1. School of Chemistry, Cardiff University, PO Box 912, Cardiff CF10 3TB, United Kingdom, Centre for Polymer Therapeutics, Welsh School of Pharmacy, Redwood Building King Edward VII Avenue, Cardiff CF10 3XF, United Kingdom, ISIS Facility, Rutherford Appleton Laboratory, Chilton, Oxfordshire OX11 0QX, United Kingdom, Institut Laue-Langevin, 6 rue Jules Horowitz, Grenoble, France, and Dipartimento di Chimica Organic e Industriale, Universita' degli Studi di Milano, via Venezian 21, 20133, Milano, Italy