Dinuclear Pt and Pd complexes with metalloporphyrin bridges: A NEXAFS study of the electronic structure and self-assembling properties

Molecular and electronic structure of organometallic assemblies containing Zn-diethynylporphyrin (ZnDEP) bridged between Pt(II) and Pd(II) tethers, i.e. –Pt(PBu3)2Cl or –Pd(PBu3)2(–CC–Ph), were investigated by means of Near Edge X-ray Absorption Fine Structure spectroscopy (NEXAFS). N K-edge spectra collected on the two macromolecular arrays were compared with data on ZnDEP and diethynylporphyrin (DEP); an energy shift towards higher photon energy values was observed and attributed to charge transfer from the tetrapyrrolic macrocycle to the transition metal terminal groups. Angular dependent NEXAFS characterisation of both Pd–ZnDEP and Pt–ZnDEP films deposited on gold allowed to assess that the macromolecules grow in ordered layers.