Ionic liquids containing half-sandwich ruthenium complexes: in situ interconversions via photochemical and thermal ligand exchange

Cyclopentadienyl (Cp) Ru complexes exhibit diverse chemical reactivity and are versatile as catalysts, but their applications to functional materials are yet to be explored. To develop stimuli-responsive liquids based on their reactivity, Ru-containing ionic liquids (ILs) [Ru(Cp)(LL)-L-1]Tf2N (L-1 = N-hexyl-2-pyridinemethanimine; L = CO, MeCN, SMe2, and DMSO) were synthesized in this study. Their colors, physical properties, and chemical reactivities were dependent on the auxiliary ligand L, and these ILs exhibited interconversions via in situ ligand exchange. The exchange from CO to other ligands occurred via UV photoirradiation, whereas the other ligand exchange reactions occurred thermally. On the other hand, [Ru(Cp)L-2(CO)]Tf2N (L-2 = N-methyl-N-hexyl-2-pyridinemethanamine) did not undergo photochemical ligand exchange.