X-ray photoelectron spectroscopy studies of novel Pi-conjugated ethynyl thiophene containing Pd(II) complexes and of their interaction with chromium

The structure of some novel oligomeric thiophene-containing pi-conjugated Pd(II) complexes, recently prepared in our laboratory, Cl-Pd(PBu3)(2)-C=C-C4H2S-C=C-C4H2S-C=C-C4H2S-C=C-Pd(PBu3)(2)Cl or Pd-TRI and Cl[-Pd(PBu3)(2)-C=C-C4H2S-C=C-](3)-Pd(PBu3)(2)Cl Or Pd-DET, were studied by means of x-ray photoelectron spectroscopy. The interface formation between chromium and the organometallic rr-conjugated polymer films was also investigated. Chromium was evaporated stepwise in situ onto the surface of the polymer films and the XPS core-level spectra of the polymer and of the metal overlayer were studied as a function of Cr coverage. A charge-transfer reaction from the deposited metal atoms to the substrate material was evidenced by the modifications taking place in the polymer spectra upon Cr deposition. A comparison with the surface reactivity towards chromium of [-Pd(PBu3)(2)-C=C-C6H4-C6H4-C=C-](n), Pd-DEBP, a related polymer where benzene groups replace thiophene in the organic conjugated moiety, will be discussed.