Fe3+ doped polyaniline (PANI) films containing azobenzene derivatives in the side chain have been prepared. Photoisomerization of the azobenzene derivative in the PANI films was observed at room temperature. Furthermore, Fe-57 Mossbauer measurements showed that the ligand-metal bond distance and the symmetry around the Fe3+ were influenced by the photoisomerization. (C) 2007 Elsevier B.V. All rights reserved.