1. Contribution from the Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, Department of Chemistry, University of Gdańsk, Sobieskiego 18, 80-952 Gdańsk, Poland, Institute of Organic Chemistry and Biochemistry, The Academy of Sciences of the Czech Republic (ASCR), Flemingovo nám.2, 166 10 Prague 6, Czech Republic, and Chemical Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352