Molecular orientation of thiol-derivatized tetraphenylporphyrin on gold studied by XPS and NEXAFS

Surface chemistry of porphyrins and phthalocyanines

“…The molecular plane was then tilted by 381 relative to the substrate. For de-acetylation on the substrate, only two thiol bonds per molecule were observed on average and the tilt angle was 501 [449]. Similar studies with tetraphenylporphyrins derivatized with one and four thiol anchors have also been performed by others [445].…”

“…Covalent tethering of porphyrins to metal surfaces through reactive anchoring groups at the periphery of the molecules was performed with protoporphyrin IX (2HPPIX, Fig. 4c) [443,444] and with various other porphyrins using anchor groups on the basis of thiols [445], disulfides [446], acetylthiols [447][448][449][450][451], and others [452,453]. In some cases, electronic decoupling from the (metal) substrate was desired, for example to avoid quenching of excited states by substrate influences in the context of photochemistry.…”

Porphyrins as Active Components for Electrochemical and Photoelectrochemical Devices

“…Instead, several groups have reported strong evidence for the incomplete binding of the sulfur atoms of the side chains to the surface, thus detecting unexpected tilted orientations. [89][90][91][92][93] XPS is probably the most important technique to clarify the nature of sulfur atoms of the side chains. Indeed S 2p spectra of bound (to gold) and unbound sulfur atoms give raise to characteristic peaks at about 162.0 and 163.5 eV respectively.…”

“…Watchrinyanon et al showed that an average of three sulfurs out of four of meso-tetra-[p- (3-mercaptopropyloxy)phenyl]porphyrin (and its cobalt complex) were able to bind the surface, while the last linker was dangling outward (Figure 9). 90 Furthermore, the same porphyrin with thioacetyl-protected sulfurs could be attached with an average of 2.5 sulfurs. Near Edge X-Ray Absorption Fine Structure (NEXAFS) experiments supported the idea that the porphyrin was bound to the surface through two adjacent legs.…”

Gold nanoparticles decorated on Bingel–thiol functionalized multiwall carbon nanotubes as an efficient and robust catalyst

“…The S2p spectrum of material MWCNT_SH shows two doublets, the most abundant with S2p 3/2 at 164.0 eV ascribed to unbounded SH groups and a minor doublet with S2p 3/2 at 168.5 eV ascribed to oxidized sulfur, probably in the form of sulfonate groups [46]; the corresponding peaks for S2p 1/2 are not reported on Table 2. Upon AuNPs deposition this latter peak slightly increased on material MWCNT_SH@Au relatively to its precursor (21% vs 15%, entries 10-11), indicating that during the deposition procedure, some oxidation of the free thiol groups is observed alongside with gold reduction.…”