1. Radboud University Nijmegen, Institute for Molecules and Materials, Heyendaalseweg 135, 6525 AJ Nijmegen, the Netherlands, DSM Innovative Synthesis BV, PO Box 18, 6160 MD Geleen, the Netherlands, Syncom BV, Kadijk 3, 9747 AT Groningen, the Netherlands, and Agfa-Gevaert N.V., Septestraat 27, B-2640 Mortsel, Belgium