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 SO3-, CH2, NH3+, 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 (nu(Py)), PAH-Os, and the 1040 cm(-1) (nu(s)(SO3-)) and 1213 cm(-1) (nu(a)(SO3-)) bands for SO3 groups in PVS. The nu(s)(SO3-) vibrational mode of PVS senses the local NH3+ environment ofthe 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 ofthe Os centers in the (PAH-Os)n(PVS). 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.