In situ metallation of free base phthalocyanine covalently bonded to Si(100) and porous Si surfaces

In recent years phthalocyanine have attracted research efforts because their promising application in dye-sensitized solar cells, catalysis, cancer therapy and molecular electronics. In particular, conjucated organic molecules deposited or covalently bonded to surfaces are considered the ultimate limit of electronic devices since they may lead to hybrid heterostructures with new properties. In this communication, hybrid systems of 4-undecenoxyphthalocyanine covalently bonded to Si(100) and porous silicon have been obtained by a thermic hydrosilylation reaction. In a successive step, cobalt (II) complexation of the surface-bonded phthalocyanine was performed directly on the surface by wet chemistry. Each reaction step was studied by X-Ray photoelectron and FT IR spectroscopies. The anchoring geometry of the phthaloctanine were studied combining angle resolved XPS measurement and DFT modelling. In particular N 1s peak was showing different chemical shifts depending on the anchoring geometry and substrate interactions. The efficiency of metalation process of Si bonded phthalocyanine was evaluated from angle resolved XPS measurements. Spectra revealed that the different surface-phthalocyanine interactions observed for flat and porous substrates affected the efficiency of the “in-situ” metalation reaction. On porous silicon the cobalt complexation of the phthalocyanine ring was also confirmed by the disappearance of the band at 3250 cm–1 in the FT-IR spectra.