1. Institute of Organic Chemistry, Johannes Gutenberg University of Mainz, Duesbergweg 10-14, 55128 Mainz, Germany
2. Institute of Physical Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany
3. Institute Laue-Langevin, DS/LS, 71 Avenue des Martyrs, CS 20156, 38042 Grenoble Cedex 9, France