Synthesis and applications of tetrathiafulvalenes and ferrocene-tetrathiafulvalenes and related compounds

A Dibenzotetrathiafulvalene-Bridged Bis(alkenylruthenium) Complex and Its One- and Two-Electron-Oxidized Forms

We report on the synthesis of the new bis(alkenylruthenium) complex DBTTF-(ViRu)2 with a longitudinally extended, π-conjugated dibenzotetrathiafulvalene (DBTTF) bridge, characterized by multinuclear NMR, IR, and UV/vis spectroscopy, mass spectrometry, and single-crystal X-ray diffraction. Cyclic and square-wave voltammetry revealed that DBTTF-(ViRu)2 undergoes four consecutive oxidations. IR, UV/vis/near-IR, and electron paramagnetic resonance spectroscopy indicate that the first oxidation involves the redox-noninnocent DBTTF bridge, while the second oxidation is biased toward one of the peripheral styrylruthenium entities, thereby generating an electronically coupled mixed-valent state ({Ru}-CH═CH)•+-DBTTF•+-(CH═CH-{Ru}) [{Ru} = Ru(CO)Cl(PiPr3)2]. The latter is apparently in resonance with the ({Ru}-CH═CH)•+-DBTTF-(CH═CH-{Ru})•+ and ({Ru}-CH═CH)-DBTTF2+-(CH═CH-{Ru}) forms, which are calculated to lie within 19 kJ/mol. Higher oxidized forms proved too unstable for further characterization. The reaction of DBTTF-(ViRu)2 with the strong organic acceptors 2,3-dichloro-5,6-dicyano-1,4-benzoquinone, tetracyano-p-benzoquinodimethane (TCNQ), and F4TCNQ resulted in formation of the DBTTF-(ViRu)2•+ radical cation, as shown by various spectroscopic techniques. Solid samples of these compounds were found to be highly amorphous and electrically insulating.

Sigmatropic Rearrangement-Based Synthesis of 4-Alkenyl-1,3-dithiol-2-ones

A series of conjugated 4-alkenyl-1,3-dithiol-2-ones have been prepared by microwave-assisted rearrangement of S-(4-acyloxy-2-alkynyl)- O-ethyl xanthates in moderate to good yields. The synthetic approach is based on a combination of [3,3] and [1,5] sigmatropic rearrangements as well as the intermediacy of a reactive betaine that induces the ionic elimination of the acyloxy group. The [1,5] sigmatropic rearrangement was confirmed by a deuterium-labeling experiment.

Selective Functionalization of Tetrathiafulvalene Using Mg- and Zn-TMP-Bases: Preparation of Mono-, Di-, Tri-, and Tetrasubstituted Derivatives

The tetrathiafulvalene-scaffold (TTF) reacts selectively in allylation, acylation, arylation, halogenation, and thiolation reactions via magnesium or zinc derivatives that are obtained by a direct metalation with Mg- and Zn-TMP-bases (TMP = 2,2,6,6-tetramethylpiperidyl). This stepwise functionalization provides access to a range of new mono-, di-, tri-, and tetra-functionalized TTF-derivatives and allows for fine-tuning of their energy levels.

Current advances in fused tetrathiafulvalene donor–acceptor systems

Development and applications of tetrathiafulvalene-fused electron donor–acceptor systems will be covered within this tutorial review.

Structures and properties of a BEDT-TTF-based organic charge transfer salt and the zwitterion of ferrocenesulfonate

The structure and properties of a new semiconducting BEDT-TTF-based charge-transfer salt containing the ferrocenesulfonate (Fc-SO3(-)) anion, α-(BEDT-TTF)2Fc-SO3·2.5H2O, are described. The structure and magnetic properties of a zwitterion of ferrocenesulfonate, Fc(+)-SO3(-), are also reported.

Ferrocene-dithiolene hybrids: control of strong donor-acceptor electronic communication to reverse the charge transfer direction

We prepared a novel class of ferrocene-dithiolene hybrid molecules, FcS4dt(Me)2 and FcS4dt[Pt((t)Bu2bpy)] (where FcS4dt indicates 2-(1,3-dithia[3]ferrocenophane-2-ylidene)-1,3-dithiole-4,5-dithiolate and (t)Bu2bpy indicates 4,4'-di-tert-butyl-2,2'-bipyridine), in which the ferrocene moiety was bound to the planar conjugated dithiolene skeleton via two sulfur atoms such that the cyclopentadienyl rings were perpendicular to the dithiolene backbone. The physical properties and electronic structures of the complexes and their oxidized species [FcS4dt(Me)2](•+) and [FcS4dt[Pt((t)Bu2bpy)]](•+) were investigated by means of single-crystal X-ray diffraction (XRD) analysis, cyclic voltammetry, electron paramagnetic resonance (EPR), and UV-vis near infrared (UV-vis-NIR) spectroscopy. The electron density distributions of the highest occupied molecular orbitals (HOMOs) of FcS4dt(Me)2 and FcS4dt[Pt((t)Bu2bpy)] differed remarkably in that the HOMO of the former was ferrocene-based whereas that of the latter was dithiolene-based. The differences in the HOMO distributions originated from the energy level of the dithiolene-based π-orbital in each of the complexes, which was controlled by changing R in FcS4dt(R)2 (R = Me for FcS4dt(Me)2; 2R = Pt((t)Bu2bpy) for FcS4dt[Pt((t)Bu2bpy)]). We succeeded in analyzing the crystal structure of [FcS4dt[Pt((t)Bu2bpy)]](F4TCNQ)·C6H14·CH2Cl2 (where F4TCNQ indicates 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane), which provided a rare example of the crystal structure of a [Pt(diimine)(dithiolate)](•+) ion-based complex. A comparison of the bond lengths in FcS4dt[Pt((t)Bu2bpy)] and [FcS4dt[Pt((t)Bu2bpy)]](•+) suggested that the latter complex displayed a conjugated dithiolene-based π-radical character. These considerations agreed well with the electronic structures calculated using density functional theory (DFT) and time-dependent(TD)-DFT methods. Significant electronic communication between the ferrocene and dithiolene moieties was detected for both [FcS4dt(Me)2](•+) and [FcS4dt[Pt((t)Bu2bpy)]](•+) in the appearance of an intramolecular charge transfer band, which was hardly observed for previously reported ferrocene-dithiolene hybrid molecules. The charge transfer direction was reversed between the two cations. The electron coupling parameter HAB and the potential energy curves of the oxidized complexes were estimated based on the classical two-state Marcus-Hush theory. These results suggest that FcS4dt-based metalladithiolenes can exhibit controllable electronic structures expressed as double-minimum potential energy curves.

The dithiolene ligand and tetrathiafulvalene precursor molecules 4,5-bis(bromomethyl)-1,3-dithiol-2-one and 4,5-bis[(dihydroxyphosphoryl)methyl]-1,3-dithiol-2-one

The crystal structures of 4,5-bis(bromomethyl)-1,3-dithiol-2-one, C(5)H(4)Br(2)OS(2), (I), and 4,5-bis[(dihydroxyphosphoryl)methyl]-1,3-dithiol-2-one, C(5)H(8)O(7)P(2)S(2), (II), occur with similar unit cells in the same monoclinic space group. Both molecules reside on a twofold symmetry axis coincident with the C=O bond, so that the substituents in the 4- and 5-positions project above and below the plane of the 1,3-dithiol-2-one ring. In both structures, the molecules align themselves in a head-to-tail fashion along the b axis, and these rows of molecules then stack, with alternating directionality, along the c axis. For (II), an extensive network of intermolecular hydrogen bonds occurs between molecules within the same stack and between adjacent stacks. Each -CH(2)P(O)(OH)(2) group participates in four hydrogen bonds, twice as donor and twice as acceptor.

Synthesis and redox behavior of new ferrocene-pi-extended-dithiafulvalenes: an approach for anticipated organic conductors

A number of new ferrocene-π-extended-dithiafulvalenes were successfully synthesized as new electron donor compounds. The chemical structures and electrochemical behaviors of these compounds were investigated using several spectroscopic methods. The synthesis of these compounds was achieved using the modified Wittig–Horner cross-coupling reaction using n-BuLi/THF at temperature varies from −78 °C to 0 °C. These new classes of bis(1,3-dithiafulvalene)ferrocenes have the 1,3-dithiole ring system separated by ferrocene as conjugated spacer. The ferrocene-dithiafulvalenes derivatives 9 and 12 were prepared as side products during the synthesis of the targeted compounds as bis(1,3-dithiafulvalene)ferrocenes 8, 10 and 11 in variable yields. The redox properties of the compounds have been investigated by cyclic voltammetry at ambient temperature using tetra-n-butylammonium perchlorate (TBAP) as the supporting electrolyte compared to ferrocene and the derivative 9. In CH₂Cl₂ on a Pt working electrode and at ambient temperature, two oxidation waves associated with two reduction waves at scan rates 100 mV s⁻¹ were observed for 9 and 12. In contrast the anodic peak potential of bis(1,3-dithiafulvalene)ferrocenes 8, 10 and 11 exhibited two and three oxidation waves associated with two reduction waves.