Photoinduced reactions between naphthoquinone and N,N,N′,N′-tetramethyl-p-phenylenediamine in the mixture of ionic liquid [BPy][NTf2] and acetonitrile studied by transient spectroscopy

Abstract

Effects of the pyridinium ionic liquid N-butylpyridinium bis((trifluoromethyl)sulfonyl)imide ([BPy][NTf2]) on the photolysis behaviors of 1,4-naphthoquinone (NQ) in the acetonitrile solutions have been investigated by using nanosecond transient absorption techniques. When [BPy][NTf2] existed in the solution, the triplet 3NQ⁎ decayed more slowly and its half lifetime became longer. The photoinduced electron transfer rate constants of NQ and N,N,N′,N′-tetramethyl-p-phenylenediamine (TMPD) in the presence of [BPy][NTf2] were lower than those measured in acetonitrile, but of the same order of magnitude as estimated diffusion controlled rate constant. This finding suggests that [BPy][NTf2] could act as an appropriate solvent for electron transfer reactions. The photoinduced electron transfer reaction rate was determined not only by the viscosity but also by the microstructure of the solvent.