Tetrathiafulvalene structure

Variations on the theme of the tetrathiafulvalene structure have been investigated. Thus, the violene radical 156 has been characterized polaro-graphically and by electronic absorption spectra s 157, the phenylog of 154, has been reported the p-phenylenebis(tetrathiafulvalene) 158 gives an ESR spectrum upon oxidation which implies three equivalently coupling protons i.e., it behaves as a monosubstituted 153. ° There have been various attempts to incorporate the tetrathiafulvalene structure into polymeric materials, but with limited success in producing conducting polymers. i- ... 

Dithiolium ions, synthetic applications of 83SR(3)I 81YGK192. Organic superconductors based on tetrathiafulvalene, structure and design ... 

Tetrathiafulvalenes.—Preparations of ever more elaborate compounds of this class have been announced. Coupling of the dithiolethiones (293 n = 2 or 3) by means of triethyl phosphite affords the tetracyclic derivatives (294) °° mixtures of the dithioleselones (295) and (296) give good yields of the crossed product (297) in this reaction.The tetraselenafulvalene (299) is obtained by photolysis of 3,4-diphenyl-l,3-diselenole-2-thione (298). Even cyclophanes containing the tetrathiafulvalene structure have been reported thus compound (300), on sequential treatment with methyl iodide, sodium borohydride, and fluoroboric acid-acetic anhydride, affords a mixture of the tetrathiafulvalenophanes (301) and (302), ° and the paracyclophanes (304) and (305) result from the para-substituted benzene (303). 

The (EDT-TTF-I)2Br salt described above [36] and the 1 1 (TTFI4)I salt reported by Gompper [51] were the only structurally characterized salts with simple halide anions until Imakubo recently described an extensive series of Cl" and Br" salts from several ortho-diiodo tetrathiafulvalene, tetraselena-fulvalene and dithiadiselenafulvalene derivatives (Scheme 8) [62], The X-ray crystal structure analysis of the nine salts described there show a variety of halogen bonded motifs, demonstrating the adaptability of the supramolecu-lar interactions to other structural requirements imposed by the nature of the heteroatoms (O, S, Se) in the TTF frame. Indeed, in (EDT-TTF-l2)2X-(H20)2 (X = Cl, Br), a bimolecular motif (Fig. 6) associates two partially oxidized EDT-TTF-I2 molecules with one Br" anion and one water molecule. 

The silver(I) complexes with the tetrakis(methylthio)tetrathiafulvalene ligand have been reported, the nitrate salt presents a 3D structure with an unprecedented 4.16-net porous inorganic layer of silver nitrate,1160 the triflate salt presents a two interwoven polymeric chain structure.1161 The latter behaves as a semiconductor when doped with iodine. With a similar ligand, 2,5-bis-(5,5,-bis(methylthio)-l,3,-dithiol-2 -ylidene)-l,3,4,6-tetrathiapentalene, a 3D supramolecular network is constructed via coordination bonds and S"-S contacts. The iodine-doped compound is highly conductive.1162 (Methylthio)methyl-substituted calix[4]arenes have been used as silver-selective chemically modified field effect transistors and as potential extractants for Ag1.1163,1164... 

In recent years, the amount of research time devoted to materials chemistry has risen almost exponentially and sulfur-based radicals, such as the charge-transfer salts based upon TTF (tetrathiafulvalene), have played an important role in these developments. These TTF derivatives will not be discussed here but are dealt with elsewhere in this book. Instead we focus on recent developments in the area of group 15/16 free radicals. Up until the latter end of the last century, these radicals posed fundamental questions regarding the structure and bonding in main group chemistry. Now, in many cases, their thermodynamic and kinetic stability allows them to be used in the construction of molecular magnets and conductors. In this overview we will focus on the synthesis and characterisation of these radicals with a particular emphasis on their physical properties. 

The l,l -diferrocenyl-VT electron donor molecule is structurally similar to diferrocenyltetrathiafulvalene but with the TTF moiety replaced by bis(vinylene-dithio)tetrathiafulvalene (VT) [76]. It has currently not been possible to separate the cis- and trans-isomers. The 1 1 polyiodide complex of l,l -diferrocenyl-VT was obtained through reaction with iodine. EPR and Mossbauer spectra indicate that in this charge transfer salt the VT moiety is oxidized while the ferrocene... 

The redox reaction shown in Scheme 7.60 results in the formation of an amide a-radical and tetrathiafulvalene cation-radical. These initially formed a-radical and cation-radical combine to give salts of the S-arylated tetrathiafulvalene (a minor product) and C-alkylated tetrathiafulvalene (the main product). The latter demonstrates an unprecedented carbon-carbon bond formation with the cation-radical of tetrathiafulvalene the structure depicted was confirmed by single crystal x-ray analysis (Begley et al. 1994). 

Fe(C204)3] anions with associated water and PhCN. The tetrathiafulvalene derivatives (ttf)7[Fe(C204)3]2 4H20 and (ttf)5[Fe(C204)3] 2C6H5Me 2H20 are semiconductors with stacked structures. 

An unusual six-electron cycloaddition could be observed in the reaction of CgQpjg with tetrathiafulvalene (TTF) [70], TTF is not added to one of the free double bonds but replaces two of the fluorine atoms in a way that leaves the CgQpjg moiety, whose structure is described above (Figure 9.1). Under loss of F2 the product Cjq Fi6(TTF) is formed (Figure 9.7). 

Namely, when electron-transfer adsorbates such as the electron-acceptor tetra-cyanoethylene (TCNE) and electron-donor tetrathiafulvalene (TTF) molecules interact with the inorganic framework, the energy gap of the mesoporous NU-Ge-1 (1.87 eV) is red-shifted to 1.71 and 1.64 eV, respectively. Indeed, this change in electronic structure is reversible and the optical adsorption onsets going to 1.83 eV upon formation of the inactive TTF-TCNE complex inside the pores. Incorporation of molecules without electron-acceptor or electron-donor properties such as anthracene did not affect the electronic structure of NU-Ge-1. 

Emge TJ, Leung PCW, Beno MA, Schultz AJ, Wang HH, Sowa LM, Williams JM (1984) Neutron and X-ray diffraction evidence for a structural phase transition in the sulfur-based ambient-pressure organic superconductor bis(ethylenedithio)tetrathiafulvalene triiodide. Phys Rev B30 6780-6782... 

CV investigations of 6-mercaptopurine and 8-mercaptoquinoline SAMs on pc-Au electrodes have been presented by Madueno et al. [186] and He etal. [187], respectively. Several model electrode reactions involving various redox probes were studied using such modified electrodes. Baunach and Kolb etal. [188] have deposited copper on disordered benzyl mercaptan film on Au(lll) surfaces. They have also studied the behavior of benzyl mercaptan SAM on Au(lll) in H2SO4 solution using CV and STM. Structural and electrical properties of SAMs based on tetrathiafulvalene derivatives on Au(lll) were investigated. These mono-layers were disordered, or at least loosely... 

The prospective applications ofmolecular assemblies seem so wide that their limits are difficult to set. The sizes of electronic devices in the computer industry are close to their lower limits. One simply cannot fit many more electronic elements into a cell since the walls between the elements in the cell would become too thin to insulate them effectively. Thus further miniaturization of today s devices will soon be virtually impossible. Therefore, another approach from bottom up was proposed. It consists in the creation of electronic devices of the size of a single molecule or of a well-defined molecular aggregate. This is an enormous technological task and only the first steps in this direction have been taken. In the future, organic compounds and supramolecular complexes will serve as conductors, as well as semi- and superconductors, since they can be easily obtained with sufficient, controllable purity and their properties can be fine tuned by minor adjustments of their structures. For instance, the charge-transfer complex of tetrathiafulvalene 21 with tetramethylquinodimethane 22 exhibits room- temperature conductivity [30] close to that of metals. Therefore it could be called an organic metal. Several systems which could serve as molecular devices have been proposed. One example of such a system which can also act as a sensor consists of a basic solution of phenolophthalein dye 10b with P-cyciodextrin 11. The purple solution of the dye not only loses its colour upon the complexation but the colour comes back when the solution is heated [31]. 

Figure 11.10 (a) Chemical structures for MMPC 8, cyclophane 3, and tetrathiafulvalene 4. 

Single-Stack Donor. Ion-radical salts can also be formed from electron donors such as tetrathiafulvalene (TTF) or TMPD (AJ,AJ,AJ AJ-tetramethyl-/>-phenylene diamine) with inorganic acceptors such as halogens. The resulting structure of compounds such as TTF(A)... 

The crystal structure of pentathiepino [6,7- indole has been determined <1994TL5279>. X-Ray crystal structure analysis revealed that 4,5-ethylenedithio-4,5-pentathiotetrathiofulvalene <1999AM758> moiety has a bent structure resembling the molecular structure of neutral bis(ethylenedithio)tetrathiafulvalene and that the pentathio group adopts a chair-formed conformation. The intradimer interplane distance is 3.35 A, which is much shorter than the interdimer one (4.45 A). In a molecule, there are many intermolecular S-S contacts shorter than the sum of the van der Waals radii (3.7 A), and a two-dimensional network of sulfur atoms was developed between the pentathio groups and tetrathiafulvalene moieties. Furthermore, chlorobenzene molecules are beside the anion and occupy the void space as the interstitial solvent. They are also located on the mirror plane and are disordered at two positions with inversion symmetry because of the cavity structure of the void space. 

---