1. Contribution from the Department of Chemistry, University of Durham, Durham DH1 3LE, U.K., L. M. Litvinenko Institute of Physical Organic and Coal Chemistry, National Academy of Sciences of Ukraine, Donetsk 83114, Ukraine, Ingénierie Moléculaire et Matériaux Organiques, CNRS UMR 6501, Université d'Angers, 49045 Angers Cedex 01, France, and the EPSRC c.w. EPR Service Centre, Department of Chemistry, The University of Manchester, Manchester MI3 9PL, U.K.