Vinyl spacers—tuning electron transfer through fluorene-based molecular wires

Rigid and soluble electron donor-acceptor conjugates (3 and 11) that combine [small pi]-extended tetrathiafulvalene (exTTF) as an electron donor and C60 as an electron acceptor have been synthesized using oligo-vinylfluorene (oFV) linkers to connect the electroactive entities. Fluorescence and transient absorption measurements confirm that light-induced excitation induces charge-transfer reactions over distances of 28 A in THF. The incorporation of vinylene spacers into oligofluorene molecular wires has been shown both experimentally and theoretically to improve the charge-transfer features significantly to give a [small beta] value of 0.075 +/- 0.001 A-1. Enhanced [small pi]-conjugation caused by higher orbital overlap is responsible for this trend.