1. Istituto CNR di Chimica Biomolecolare Trav. La Crucca 3 07040 Sassari Italy
2. Dipartimento di Chimica e Farmacia Università di Sassari Via Vienna 2 07100 Sassari Italy
3. Departament de Química Universitat Autònoma de Barcelona Cerdanyola del Vallés 08193 Barcelona Spain
4. Chemical Sciences Division Lawrence Berkeley National Laboratory 1 Cyclotron Road 94720 Berkeley CA United States
5. Department of Chemistry University of California 94720 Berkeley CA United States