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. (C) 2006 Elsevier B.V. All rights reserved.