Photofunctional Conductors Based on TTF‐BODIPY Dyads Bearing p ‐Phenylene and p ‐Phenylenevinylene Spacers

Autor: Keijiro Tsujimoto, Hideki Fujiwara, Takahiro Nakagawa, Reiko Ogasawara
Rok vydání: 2014
Předmět:
Zdroj: European Journal of Inorganic Chemistry. 2014:3960-3972
ISSN: 1099-0682
1434-1948
DOI: 10.1002/ejic.201400103
Popis: This paper describes the syntheses, crystal structure analyses and physical properties of new D–A dyads containing tetrathiafulvalene (TTF) and 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) moieties linked by a p-phenylene or p-phenylenevinylene spacer for the development of photoresponsive organic conducting materials that can show photofunctionality in the visible region. The absorption spectra of the synthesized dyads recorded in CHCl3 show strong absorptions at 505 nm originating from the BODIPY moiety and weak charge-transfer absorptions at around 550 nm. The fluorescence corresponding to the BODIPY moiety was suppressed to less than half in all the dyads, which suggests the formation of photoinduced charge-transfer states. All the thin-film samples of the dyads spin-coated onto ITO-coated glass substrates exhibited electric current generation that are related to the absorption spectra of the thin films. In the crystalline samples of three dyads, the TTF moieties formed 1D conducting columns through the dimerization of the TTF moieties and relatively strong side-by-side interactions between neighbouring stacking columns. All the neutral crystals exhibited photoinduced conductivity along the stacking direction of the TTF moieties and the crystal with the weakest dimerization and the strongest side-by-side interaction showed the greatest photoconductivity of the three crystals. The PF6 salt of the dyad with a p-phenylene spacer and a 2:1 stoichiometry of the dyad and anion exhibited semi-conducting behaviour with a conductivity of 3.0 × 10–4 S cm–1 at room temperature and an activation energy of 0.18 eV, probably because this crystal has a half-filled Mott insulating band structure that originates from strongly dimerized intermolecular interactions. Upon photoirradiation, this salt showed a slight enhancement of conductivity.
Databáze: OpenAIRE
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