Controlled alignment and self-assembly of molecular wires is one of the challenges in the field of molecular electronics. Here, we take an approach by which two oligo(phenyleneethynylene)s (OPEs) are linked together through one vinylogous linker. These molecules thus incorporate a central stilbene part from which the two OPE wires propagate in a so-called "H-cruciform"-like motif. Each ring of the central stilbene unit also contains a redox-active dithiafulvene (DTF) unit and this part of the molecule can thus be considered as an extended tetrathiafulvalene (TTF). Here, we present how such H-cruciforms based on OPE3 and OPE5 molecular wires are prepared by Sonogashira coupling reactions and how the OPEs are functionalized with thioester end-caps as potential electrode anchoring groups. The optical and redox properties of these molecules are also presented. Unsymmetrical systems are achieved by subjecting a differentially protected diethynyl-substituted derivative of terephthalaldehyde to a phosphite-mediated coupling reaction in the presence of a 1,3-dithiol-2-thione. This reaction forms the central stilbene-extended TTF with alkyne substituents and relies on an "umpolung" of the para substituents from electron-withdrawing CHO groups to electron-donating DTF groups in a conversion also promoted by the phosphite.
European Journal of Organic Chemistry, 2017, Vol 2017, Issue 9, p. 1253-1261