1. Department of Chemistry, Dalhousie University, Halifax, Nova Scotia, B3H 4J3, Canada, Department of Chemistry, University of New Brunswick, Fredericton, New Brunswick, E3B 6E2, Canada, Department of Chemistry, University of Warwick, Coventry CV4 7AL, West Midlands, U.K., and Department of Chemistry, University of Edinburgh, King's Buildings, West Mains Road Edinburgh, EH9 3JJ, Scotland