1. Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 København Ø, Denmark
2. Department of Natural Sciences, University of Copenhagen, Thorvaldsensvej 40, 1871 Frederiksberg C, Denmark
3. The Technical University of Denmark, The Department of Chemistry, Building 207, 2800 Lyngby, Denmark
4. Present address: Tårnby Gymnasium and HF, Tejn Allé 5, 2770 Kastrup, Denmark