Determination and fine tuning of the cerium oxidation state in cerium calixarene complexes

Yuri Suchorski 1Jochen Gottfriedsen Rafal Wrobel Bartosz Strzelczyk Helmut Weiss 1

1. Otto-von-Guericke-Universitaet Magdeburg, Chemisches Institut, Universitaetsplatz 2, Magdeburg D-39106, Germany

Abstract

Interesting structures and properties as well as perspectives of practical use motivated intensive studies of various calixarene complexes in recent years. The development of new catalysts increases also the interest in the design and synthesis of supramolecular metallocalixarene arrays. The novel cerium calixarene complexes [p-tBu-calix[4](OMe)2(O)2Ce(acac)2] (1) and [p-tBu-calix[4](OMe)2(O)2Ce(hfac)2] (2) were recently synthesized in an equimolar reaction between p-tBu-calix[4](OMe)2(OH)2 and cerium complexes Ce(acac)4 (acac = acetylacetonate), and Ce(hfac)4 (hfac = 1,1,1,5,5,5-hexafluoro-acetylacetonate), respectively [1].

The cerium oxidation state in such complexes is discussed intensively, whereas contradictory results are reported [2]. In the present study, X-ray photoelectron spectroscopy (XPS) with monochromatic Al Kα excitation (1486.74 eV) was applied in a "fast transfer" mode [3]. The experiments revealed an irradiation-induced decrease of the Ceox values of both complexes dependent upon X-ray exposure. The detailed study of the dynamical response of the Ceox to X-ray irradiation allowed the determination of Ceox at "zero irradiation" [3.60 for complex (1) and 3.65 for complex (2), respectively]. Neither vacuum-induced reduction, nor re-oxidation of the irradiated compounds in air were observed suggesting the possibility of the long-lasting X-ray induced tuning of Ceox in a range of at least 3.65 to 3.26.

[1] J. Gottfriedsen, D. Dorokhin, Z. allg. anorg. Chem. 631 (2005) 2928;

[2] C. H. Booth, M. D. Walter, M. Daniel, W. W. Lukens, R. A. Andersen, Phys. Rev. Lett. 95 (2005) 267202, and references therein

[3] Y. Suchorski, L. Rihko-Struckmann, F. Klose, Y. Ye, M. Alandjiyska, K. Sundmacher, H. Weiss, Appl. Surf. Sci. 249 (2005) 231.

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Presentation: Poster at E-MRS Fall Meeting 2006, Symposium B, by Yuri Suchorski
See On-line Journal of E-MRS Fall Meeting 2006

Submitted: 2006-05-12 13:02
Revised:   2009-06-07 00:44
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