Photoinduced charge shift and charge recombination through an alkynyl spacer for an expanded acridinium-based dyadElectronic Supplementary Information (ESI) available: Mass spectrum and cyclic voltammogram for ACR+, delocalisation picture, molecular orbital picture for 1b and crystal structure for derivative where R = SOMe. See DOI: 10.1039/c2cp23273a

The photophysical and electrochemical properties of a dyad comprising an expanded acridinium light-harvester, coupled via a triple bond to a trialkyloxybenzene donor, are described. Laser excitation of the dyad in 1,2-dichloroethane (DCE) results in rapid charge shift (5 ps) followed by slower charge recombination (81 ps) to completely restore the ground state. Discrimination between forward and return electron transfer ( k ret / k for 16) is rather poor. There is no indication of triplet formation on the expanded acridinium-based group following charge recombination. Laser excitation of the dyad results in rapid charge shift and is followed by slower charge recombination to restore the ground state.