X-ray absorption spectral studies on the anion-selectivity of a ruthenium(II) polypyridine complex-impregnated polymer ultrathin film

The anion-selectivity of the surface of a polymer ultrathin film incorporating an amphiphilic ruthenium(II) polypyridine complex with diperchlorate was examined using X-ray absorption spectroscopy with the total electron-yield method. The adsorbed species on the film surface were found to depend on the chemical composition in water where the film was prepared. By combining the X-ray absorption spectra with a molecular-orbital calculation, the molar ratio (M_ClO4/M_Ru) between the ClO₄^- ions and the Ru head group on the film surface could be semi-quantitatively analyzed; it was 0.88 for a film prepared on fresh water, and 1.4 for one prepared on old water.