We report electrochemical quartz crystal microbalance (EQCM) results for electrodeposition of titanocene derivatized polypyrrole p(Tc3Py) films and redox transformation of polypyrrole matrix and titanocene centers immobilized in the film. Films of p(Tc3Py), Tc3Py = Tc(CH2)(3)NC4H4 (Tc = Cl2TiCpCp', CP = C5H5, CP' = C5H4) Were obtained from acetonitrile solutions of monomer on a Pt disc or thin Au layer evaporated on 10 MHz quartz crystals. Polymerization efficiency, derived from the slope of the change of resonant frequency as a function of the deposition charge ranged from 54% to 75%. A gradual loss of redox activity of Tc centers during consecutive redox cycles of p(Tc3Py) film in TBAFP(6)/THF solutions is discussed in terms of elimination of Cl- ions from the Tc complex and accommodation of solvent molecule. The EQCM data are supported by XPS results. The preliminary studies performed in TEACl in AN solution have shown that the presence of Cl- ions in the solution markedly inhibits the loss of redox activity of Tc centers immobilized in the polymer matrix. (C) 2004 Elsevier Ltd. All rights reserved.