The synthesis of a conjugated polymer containing pyridyl units in the polymer backbone was successfully carried out with 2,6-dibromopyridine and a diboronic acid derivative via the Suzuki coupling reaction. This polymer had a number average molecular weight of 4000 and excellent solubility in conventional organic solvents; this suggested the effect of the incorporation of dialkoxy side chains. A metallochromic phenomenon with ferric ions was clearly observed in spin-coated films and solutions of the polymer. The response of the absorption and the fluorescence changes of the polymer films were rapid and were reproduced more than 15 times. A lightly bound intermolecular interaction between the pyridine ligand and cation was presumed to be responsible for the facile optical switching property of the polymer films. (C) 2004 Wiley Periodicals, Inc.