New Dyes Based on Extended Fulvene Motifs: Synthesis through Redox Reactions of Naphthoquinones with Donor–Acceptor Cyclopropanes and Their Spectroelectrochemical Behavior

• Published in: Chemistry : a European journal 2019-08, Vol.25 (44), p.10359-10365
• Main Authors: Lücht, Alexander, Sobottka, Sebastian, Patalag, Lukas J., Jones, Peter G., Reissig, Hans‐Ulrich, Sarkar, Biprajit, Werz, Daniel B.
• Format: Article
• Language: English
• Subjects: Chemical synthesis; Chemistry; donor–acceptor cyclopropanes; Dyes; Electrochemistry; Electrochromism; EPR spectroscopy; fulvene; Nucleophiles; Organic compounds; Redox reactions; spectroelectrochemistry
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201900764

Novel dyes based on extended fulvene motifs are reported. The carbon skeleton was generated by a catalyzed addition of donor–acceptor cyclopropanes to naphthoquinone. The hydroxy group at the central ring of the tricyclic fulvene motif was converted into the triflate, which reacted efficiently with a wide range of nucleophiles, resulting in substitution and thereby providing new derivatives. The synthetic versatility allowed us to investigate the absorption, electrochemical, and UV/Vis‐NIR spectroelectrochemical properties of these dyes as a function of the substituents. The dyes were shown to participate in reductive electrochemistry, the reversibility of which can be improved by appropriate selection of the substituents. Additionally, first signs of NIR electrochromism are presented, opening new avenues for the future investigations of such dyes. A library of new fulvene dyes: A simple approach to synthesize dyes containing a fulvene subunit by using donor–acceptor (D–A) cyclopropane chemistry and subsequent substitution reactions is presented. The color, reduction potentials, and reversibility of the redox processes are controlled by the choice of only one substituent. A novel D–A cyclopropane leads to extended π‐systems with a naphthalene unit.