1. Contribution from the Department of Chemistry, The University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom, Department of Chemistry, University of Florida, Gainesville, Florida 32611-7200, CCLRC Daresbury Laboratory, Daresbury, Warrington, Cheshire, WA4 4AD, United Kingdom, Laboratoire Louis Néel-CNRS, 38042 Grenoble, Cedex 9, France, and School of Chemistry, The University of Edinburgh, West Mains Road, Edinburgh, EH9 3JJ, United Kingdom