School of Chemistry, University of Bristol, Bristol BS8 1TS, United Kingdom, Institut Max-von-Laue-Paul-Langevin, BP 156-X, F-38042 Grenoble Cedex, France, ISIS, Rutherford Appleton Laboratory, Chilton, Oxon OX11 0QX, United Kingdom, and Syngenta Jealott's Hill International Research Center, Bracknell, Berkshire RG42 6EY, United Kingdom (At 2006-01-17)