Novel photo-induced aggregation behavior of a supramolecular system containing iron(III) magnetic ionic liquid and azobenzene

New photo-controllable supramolecular system containing magnetic ionic liquid (iron(III) chloride with 1-butyl-3-methylimidazolium chloride) and azobenzene has been prepared. Reversible structural changes due to cis–trans photoisomerization of azobenzene could be observed by means of resonance Raman and electronic spectroscopy. Field dependence of magnetic moment at 298 K exhibited paramagnetic behavior similar to pure iron(III) magnetic ionic liquid. Alternate irradiation of UV and visible light at 298 K resulted in a monotonous increase of magnetic moment. In analogy with previous study, the novel behavior can be explained as irreversible aggregation of paramagnetic iron(III) complexes forming a short-range order in the supramolecular system.