1. Contribution from the Eenheid Algemene Chemie, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium, Faculty of Chemical Engineering, HoChiMinh City University of Technology, HoChiMinh City, Vietnam, Faculty of Chemistry, University of Danang, Danang, Vietnam, and Department of Chemistry, University of Leuven, Celestijnenlaan, 200 F, B-3001 Leuven, Belgium