1. Department of Chemistry and Center for Theoretical and Computational Chemistry, University of Tromsø, N-9037 Tromsø, Norway
2. Department of Chemistry, University of the Free State, 9300 Bloemfontein, Republic of South Africa
3. Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
4. Department of Biological, Chemical, and Physical Sciences, Roosevelt University, Chicago, Illinois 60605