1. Molecular Photonic Materials, van't Hoff Institute for Molecular Sciences, Universiteit van Amsterdam, Nieuwe Achtergracht 166, 1018 WS Amsterdam, The Netherlands, Institut für Organische Chemie, Universität Regensburg, D-93040 Regensburg, Germany, Vrije Universiteit, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands, and Dipartimento di Chimica “G. Ciamician”, University of Bologna, via Selmi 2, I-40126 Bologna, Italy