1. Laboratory of Inorganic Chemistry, Department of Chemistry, P.O. Box 55, FIN-00014, University of Helsinki, Finland
2. Department of Chemistry, University of Joensuu, P.O. Box 111, FIN-80101 Joensuu, Finland
3. Laboratory of Polymer Technology, Helsinki University of Technology, P.O. Box 6100, FIN-02015 HUT, Finland