• Tetrathiafulvalene-1,3,5-triazines as (Multi)Donor-Acceptor Systems with Tunable Charge Transfer: Structural, Photophysical, and Theoretical Investigations
    F. Pop, F. Riobé, S. Seifert, T. Cauchy, J. Ding, N. Dupont, A. Hauser, M. Koch and N. Avarvari
    Inorganic Chemistry, 52 (9) (2013), p5023-5034
    DOI:10.1021/ic3027336 | unige:27865 | Abstract | Article HTML | Article PDF
Palladium-catalyzed cross-coupling reactions between chlorinated 1,3,5-triazines (TZ) and tetrathiafulvalene (TTF) trimethyltin derivatives afford mono- and C3 symmetric tris(TTF)-triazines as donor–acceptor compounds in which the intramolecular charge transfer (ICT) is modulated by the substitution scheme on TTF and TZ and by chemical or electrochemical oxidation. The TTF-TZ-Cl2 and (SMe)2TTF-TZ-Cl2 derivatives show fully planar structures in the solid state as a consequence of the conjugation between the two units. Electrochemical and photophysical investigations, supported by theoretical calculations, clearly demonstrate that the lowest excited state can be ascribed to the intramolecular charge transfer (ICT) π(TTF)→π*(TZ) transition. The tris(TTF) compound [(SMe)2TTF]3-TZ shows fluorescence when excited in the ICT band, and the emission is quenched upon oxidation. The radical cations TTF+• are easily observed in all of the cases through chemical and electrochemical oxidation by steady-state absorption experiments. In the case of [(SMe)2TTF]3-TZ, a low energy band at 5000 cm–1, corresponding to a coupling between TTF+• and TTF units, is observed. A crystalline radical cation salt with the TTF-TZ-Cl2 donor and PF6– anion, prepared by electrocrystallization, is described.
  • Tetrathiafulvalene-Benzothiadiazoles as Redox-Tunable Donor-Acceptor Systems: Synthesis and Photophysical Study
    F. Pop, A. Amacher, N. Avarvari, J. Ding, L.M. Lawson Daku, A. Hauser, M. Koch, J. Hauser, S.-X. Liu and S. Decurtins
    Chemistry - A European Journal, 19 (7) (2013), p2504-2514
    DOI:10.1002/chem.201202742 | unige:26401 | Abstract | Article PDF
Electrochemical and photophysical analysis of new donor–acceptor systems 2 and 3, in which a benzothiadiazole (BTD) unit is covalently linked to a tetrathiafulvalene (TTF) core, have verified that the lowest excited state can be ascribed to an intramolecular-charge-transfer (ICT) π(TTF)→π*(benzothiadiazole) transition. Owing to better overlap of the HOMO and LUMO in the fused scaffold of compound 3, the intensity of the 1ICT band is substantially higher compared to that in compound 2. The corresponding CT fluorescence is also observed in both cases. The radical cation TTF+. is easily observed through chemical and electrochemical oxidation by performing steady-state absorption experiments. Interestingly, compound 2 is photo-oxidized under aerobic conditions.



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