1. Organic Chemistry and Physical Chemistry, Center of Molecular Devices, Royal Institute of Technology, Teknikringen 30, 10044 Stockholm, Sweden, Laboratory for Photonics and Interfaces, Institute of Chemical Sciences and Engineering, School of Basic Sciences, Swiss Federal Institute of Technology, CH-1015 Lausanne, Switzerland, and Istituto CNR di Scienze e Tecnologie Molecolari (ISTM), c/o Dipartimento di Chimica, Università di Perugia, Via Elce di Sotto 8, I-06123, Perugia, Italy