In situ metalation of free base phthalocyanine covalently bonded to silicon surfaces

Abstract

SummaryFree 4-undecenoxyphthalocyanine molecules were covalently bonded to Si(100) and porous silicon through thermic hydrosilylation of the terminal double bonds of the undecenyl chains. The success of the anchoring strategy on both surfaces was demonstrated by the combination of X-ray photoelectron spectroscopy with control experiments performed adopting the commercially available 2,3,9,10,16,17,23,24-octakis(octyloxy)-29H,31H-phthalocyanine, which is not suited for silicon anchoring. Moreover, the study of the shape of the XPS N 1s band gave relevant information on the interactions occurring between the anchored molecules and the substrates. The spectra suggest that the phthalocyanine ring interacts significantly with the flat Si surface, whilst ring–surface interactions are less relevant on porous Si. The surface-bonded molecules were then metalated in situ with Co by using wet chemistry. The efficiency of the metalation process was evaluated by XPS measurements and, in particular, on porous silicon, the complexation of cobalt was confirmed by the disappearance in the FTIR spectra of the band at 3290 cm−1 due to –NH stretches. Finally, XPS results revealed that the different surface–phthalocyanine interactions observed for flat and porous substrates affect the efficiency of the in situ metalation process.

29,31-H Phthalocyanine Covalently Bonded Directly to a Si(111) Surface Retains Its Metalation Ability

“…The higher intensity of the 398.8 eV signal can be explained by the intermolecular interactions because the signal we measured is from the surface of a powder sample instead of a single H 2 Pc molecule. This observation is also consistent with previously reported explanations of these spectral features. − Finally, the presence of a low-intensity peak at approximately 402.1 eV can be explained by the formation of the Si–N bond following the deprotonation of the pyrrole nitrogen atoms. , …”

“…However, the most stable and well-defined interfaces have been produced by making covalent bonds between phthalocyanine and solid substrates by different methods, such as chemical vapor deposition in ultra-high vacuum (UHV), ligand exchange reactions, and hydrosilylation. − Among these approaches, hydrosilylation schemes are commonly used for producing stable dye-containing organic monolayers on silicon substrates based on Si–C bonds. − Furthermore, the physical and chemical properties of the resulting dye functionality can be altered by using various M-Pc (Cu, Co, Fe, Zn, etc.) with differently modified silicon surfaces, thus making a wide range of applications possible by design. , Even self-metalation processes following the deposition of modified H 2 Pc on metal and semiconductor surfaces have been reported. , However, the intrinsic limitation of this general approach is the common necessity to use an organic linker to attach the dye molecule to the surface, which may alter chemical and physical properties of the resulting interface . To have a better control and understanding of the interface between the H 2 Pc molecules and silicon surface, a direct covalent attachment without the use of additional linkers is desired.…”

“…11,23 Even self-metalation processes following the deposition of modified H 2 Pc on metal and semiconductor surfaces have been reported. 24,25 However, the intrinsic limitation of this general approach is the common necessity to use an organic linker to attach the dye molecule to the surface, which may alter chemical and physical properties of the resulting interface. 1 To have a better control and understanding of the interface between the H 2 Pc molecules and silicon surface, a direct covalent attachment without the use of additional linkers is desired.…”

Surface chemistry of porphyrins and phthalocyanines

“…The "click" cycloaddition was also employed in the context of electrocatalysis to bind Co porphyrins with peripheral acetylene groups to azide groups anchored on a diamond surface [453]. Tethering on Si(1 0 0) was achieved via hydrosilylation using triallyl tripod anchor groups [452] or long alkyle side chains with terminal double bonds [463]. Oxidized Si(1 0 0) was functionalized with 4-(ClCH 2 )-C 6 H 4 -SiCl 3 , and then a tetrapyridylporphyrin was linked to the Ar-CH 2 -Cl moieties by quaternization, resulting in densely packed structures of upright-standing molecules [464].…”

Self‐Assembly of TbPc2 Single‐Molecule Magnets on Surface through Multiple Hydrogen Bonding

“…The C 1s region (Figure b, bottom left) of TbPc 2 ‐UPy • NaPy@Si shows only little differences compared to NaPy@Si . The typical C components of the Pc rings (pyrrole carbons at 286.5 eV and its shake‐up at 288.5 eV) overlap with C components of NaPy moiety. However, we notice that a low band at 299.3 eV is evidenced, diagnostic of the presence of ureidic carbon atoms in the UPy chain (Table S2, Supporting Information).…”