1. Department of Chemistry, Stanford University, Stanford, California 94305-5080, United States
2. Scuola Superiore Meridionale, Largo San Marcellino 10, Napoli 80138, Italy
3. Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Via Cintia, Napoli I-80126, Italy
4. IBM Research-Almaden, 650 Harry Road, San Jose, California 95120, United States