Molecular loops – mating cyclophanes and macrocycles

This thesis is the translation of a conceptual idea that was born years before its realization. In the autumn 2014 at a conference on molecular electronics at the University of Konstanz the discussion about single molecule transport experiments reveled around an intriguing question:

Is there a chemical design, where it is possible to distinguish between
different electronic transport pathways within one molecule?

This thesis approaches the envisaged molecular design through various publications, they are ordered such that the final structure is approached after elucidating a suitable macrocyclic structure, followed by stabilized helically chiral macrocycles, and a test system with the conductive backbone of the desired molecule. Finally, the initially planned molecule is presented.

The elucidation of the size of the macrocycle was published in Helvetica Chimica Acta, where optical investigations and the dynamic behavior of the parent macrocycle are included. Having found a suitable macrocycle, a tetrasubstituted [2.2]paracyclophane was published in the Journal of the American Chemical Society, where the detailed synthesis, chiroptical studies and the dynamic behavior of the molecule, as well as theoretical studies, are presented. Finally, single molecule conductance measurements and theoretical investigations of a molecular rod, which is the backbone of the envisaged macrocycle, have been published in Nano Letters. The last chapter then gives the synthesis of the original target compound of this thesis. The supplementary information for all chapters is given in the same order at the end of this thesis for the reader’s convenience.

Preceding these three manuscripts, the reader will find a review entitled “Beyond Simple Substitution Patterns – Symmetrically Tetrasubstituted [2.2]Paracyclophanes as 3D Functional Materials” which has been published in the European Journal of Organic Chemistry. It gives a systematic overview over the three main approaches towards symmetrically tetrasubstituted [2.2]paracyclophanes – including the substitution pattern that found application in this thesis. It integrates the topic of this thesis into the wider world of molecules that are based on [2.2]paracyclophanes with four symmetrical substituents.