Thiolated pi-extended tetrathiafulvalenes: versatile multifunctional pi-systems

Derivatives of 9,10-bis(1,3-dithiol-2-ylidene)-9,10-dihydroanthracene (ex-TTF) have been synthesized by a new synthetic methodology, viz., direct phosphite-mediated cross-couplings of anthraquinone with 1,3-dithiole-2-thione derivatives. These ex-TTFs bear one, two, or four cyanoethyl-protected thiol groups on the dithiole rings. Deprotection (NaOMe, MeOH, DMF, 20 degrees C) and trapping of the transient thiolates with electrophiles have afforded the new ex-TTF trimer 19, dimeric cyclophanes 22 and 25, the tetrakis(hydroxyethylthio) derivative 23, and the strained cyclophane 24. Solution redox properties have been studied by cyclic voltammetry. For compounds 19, 22, and 25 each ex-TTF unit behaves as an independent 2-electron redox system giving rise to a single, quasi-reversible 6-, 4-, and 4-electron wave, respectively. The Eox value for 24 (0 --> 2+ wave) is positively shifted by 290 mV compared to that of its precursor 15 due to the short bridge in 24 obstructing the conformational change which accompanies oxidation. X-ray crystal structures of 23.2.5MeOH, 23.1.5MeCN, 24.CH2Cl2, and 24.1.5CH2Cl2 show the saddle-shape folding (typical of ex-TTF derivatives), which in 24 is enhanced by the pentamethylene chain bridging the dithiole units. Both solvates of 23 show an unprecedented crystal packing motif due to hydrogen bonding.     

Aza-analogues of extended tetrathiafulvalenes

The phosphoramidate-like reaction of 1,3-dithiole derived N-(diethoxyphosphinyl)hydrazones with formyl derivatives of 1,3-dithiole affords the longest aza-analogues of extended tetrathiafulvalenes with a polyenic spacer reported to date. Their structural and electrochemical properties are discussed.     

硫原子桥联芳基取代/稠合四硫富瓦烯

近年来,四硫富瓦烯(Tetrathiafulvalene,TTF)衍生物的设计合成、超分子组装、组装材料的物理性能研究及其在有机电子器件中的应用引起了人们广泛的研究兴趣。在本文中,我们简略综述硫原子桥联芳基取代/稠合四硫富瓦烯衍生物(Ar-S-TTF)的最新研究进展,包括其高效合成、电化学及光学性能研究、分子的结构特征/空间堆积方式,以及此类分子与球形原子簇(富勒烯、杂多酸)之间的超分子组装及组装材料的性能。     

Chiral, flexible binaphthol-substituted tetrathiafulvalenes

Novel chiral tetrathiafulvalene derivatives incorporating one or two binapthol moieties are described where two flexible (Ar-O)-CH₂-CH₂-S-(TTF) links generate a large 14-membered ring on one or both sides of the TTF core. The symmetric donor molecule with two chiral binaphthol moieties has been prepared as enantiopure (RR) or (SS) isomer, as well as diastereomeric mixture containing the (RR), (SS), and meso (RS)(SR) forms. Other unsymmetrically substituted derivatives bearing one single chiral binaphthol substituent on one side were also prepared in their enantiopure (R) and (S) forms and as racemic mixture. X-ray crystal structure determinations of different donor molecules show that the TTF tend to associate into face-to-face dyads with a strong folding of the dithiole rings along the S?S hinge while the binaphthol moieties adopt a cisoid conformation with a dihedral angle between naphthyl rings in the range 80-85°. The racemic EDT/TTF derivative allowed for the isolation of two crystalline charge-transfer compounds with the electron acceptors TCNQ and TCNQF₄. The donor and acceptor molecules are organized into homo-dyads in the TCNQ neutral complex, insulating and diamagnetic. On the other hand, a full charge transfer occurs in the TCNQF₄ salt, with weakly interacting chiral TTF cation and TCNQF₄ anion radicals.     

Incorporation of fused tetrathiafulvalenes (TTFs) into polythiophene architectures: varying the electroactive dominance of the TTF species in hybrid systems

A novel polythienylenevinylene (PTV) and two new polythiophenes (PTs), featuring fused tetrathiafulvalene (TTF) units, have been prepared and characterized by ultraviolet-visible (UV-vis) and electron paramagnetic resonance (EPR) spectroelectrochemistry. All polymers undergo two sequential, reversible oxidation processes in solution. Structures in which the TTF species is directly linked to the polymer backbone (2 and 4) display redox behavior which is dictated by the fulvalene system. Once the TTF is spatially removed from the polymer chain by a nonconjugated link (polymer 3), the electroactivity of both TTF and polythiophene moieties can be detected. Computational studies confirm the delocalization of charge over both electroactive centers (TTF and PT) and the existence of a triplet dication intermediate. PTV 4 has a low band gap (1.44 eV), is soluble in common organic solvents, and is stable under ambient conditions. Organic solar cells of polymer 4:[6,6]-phenyl-C(61) butyric acid methyl ester (PCBM) have been fabricated. Under illumination, a photovoltaic effect is observed with a power conversion efficiency of 0.13% under AM1.5 solar simulated light. The onset of photocurrent at 850 nm is consistent with the onset of the pi-pi absorption band of the polymer. Remarkably, UV-vis spectroelectrochemistry of polymer 4 reveals that the conjugated polymer chain remains unchanged during the oxidation of the polymer.     

Synthesis and reactivity of silylated tetrathiafulvalenes

Novel organosilylated tetrathiafulvalenes (TTFs) possessing Si-H or Si-Si bonds have been synthesised. The crystal structures of several derivatives have been determined by X-ray diffraction, including that of dimeric (Si(2)Me(4))(TTF)(2) () incorporating a diatomic SiMe(2)-SiMe(2) linker. Cyclic voltammetry measurements in all cases show two oxidation waves. DFT calculations were performed to rationalize the absence of an electronic communication between the two TTF moieties of through the disilanyl spacer. The reactivity of the Si-H bond has been exploited to prepare the dinuclear complex [{Ru(CO)(4)}(2){mu-(Me(2)Si)(4)TTF}] (), starting from Ru(3)(CO)(12) and TTF(SiMe(2)H)(4) (). Treatment of with 2 equiv. of PPh(3) or dppm results in selective substitution of a CO ligand trans to a SiMe(2) group to afford mer-[{Ru(PPh(3))(CO)(3)}(2){mu-(Me(2)Si)(4)TTF}] () and mer-[{Ru(CO)(3)}(2)(eta(1)-dppm){mu-(Me(2)Si)(4)TTF}] (). Attempts to transform the Si-H bonds of some TTF(SiMe(2)H)(n) (n = 1, 2) into Si-O functions using stoichiometric amounts of water in the presence of tris(dibenzylideneacetone)dipalladium(0) were unsuccessful. Quantitative cleavage of the C(TTF)-Si bond was observed instead of formation of TTF-based-siloxanes. Essays of catalytic bis-silylation of phenylacetylene with and TTF(SiMe(2)-SiMe(3)) () in the presence of Pd(OAc)(2)/1,1,3,3-tetramethylbutylisocyanide failed. Again, cleavage of the C(TTF)-Si bond was noticed.     

Chemistry of geminal-dithiolates derived from cyano-substituted tetrathiafulvalenes

Tetracyanotetrathiafulvalene reacts with two equivalents of thiol salts (RS^?) to give 1,2-dicyano-1,2-di RS ethene and a geminal dithiolate intermediate which reacts with a variety of reagents to provide novel tetrathioethene derivatives, such as reaction with 3-chloro-2-butanone and acid to give dimethyldicyanotetrathiafulvalene.     

1,4-Dihydro-1,4-diphosphinine fused with two tetrathiafulvalenes

Electrochemical and theoretical investigations demonstrate through-bond interactions between two TTF moieties fused to a 1,4-dihydro-1,4-diphosphinine, for which the single crystal X-ray structure of the cis isomer is described together with that of a mixed-valent, charge-localized, radical cation salt with Mo6O19(2-), obtained upon electrocrystallization of the same cis isomer.     

Novel extended tetrathiafulvalenes based on acetylenic spacers: synthesis and electronic properties

A selection of mono- and diacetylenic dithiafulvalenes was synthesized and employed for the construction of extended tetrathiafulvalenes (TTFs) with hexa-2,4-diyne-1,6-diylidene or deca-2,4,6,8-tetrayne-1,10-diylidene spacers between the two 1,3-dithiole rings. By stepwise acetylenic scaffolding using (E)-1,2-diethynylethene (DEE) building blocks, an extended TTF containing a total of 18 C(sp) and C(sp(2)) atoms in the spacer was prepared. The versatility of the acetylenic dithiafulvene modules was also established by the efficient synthesis of a thiophene-spaced TTF, employing a palladium-catalyzed cross-coupling reaction. The developed synthetic protocols allow functionalization of the extended TTFs in three general ways: with 1) peripheral substituents on the fulvalene cores, 2) alkynyl moieties laterally appended to the spacer, and 3) cobalt clusters involving acetylenic moieties. Strong chromophoric properties of the extended TTFs were revealed by linear and nonlinear optical spectroscopies. Extensive electrochemical studies and calculations on these compounds are also reported, as well as X-ray crystallographic analyses.     

Oligomeric tetrathiafulvalenes: a new route toward conjugated TTF dimers and trimers

The synthesis of bis-TTF 1 and tris-TTF 2, linked by an ethenyl spacer, is described using new useful Wittig-type reagents with the introduction of phosphonate functionality on 1,3-dithiole and TTF frameworks. Electrochemical and spectroscopic studies show intramolecular electronic interactions between conjugated TTF units.     

Mass spectra of tetraselenafulvalenes,diselenadithiafulvalenes and tetrathiafulvalenes

The mass spectra of 13 heterofulvalenes are reported. The spectra show great similarities within the selenium and within the sulphur series. The main difference between the selenium and the sulphur compounds results from the more facile loss of selenium compared with sulphur, and from the first fragmentation of the molecular ion, as the selenium fulvalenes lose an alkyne molecule, whereas the sulphur fulvalenes first lose an (S?R) radical. An important feature of the spectra of the simple heterofulvalenes is the formation of a rearrangement ion by migration of a heteroatom. The mechanism was elucidated by ¹³C labelling and is discussed in detail.     

Dimeric and trimeric tetrathiafulvalenes with strong intramolecular interactions in the oxidized states

New dimeric and trimeric TTF derivatives with methylenedithio spacers (1a,b, 2a, and 2b) have been synthesized. X-ray structure analysis revealed that TTF units of the dimer 1b adopted distorted face-to-face overlapping arrangement both in intra- and intermolecular stacking. Cyclic voltammetric study indicated that trimeric 2a was in favor of taking di- and tetracationic states, while the dimeric 1a was in favor of taking a monocation. The absorption spectroscopic study suggested an existence of the strong face-to-face interaction particularly in di-, tri-, and tetracationic state of the trimeric TTF derivatives.     

Synthesis of the precursors of bis(trichloro-1,4-benzoquinonyl)tetrathiafulvalenes

In reaction with potassium butylxanthate and sodium tert-butyltrithionate, 2,5-dihydroxy-3,4,6,7-tetrachloro-2,3-dihydrobenzo[b]furan forms the products from nucleophilic substitution of a chlorine atom, i.e., O-butyl S-(2,5-dihydroxy-4,6,7-trichloro-2,3-dihydrobenzo[b]furan-3-yl) xanthate and S-tert-butyl S-(2,5-dihydroxy-4,6,7-trichloro-2,3-dihydrobenzo[b]furan-3-yl) trithiocarbonate respectively. Recyclization of the xanthate in concentrated sulfuric acid gave 4-(2,5-dihydroxy-3,4,6-trichlorophenyl)-1,3-dithiol-2-one, which was oxidized by iron trichloride to the corresponding benzoquinone. Cyclization of the trithiocarbonate in the presence of trifluoroacetic and p-toluenesulfonic acid led to 7-hydroxy-5,6,8-trichloro-3a,8b-dithiolo[4,5-b]benzo[d]furan-2-thione.Dedicated to Prof. A. Katritzky in honor of his seventieth birthday.Riga Technical University, Riga LV-1048, Latvia. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1055–1060, August, 1998.     

Synthesis and characterization of alkene-extended tetrathiafulvalenes with lateral alkyne appendages

Tetrathiafulvalene (TTF) derivatives containing a diethynyl-substituted alkene spacer were synthesized and investigated for their electronic and structural properties. Co-planarity of the central diethynylethene unit and the two dithiole rings were confirmed by X-ray crystallographic analysis.     

双（亚烷二硫基)四硫富瓦烯衍生物的合成及其电化学性质

以四(氰乙硫基)四硫富瓦烯为原料经醇钠消去氰乙基生成四硫富瓦烯四硫盐， 再与二元卤代烷烃化反应，除了得到三种文献报道的双(亚烷二硫基)四硫富瓦烯衍 生物外，还得到三种新的“四桥”双—四硫富瓦烯衍生物，为“桥式”双—四硫富 瓦烯衍生物的合成提出了一种新的方法．并研究了它们的循环伏安图、电化学性质 和紫外—可见光光谱．     

Interfacing nanocarbons with organic and inorganic semiconductors: from nanocrystals/quantum dots to extended tetrathiafulvalenes

There is no doubt that the outstanding optical and electronic properties that low-dimensional carbon-based nanomaterials exhibit call for their implementation into optoelectronic devices. However, to harvest the enormous potential of these nanocarbons it is essential to probe them in multifunctional electron donor-acceptor systems, placing particular attention on the interactions between electron donors/electron acceptors and nanocarbons. This feature article outlines challenges and recent breakthroughs in the area of interfacing organic and inorganic semiconductors with low-dimensional nanocarbons that range from fullerenes (0D) and carbon nanotubes (1D) to graphene (2D). In the context of organic semiconductors, we focus on aromatic macrocycles and extended tetrathiafulvalenes, and CdTe nanocrystals/quantum dots represent the inorganic semiconductors. Particular emphasis is placed on designing and probing solar energy conversion nanohybrids.     

Synthesis of tetrahydroxy-π-extended tetrathiafulvalenes as new supramolecular redox building blocks

A novel p-quinonoid π-extended tetrathiafulvalene (exTTF) endowed with four hydroxy groups with different reactivity (phenol and alcohol) has been synthesized as a supramolecular redox building block. The redox properties, studied by cyclic voltammetry, reveal a strong donor ability and, despite the different substitution pattern on the 1,3-dithiole rings, only one oxidation wave involving two electrons to form the dication species.     

Synthesis and properties of thiophene-functionalized π-extended tetrathiafulvalenes

Two molecular ensembles composed of an array of thiophene–extended tetrathiafulvalene–thiophene were synthesized using Stille coupling and Horner–Wittig reaction as the key steps. Electrochemical redox and electronic absorption properties were investigated by voltammetric and UV–vis spectroscopic analyses.