Effect of N‑butyl‑pyridinium bis(trifluoromethyl sulfonyl)imide on the photoinduced electron transfer between duroquinone and amines

Abstract

The photoinduced electron transfer (PET) reactions have been characterized using laser flash photolysis, wherein a photoexcited acceptor, the excitation triplet state of duroquinone (3DQ⁎), abstracts an electron from a ground state donor, aniline or diphenylamine. After adding the ionic liquid (IL) N‑butyl‑pyridinium bis(trifluoromethyl sulfonyl)imide ([BPy][NTf2]) to acetonitrile (MeCN) solution, the decay of 3DQ⁎ became slower and the efficiency of electron transfer also decreased, while the lifetimes of radicals which generated from PET turned longer. In addition, the reaction rate in the IL/MeCN mixed system was lower than that in MeCN, which is not consistent with the previous report that [BPy][NTf2] facilitated the PET reactions. It could be found that the PET reaction was very weak under oxygen condition, which indicates that oxygen quenching reaction plays a primary role in the mixed IL/MeCN solution. It was also found that the measured rate constants were all lower than the estimated diffusion rate constants in either pure acetonitrile solution or in IL-co-solvent mixture. This finding suggests that the viscosity and the diffusion rate have great impacts on the PET process.