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 02139-4307, United States
4. Department
of Chemistry, University of Texas at San Antonio, San Antonio, Texas 78249, United States