SURFACE AND BULK: ARE THEY ALWAYS THE SAME? X-RAY PHOTOELECTRON SPECTROSCOPY STUDY

Tatyana Bendikov 1 Delina Barats-Damatov 2 Burkhard Butschke 2 Jonathan Bauer 2 Juan Pellegrino Morono 2 Thomas Zell 2 Ronny Neumann 2 David Milstein 2
1Chemical Research Support, Weizmann Institute of Science, Rehovot
2Organic Chemistry, Weizmann Institute of Science, Rehovot

X-ray Photoelectron Spectroscopy (XPS) is a surface sensitive technique (top 10-15 nm) with sensitivity down to single atomic layer. XPS provides unique information about elemental composition and on the chemical and electronic state of the element in the material. The importance of XPS analysis is essential when the top surface and bulk of the material are different in chemical composition and, consequently, in their properties.

We present here two systems where XPS analysis shows significant differences in elemental composition of the top surface, compared to bulk material characterized by various analytical techniques, such as X-ray crystallography, NMR, EPR, Raman and infrared (IR) spectroscopies, etc.

In the first system, influence of temperature on the crystal packing and secondary structure of phosphovanadomolybdic acid, H5PV2Mo10O40 was studied.1 After high temperatures treatment (400-600°C) XPS analysis reveals enrichment of the top surface of the H5PV2Mo10O40 by amorphous vanadate/phosphate layer.

In the second system, series of iron-PNN complexes were synthesized and characterized in terms of their stability, elemental composition and metal center oxidation state.2-3 Using example of two complexes, [(tBuPNN)Fe(NO)2]+[BF4]- and [(tBuPNN)Fe(NO)­2]2+2[BF4]-, PNN= 2-[(Di-tert-butylphosphinomethyl)-6-diethylaminomethyl)pyridine, it is shown by XPS study that NO ligands are not stable and easily escape from the complex. This reveals changes in structure and in paramagnetic/diamagnetic behavior of these complexes.

  1. Barats-Damatov D., Shimon L.J., Feldman I., Bendikov T., Neumann R. Inorg. Chem. 2015, 54, 628-634.
  2. Zell T., Milko P., Fillman K.L., Diskin-Posner Y., Bendikov T., Iron M.A., Leitus G., Ben-David Y., Neidig M.L., Milstein D. Chem. Eur. J. 2014, 20, 4403-4413.
  3. Butschke B., Fillman K.L., Bendikov T., Shimon L.J., Diskin-Posner Y, Leitus G., Gorelsky S.I., Neidig M.L., Milstein D. Inorg. Chem. 2015, 54, 4909-4926.








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