1 Stratingh Institute for Chemistry, Center for Systems Chemistry and Zernike Institute for Advanced Materials, Faculty of Mathematics and Natural Sciences, University of Groningen, Groningen, the Netherlands. m.p.k.kathan@rug.nl.
2 Stratingh Institute for Chemistry, Center for Systems Chemistry and Zernike Institute for Advanced Materials, Faculty of Mathematics and Natural Sciences, University of Groningen, Groningen, the Netherlands.
3 Institut für Chemie und Biochemie der Freien Universität Berlin, Berlin, Germany.
4 Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany.
5 Macromolecular Chemistry and New Polymeric Materials and Zernike Institute for Advanced Materials, Faculty of Mathematics and Natural Sciences, University of Groningen, Groningen, the Netherlands.
6 Institut für Chemie und Biochemie der Freien Universität Berlin, Berlin, Germany. c.schalley@fu-berlin.de.
7 Stratingh Institute for Chemistry, Center for Systems Chemistry and Zernike Institute for Advanced Materials, Faculty of Mathematics and Natural Sciences, University of Groningen, Groningen, the Netherlands. b.l.feringa@rug.nl.