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978-3-8439-0464-3, Reihe Organische Chemie
Tailoring Intra- and Intermolecular Properties: From Cyclophanes to Daisy Chains
298 Seiten, Dissertation Universität Basel (2012), Softcover, A5
The synthesis and aggregation studies of a hermaphroditic molecular rod comprising a terminal water soluble loop are presented. A mono-functionalized Diederich-type cylophane, acting as the loop subunit, containing a hydrophobic cavity was synthesized in 10 or 7 steps, respectively. Functional group transformations of this hydrophilic macrocycle and final coupling of an oligophenylene-ethynylene hydrophobic molecular rod provided the envisaged target compound in 21 or 17 synthetic steps. By dissolving this amphiphile in polar solvents the hydrophobic rod threads into the cavity of the macrocycle driven by a strong hydrophobic effect. Aggregation studies by 1H-NMR titrations, fluorescence titrations and mass spectrometry confirmed the formation of dimers at low concentrations and longer oligomers at higher concentrations. Such molecular daisy chains are potential candidates towards new polymers with altered macroscopic properties.
Towards application of such daisy chain dimers, the functionalization of the molecular rod of the amphiphilic daisy chain monomer at the terminus with thiol anchoring groups for investigations in molecular electronics is shown. Aggregation studies revealed a similar self-complexation behavior as the unfunctionalized version. Such thiol-functionalized pseudorotaxanes are potential candidates for investigations of bimolecular bridges in mechanically controlled break junctions (MCBJ) potentially resulting in a single molecular potentiometer.
In the second part of this thesis the investigations of torsion angle restricted biphenyl cyclophanes are described. By bridging the 2,2' position of the biphenyl with alkyl chains of varying length a series of biphenyls were obtained with tailored torsion angle. Topics in non-linear optics, atropisomerization and the charge injection of organic thin film transistors were addressed using such biphenyl building blocks.