title: Limits of Molecular Dithienylethene Switches Caused by Ferrocenyl Substitution.
abstract: The efficiency of photochromic switches can be modified by attaching organic or organometallic groups to the photochromic core. We studied ferrocene-substituted dithienylethene switches differing by the size of the cycloalkene ring bridging the two thiophene groups. The results were compared with their chlorine-substituted counterparts and an ethynyl-ferrocene substituted switch published earlier by Guirado and co-workers. From the measured UV/Vis spectra, both ferrocene-substituted compounds were found to be considerably less likely to switch than the corresponding chlorine-substituted ones. Kohn-Sham density functional theory calculations suggested that this is due to a multitude of energetically close-lying excited states in the former, which may offer multiple pathways for excitation and relaxation, out of which only one leads to ring opening or closing. By contrast, the chlorine-substituted switches have one energetically more isolated state that is responsible for the switching. The increase in the available excited states in the ferrocene-substituted switches was attributed to mixing between orbitals from the ferrocene units and the π system of the bridge.
authors: Institut für Anorganische und Angewandte Chemie, Universität Hamburg, Martin-Luther-King-Platz 6, 20146, Hamburg, Germany.
authors: Alejandra
authors: http://orcid.org/0000-0002-2697-8627
authors: A
authors: Escribano
authors: Institut für Anorganische und Angewandte Chemie, Universität Hamburg, Martin-Luther-King-Platz 6, 20146, Hamburg, Germany.
authors: Torben
authors: T
authors: Steenbock
authors: Institut für Anorganische und Angewandte Chemie, Universität Hamburg, Martin-Luther-King-Platz 6, 20146, Hamburg, Germany.
authors: Carmen
authors: C
authors: Herrmann
authors: Institut für Anorganische und Angewandte Chemie, Universität Hamburg, Martin-Luther-King-Platz 6, 20146, Hamburg, Germany. heck@chemie.uni-hamburg.de.
authors: Jürgen
authors: http://orcid.org/0000-0001-6468-6863
authors: J
authors: Heck
keywords: UV/Vis spectroscopy; cyclic voltammetry; ferrocene; molecular switches; photochromism