Platinum complex/Zn-porphyrin macrosystem assemblies: Electronic structure and conformational investigation by x-ray photoelectron spectroscopy

In this study we used x-ray photoelectron spectroscopy (XPS) to characterize newly synthesized platinum/zinc-porphyrin assemblies. Our investigation provides information both on the electronic structure and on the composition and conformation of the linked systems. In particular, the N is and Pt 4f(7/2,5/2) spectra reveal the presence of a charge transfer interaction between the two subunits in which the charge flows from the Zn-porphyrin towards the platinum unit. Analysis of the: Cl 2p(3/2) core level electrons has led to a greater understanding of the conformational structure of these systems, verifying the occurrence of cis-trans isomerization from the pristine platinum complex to the linked assemblies, or the persistence of the conformation of the precursor platinum complex. We used XPS quantitative evaluation of the atomic ratios to estimate the subunit ratio between the Zn-porphyrinato and the Pt complex and also identified a platinum linked tetramer. The XPS results are consistent with nuclear magnetic resonance, infrared and matrix assisted laser desorption ionization spectroscopy.