1. Department of Chemistry, Biology and Biotechnology, University of Perugia, 06123 Perugia, Italy
2. Department of Mechanical Engineering, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu-shi, Shiga 525-8577, Japan
3. Department of Chemistry, Brandeis University, Waltham, Massachusetts 02454-9110, USA