1. Department of Chemistry, University of British Columbia, Vancouver V6T 1Y6, Canada
2. Department of Chemistry, Dalhousie University, Halifax, Nova Scotia B3H 4J3, Canada
3. BP Research Centre, Chertsey Road, Sunbury-on-Thames TW16 7LM, UK
4. Grace Service Chemicals, Foundry Lane, Widnes WA8 8UD, UK