate function).Swager and co-workers reported that polythiophene systems modified with crown ethers display ionochromic responses.This has prompted us to examine the possibility that crown ether-integrated oligothiophenes can behave as metal complexation-gated molecular wires.Inclusion of an alkaline-metal cation in the crown ether ring is expected to restrict the conformation of the oligothiophene backbone,resulting in a geometrical change crucial to electron transfer.We now report the photophysical properties of the novel porphyrin-sexithiophene-fullerene triad 2 (abbreviated as Po- 6T-C_(60)),where the two central thiophene units of the sexithiophene spacer are bridged by a crown-ether-like polyether chain,where the reversible control of the photoinduced electron transfer is possible by metal complexation/decomplexation.