In a molecular triad comprised of a central naphthalene diimide (NDI) unit flanked by two [Ru(bpy)] (bpy = 2,2'-bipyridine) sensitizers, NDI is formed after irradiation with visible light in deaerated CHCN in the presence of excess triethylamine. The mechanism for this electron accumulation involves a combination of photoinduced and thermal elementary steps. In a structurally related molecular pentad with two peripheral triarylamine (TAA) electron donors attached covalently to a central [Ru(bpy)]-NDI-[Ru(bpy)] core but no sacrificial reagents present, photoexcitation only leads to NDI (and TAA), whereas NDI is unattainable due to rapid electron transfer events counteracting charge accumulation. For solar energy conversion, this finding means that fully integrated systems with covalently linked photosensitizers and catalysts are not necessarily superior to multicomponent systems, because the fully integrated systems can suffer from rapid undesired electron transfer events that impede multielectron reactions on the catalyst.

A molecular triad comprising a [Ru(bpy) 3 ] 2+ (bpy = 2,2′-bipyridine) photosensitizer, a primary phenothiazine (PTZ) donor and a secondary (extended) tetrathiafulvalene (exTTF) donor was synthesized and explored by UV/Vis transient absorption spectroscopy. Initial photoinduced electron transfer from PTZ to the 3 MLCT-excited [Ru(bpy) 3 ] 2+ occurs within less than 60 ps, and subsequently PTZ is regenerated by electron transfer from exTTF with a time constant of 300 ps. The resulting photoproduct comprising exTTF ·+ and [Ru(bpy) 3 ] + has a lifetime of 6100 ps in de-aerated CH 3 CN at room temperature. Additional one-and two-pulse laser flash photolysis studies of the triad were performed in the presence of excess methyl viologen [a]

No abstract

No abstract

No abstract