XPS of MR and Immobilized Complexes

The XPS of commercially available MR showed, in addition to the expected peaks from carbon and oxygen large amounts of tin (Fig. 8.8a) [29-31]. A closer inspection of the oxygen peak lead to the conclusion that it was tin oxide, presumably from the manufacturing process of the resin [30]. 

The supplier of the MR (Sigma-Aldrich) did not disclose any information whether tin oxide was used in the manufacturing process of this resin so the origin of this contamination is currently unknown. The resin treated with zinc(II) acetate showed only a very small amount of zinc (Fig. 8.8b) and no peaks from nitrogen. The XPS spectra of the immobilized ligands show nitrogen peaks in addition to the peaks from 

MR as expected. Also a greater degree of oxygen relative to unsubstituted resin is observed (Fig. 8.9a and b). Moreover Si 2p peaks are present in the immobilized ligand MR [31]. This is due to the fact that the resins were dried on a high vacuum oil pump and silicone oils are a known cause for this contamination [32], 

Finally the XPS spectra of the immobilized complexes showed the two typical peaks of the Zn 2p electrons (Fig. 8.10a and b) confirming the uptake of Zn(II) ions into the resin/ligand [31]. 

2p electrons displays the typical pattern with a second smaller peak at higher energy (Fig. 8.12c) [31, 33]. 

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