XAS of Ruthenium Phthalocyanine Dimer : Structural Properties of Bulk and Film Form

We measured in absorption mode at the Ruthenium K-edge, Ru-Ru and Ru-N distances, in structurally known systems: the Ruthenium dimeric precursor compound, already structurally characterized, the monomeric species of Ruthenium phthalocyanine (adduct) and the polymeric species of Ruthenium phthalocyanine (with bridging oxygen). The film, a candidate for sensor and electrochromic applications, is loaded by sublimation and has been measured in fluorescence straight on the growth substrate (glass) obtaining excellent data. In the Fourier transforms obtained for the dimer, a Ru-Ru bond is well defined. For the monomer no Ru-Ru distance is present within the fit of the first neighbours while the polymeric species shows a well defined peak, at m. 3.38 A, due to the moiety Ru-0-Ru, absent in the other two cases. In the film case no evidence is present for a Ru-0-Ru bond, while it is evident that a Ru-Ru bond at 2.35 A is present at the same distance as in the dimer. Good fit of the film data are indeed obtained by imposing the dimer parameters in perfect agreement within the first two shells.