1. Laboratoire de Chimie-Physique, UMR 7512 au CNRS, ECPM-ULP, 25, rue Becquerel, 67087 Strasbourg, Cedex 2, France, Chemistry Department, Open University, Milton Keynes, MK7 6AA, U.K., and School of Chemistry, Queen's University, Belfast BT9 5AG, U.K.