Hybrid Material Based on the Lindquist Polyoxometalate [W6O19]2− and the organosulfur donor o-Me2TTF: A Combined Structural and Spectroscopic Study

Abstract

International audienceThe synthesis, crystal structure and spectroscopic properties of the hybrid radical cation salt containing oxidized o-3,4-dimethyltetrathiafulvalene (o-Me2TTF) and the Lindquist polyoxometalate anion [W6O19]2− are reported. The title salt represents the first time a Lindquist polyoxometalate has been utilized as the counter anion with this unsymmetrical member of the TTF family of derivatives. The salt crystallizes in the triclinic space group P1¯ with a = 7.6211(7) Å, b = 9.5231(9) Å, c = 12.2148(11) Å, α = 105.5870(10)°, β = 106.8340(10)° and γ = 95.6950(10)°. Resolution of the solid state structure revealed that the o-Me2TTF radical cations aggregate as isolated face-to-face dimers with intradimer interactions between neighboring sulfur atoms at distances <3.6 Å. Hydrogen bonding was also observed between hydrogen atoms bound to sp 2-hybridized carbon atoms of o-Me2TTF and bridging oxygen atoms of [W6O19]2−. Single crystal IR and Raman spectra were also collected and provide further evidence that the o-Me2TTF donors have been oxidized to their corresponding radical cationic states

Electron-molecular vibration coupling in (DMtTTF)Br and (o-DMTTF)2[W6O19] salts studied by vibrational spectroscopy

“…These facts suggest that in some cases non-totally symmetric modes can be also coupled [19]. were the subject of our recent report [20]. …”

“…•+ cation are given in 2-was reported [20]. In this salt, the donor molecules aggregate in a head-to-tail manner, forming strong face-…”

“…6). It is important to note that by comparison, the charge transfer band of (o-DMTTF) 2 were found and assigned to the stretching of central C=C bond, as well as the out-of-phase and in-phase stretching of ring bonds respectively [20].…”

“…Much like the IR spectra for the recently published (o-DMTTF) 2 [W 6 O 19 ] whose structure contained quasi-isolated dimers [20], the IR spectra for (DMtTTF)Br can also be analyzed in terms of the isolated dimer model. For both salts, due to the coupling, the vibrational modes borrow intensity from the nearby CT electronic transition and occur at frequencies lower than their corresponding Raman bands.…”

Decoupling anion-ordering and spin-Peierls transitions in a strongly one-dimensional organic conductor with a chessboard structure, (o-Me2TTF)2NO3

“…2À (Reinheimer et al, 2013) led to insulating salts of the fully oxidized o-Me 2 TTF þ cations, associated into diamagnetic dicationic dyads (o-Me 2 TTF) 2 2+ . On the other hand, the non-centrosymmetric NO 3…”