Mogens Brøndsted Nielsen
University of Copenhagen, Denmark.
Title: Tetrathiafulvalene-fused radiaannulenes and ï°-extended tetrathiafulvalenes -towards new electrochromic materials
Biography
Biography: Mogens Brøndsted Nielsen
Abstract
Radiaannulenes (RAs) are cyclic molecules with both exo and endocyclic double bonds and are hence structurally between radialenes and annulenes. Due to their quinoid-like structure, they are potentially Wurster-type redox systems, which gain aromaticity upon reduction. We have combined one radiaannulene with the Weitz-type redox system tetrathiafulvalene (TTF), which gains aromaticity upon oxidation as 1,3-dithiolium rings are formed. TTF-functionalized radiaanulenes were prepared from tetraethynylethene and TTF-diiodide derivatives using Pd-catalyzed coupling reactions. Electrochemical investigations showed both reversible oxidations and reductions (in sequential one-electron steps), and the optical properties of the oxidized and reduced species were investigated by spectroelectrochemistry. The distinct optical properties of each redox state of these molecules make then interesting in the development of electrochromic materials. The synthesis and optical properties of various ï°-extended TTFs, which can exist in different redox states, will also be presented, including molecules with an indenofluorene core.
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