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    Quasi-metallic bandgap tunability at low static pressures and quintuple chromism by electron transfer in a viologen-derivative iodide
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    In electroreduction, after the transfer of the first electron to methyl viologen, MV2+, resulting in formation of the radical cation, MV˙+, the electron transfer to MV˙+ without chemical complications occurs only under special conditions: the species more readily reduced than MV˙+ are the dication or monocation dimers, MV22+ or MV2˙+, formed in reactions in solution near the electrode.
    Dication
    Viologen
    Radical ion
    Citations (38)
    Compounds containing a viologen linked to a porphyrin via a number (n= 4–7) of methylene groups have been synthesized and photoinduced long-range electron transfer between porphyrin and viologen was observed. The photoexcited singlet state of the porphyrin was quenched by the bonded viologen in viologen-linked porphyrins. The fluorescence decay profiles of the viologen-linked porphyrins consist of a sum of two first-order decays with shorter and longer lifetimes. The shorter lifetime arises from the direct quenching of the photoexcited singlet state of the porphyrin by the linked viologen. The intramolecular electron transfer process from the porphyrin to the bonded viologen becomes less effective when the methylene chain length becomes longer.
    Viologen
    Methylene
    Photoinduced electron transfer
    Citations (20)
    Organic materials have gained considerable attention for electrochromic (EC) applications owing to improved EC performance and good processability. As a class of well-recognized organic EC materials, viologens have received persistent attention due to the structural versatility and property tunability, and are major active EC components for most of the marketed EC devices. Over the past two decades, extensive efforts have been made to design and synthesize different types of viologen-based materials with enhanced EC properties. This review summarizes chemical structures, preparation and EC properties of various latest viologen-based electrochromes, including small viologen derivatives, main-chain viologen-based polymers, conjugated polymers with viologen side-chains and viologen-based organic/inorganic composites. The performance enhancement mechanisms are concisely discussed. The current marketed viologens-based electrochromic devices (ECDs) are briefly introduced and an outlook on the challenges and future exploration directions for viologen-based materials and their ECDs are also proposed.
    Viologen
    Electrochromic devices
    Citations (163)
    Novel redox active dithiols containing the viologen (4,4′-bipyridinium group) have been synthesised. Monolayers and multilayers consisting of alternating layers of the dithiol and gold nanoparticles have been self-assembled on a gold substrate and visualised using SPM. Such materials have been investigated for their electroactivity and their ability to mediate electron transfer to an external redox couple, [Ru(NH3)6]3+/2+, in aqueous solution. Viologen moieties in these multilayers are addressable electrochemically provided they are within 6–8 layers of the external surface and it is shown that electron transfer through the deeper layers is very facile as a consequence of the presence of partially filled viologen π-orbitals. When the viologen containing dithiol is present in the outer layer, a diode effect is observed; electron transfer from the multilayer to the external couple takes place, but the reverse electron transport is inhibited.
    Viologen
    Dithiol
    Citations (103)