title: Green-to-Red Electrochromic Fe(II) Metallo-Supramolecular Polyelectrolytes Self-Assembled from Fluorescent 2,6-Bis(2-pyridyl)pyrimidine Bithiophene.
abstract: The structure and properties of metallo-supramolecular polyelectrolytes (MEPEs) self-assembled from rigid 2,6-bis(2-pyridyl)pyrimidine and the metal ions FeIIand CoIIare presented. While FeL1-MEPE (L1 = 1,4-bis[2,6-bis(2-pyridyl)pyrimidin-4-yl]benzene) is deep blue, FeL2- and CoL2-MEPE (L2 = 5,5'-bis[2,6-bis(2-pyridyl)pyrimidin-4-yl]-2,2'-bithiophene) are intense green and red in color, respectively. These novel MEPEs display a high extinction coefficient and solvatochromism. Ligand L2 shows a high absolute fluorescence quantum yield (Φf= 82%). Viscosity and static light-scattering measurements reveal that the molar masses of these MEPEs are in the range of 1 × 108g/mol under the current experimental conditions. In water, FeL1-MEPE forms a viscous gel at 20 °C (c = 8 mM). Thin films of high optical quality are fabricated by dip coating on transparent conducting indium tin oxide (ITO) glass substrate. Optical, electrochemical, and electrochromic properties of the obtained MEPEs are presented. Green to red and blue to colorless electrochromism is observed for FeL2-MEPE and FeL1-MEPE, respectively. The results show that the electrochromic properties are affected by the ligand topology. The Fe-MEPEs show a reversible redox behavior of the FeII/FeIIIcouple at 0.86 and 0.82 V versus Fc+/Fc and display an excellent redox cycle stability under switching conditions. FeL2-MEPE in its oxidized state exhibits a broad absorption band covering the near-IR region (ca. 1500 nm) due to the ligand-to-metal charge transfer transition originating due to charge delocalization in the bithiophene spacer.
authors.affiliation: Chemische Technologie der Materialsynthese, Julius-Maximilians-Universität Würzburg , Röntgenring 11, D-97070 Würzburg, Germany.
authors.forename: Sandesh
authors.initials: S
authors.lastname: Pai
authors.affiliation: Center for Nanosystems Chemistry, Institut für Organische Chemie, Universität Würzburg , Am Hubland, D-97074 Würzburg, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Moos
authors.affiliation: Center for Nanosystems Chemistry, Institut für Organische Chemie, Universität Würzburg , Am Hubland, D-97074 Würzburg, Germany.
authors.forename: Maximilian H
authors.initials: MH
authors.lastname: Schreck
authors.affiliation: Center for Nanosystems Chemistry, Institut für Organische Chemie, Universität Würzburg , Am Hubland, D-97074 Würzburg, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Lambert
authors.affiliation: Chemische Technologie der Materialsynthese, Julius-Maximilians-Universität Würzburg , Röntgenring 11, D-97070 Würzburg, Germany.
authors.forename: Dirk G
authors.identifier: http://orcid.org/0000-0003-4238-1510
authors.initials: DG
authors.lastname: Kurth