Generation of long-lived methylviologen radical cation in the triplet-state mediated electron transfer in a β-cyclodextrin based supramolecular triad

A novel tris(bipyridyl)ruthenium-pyrene-methylviologen supramolecular triad was assembled through inclusion complexation of adamantane-linked Ru(II)-Py dyad in MV2+-linked β-cyclodextrin. Excitation of the Ru(II) chromophore populated its 3MLCT which upon energy transfer gave 3Py, which donates an electron to MV2+ to give Ru(II)-Py•+-MV•+. A second electron transfer then occurs from Ru(II) to Py•+ to give the supramolecular Ru(III)-Py-MV•+ charge separated state. Laser flash photolysis experiments confirmed formation of MV•+ which exhibited 100 μs lifetime. Steady state irradiation of the self-assembled system in the presence of sacrificial donor also led to formation of long-lived MV•+. © 2014 Elsevier B.V. All rights reserved.