In a series of three TTF-derived dicyanofluorene charge transfer complexes, an increase of the intermolecular charge transfer has been observed for both addition of nitro groups and a suitable symmetry of the fluorene skeleton. A numerical calculus of the charge transfer was based on IR spectroscopy data with respect to the stretching absorption band of the nitrile group.
Contribution dédiée au Professeur Francis Sécheresse, à l'occasion de ses 60 ans
RésuméDeux phases polymorphes, ␣ et b, pour le complexe à transfert de charge (TTF) 3 (TNF) 2 , où TTF = tétrathiofulvalène et TNF = 2,4,7-trinitro-9-fluorénone, ont été caractérisées par diffraction des rayons X et spectroscopie infrarouge. Un changement structural de la TNF conduit à des structures d'empilement distinctes. Une estimation du degré de transfert de charge établit que d b > d ␣ ≈ 0, ce qui est en accord avec les structures cristallines.
A series of metal containing organic compounds of the M[HNAFIN], . 2TCNQ-type, being M either Ni, Pd, Pt, Cu or Zn, have been prepared and studied in respect to infrared absorption spectra. Characteristic IR absorption spectra for each of the compounds are manifest, depending on the nature of the metal introduced. In particular is the C = N stretch mode absorption spectrum for Ni-containing compounds rather sharp and single peaked, while Pt and Zn containing compounds present more complex features.
A series of 1:1 organic complexes has been synthesized by reaction between TTF (tetrathiafulvalene) and three 9dicyanomethylenefluorene derivatives: 9-dicyanomethylene-2,7-dinitrofluorene (DDF), 9-dicyanomethylene-2,4,7trinitrofluorene (DTF) and 9-dicyanomethylene-4,5,7-10 trinitrofluorene-2-carboxylic acid (DC2TF). The following formulas were determined by X-ray diffraction and elemental analysis for these complexes: (TTF-DDF).CH 3 CN (1), (TTF-DDF).0.5PhCl(
2), (TTF-DTF).CH 3 CN (3), (TTF-DTF).0.5Me 2 CO (4) and (TTF-DC2TF).H 2 O (5). A sixth15 solvated compound was also obtained, with a different stoichiometry, (TTF) 3 (DC2TF) 2 .2CH 3 CN (6). The degree of charge transfer in 1-5 was estimated by IR and Raman spectroscopy. Lattice solvent, acetonitrile, chlorobenzene, or acetone, is slowly released from crystals of complexes 1-4, 20 inducing a significant decrease of the charge transfer over time. These crystals converge over months towards materials close to the neutral state. Hydrate 5 is air-stable, and displays a degree of charge transfer, = . ૡ ܍ ି , close to the range of semi-conducting or metallic organic complexes. Finally, 25 compound 6 is an ionic crystal, and is thus expected to be an insulating material. 65 ߜ = 2ሺΔߥ ߥ ⁄ ሻ 1 − ሺߥ ଵ ߥ ⁄ ሻ ଶ where ߥ and ߥ ଵ are the vibrational frequencies for neutral (ߜ = 85 0) and ionized (ߜ = 1) component, respectively, and ∆ߥ =A series of solvated donor-acceptor organic complexes was shown to slowly release lattice solvent, while the degree of charge transfer decreases steadily. This behavior is not observed in the case of a hydrate.
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