[1] Inst Super Tecn, Ctr Quim Estrutural, P-104901 Lisbon, Portugal
[2] Karl Franzens Univ Graz, Inst Chem, A-8010 Graz, Austria
[3] Univ London Imperial Coll Sci Technol & Med, London SW7 2AY, England
[4] RWTH Aachen Univ, Inst Tech & Macromol Chem, D-52074 Aachen, Germany