1. Laboratory of Physical Chemistry, Department of Chemistry, University of Helsinki, P.O. Box 55 (A.I. Virtasen aukio 1), FIN-00014 University of Helsinki, Finland, Department of Chemistry, University of Otago, P.O. Box 56, 9054 Dunedin, New Zealand, Department of Chemistry, University of Waikato, Private Bag 3105, Hamilton 3240, New Zealand, and Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark