A Fourier Transform Infrared Reflection−Absorption Spectroscopy Study of Redox Polyelectrolyte Films

Self-assembled polyelectrolyte multilayer films comprised of poly(allylamine) derivatized with an Os(bpy) 2 ClPyCH− complex (PAH−Os), and poly(vinylsulfonate), PVS, or poly(styrensulfonate), PSS, have been studied by Fourier transform infrared reflection−absorption spectroscopy. The infrared absorbances of the characteristic SO 3 -, CH 2, NH 3 +, and aromatic bipyridine and pyridine groups have been characterized, and their intensity increases with the number of self-assembled layers and redox charge. The characteristic infrared signatures are the 1040 cm - 1 band assigned to the aromatic ligands in the osmium complex (ν(Py)), PAH−Os, and the 1040 cm - 1 (ν s (SO 3 - )) and 1213 cm - 1 (ν a (SO 3 - )) bands for SO 3 groups in PVS. The ν s (SO 3 - ) vibrational mode of PVS senses the local NH 3 + environment of the cationic PAH−Os resulting in a band shift of 22 cm - 1 for the first polyallylamine layer. Subtractively normalized Fourier transform infrared spectroscopy during the oxidation of the Os centers in the (PAH−Os) n (PVS) m multilayer reveals that different vibrational modes of bipyridine ligands in the osmium redox center of PAH−Os and the sulfonate groups of PVS are affected by charge−ligand electrostatic interaction and dipole reorganization in the multilayers.