Substituent effects on the photoreactivity of Ru-containing ionic liquids exhibiting reversible ionic conductivity changes

Abstract

Controlling the ionic conductivity of liquids using external fields is crucial for electronic device applications. We have recently developed metal-containing ionic liquids (ILs) exhibiting reversible ionic conductivity changes upon UV photoirradiation and heating based on the photochemical oligomerization reaction of sandwich Ru complexes. In this study, to explore the controllability of the reaction, we synthesized several Ru-containing ILs with different substituents containing a cyano or dimethylamino group at the terminal position. The photochemical reaction was significantly affected by the coordination ability and flexibility of the substituents, and mixing ILs having different reactivity allowed controlling the conversions. Upon successive photoirradiation–heating cycles, the ionic conductivity of these ILs underwent reversible changes, whose extent reflected the photoreactivity of the ILs.