1. Materials Chemistry Centre, Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K.
2. Laboratory of Inorganic Chemistry, Environmental and Chemical Engineering, University of Oulu, P.O.
Box 3000, Oulu FI-90014, Finland
3. Faculty of Mathematics and Physics, Charles University, Ke Karlovu 5, Prague 2 121 16, Czech Republic