Charge-transfer complex of TTF

Morita Y, Maki S, Ohmoto M, Kitagawa H, Okubo T, Mitani T, Nakasuji K (2002) Hydrogen-bonded charge-transfer complexes of TTF containing a uracil moiety crystal structures and electronic properties of the hydrogen cyananilate and TCNQ complexes. Org Lett 4 2185-2188... 

The discovery of the unusually high solid-state electrical conductivity of the charge-transfer complex of TTF with TCNQ has prompted extensive investigations of 1,3-dithiolium salts, an important class of intermediates for the synthesis of tetrathiafulvalene derivatives. 

The charge-transfer complexes of TTF with various acceptors exhibit interesting electrical conductivities (listed in Ref. 268 p. 512). For example, the room-temperature electrical conductivity of (TTF)+(TCNQ) is 652 cm and increases considerably with decreasing temperature with a... 

Murata, T., Morita, Y, Yakiyama, Y, Fukui, K., Yamochi, H., Saito, G., and Nakasuji, K. 2007. Hydrogen-bond interaction in organic conductors Redox activation, molecular recognition, structural regulation, and proton transfer in donor-acceptor charge-transfer complexes of TTF-imidazole. /. Am. Chem. Soc. 129 10837-10846. 

The LB films of charge-transfer complexes of C TET-TTF, long-chain derivatives of BEDT-TTF, with F4TCNQ were fabricated to try to obtain high conductivities [67-69]. The iodine doping of the LB film yields a conductivity on the order of 10 2 S/cm, which is considered to be due to reduction of the donor. The LB films of a series of 3,4,5-(alkylthio)-l,2-dithiolium and TCNQ were also fabricated [70,71]. The binary mixed LB films were investigated for amphiphilic donors, TTF and BEDT-TTF derivatives, amphiphilic acceptors, TCNQ, and anthraquinodimethane derivatives [72]. There is an LB film based on a charge-transfer complex with... 

Another electron-accepting quinoid selenophene is 35, with a unique [3]radialene Iramework developed by Takahashi and Tarutani [80]. It has strong electron-accepting ability comparable to that of TCNQ and forms charge-transfer complexes with TTF and tetrathiotetracene, which have extraordinarily high conductivities of 420 and 450 Scm", respectively. 

The crystal structures of the charge-transfer complexes of two isomeric thiophene-fiised TCNQs, 4,8-bis(dicy anomethy lene)-4,8 -dihy drobenzo [ 1,2 -fc 4,5 -6 ] -dithiophene (45) and the [l,2-i> 4,5-c ]isomer (47) with the strong donor TTF have been determined by X-ray analysis with different results. Thus while the 45-TTF complex forms pairs of TTF and TCNQ derivatives in... 

In addition to the aromatic amines, many kinds of organic compounds are known to show sufficient donor abilities. For example, tetrathiafulvalene (TTF) or bis(ethylene-dithio)tetrathiafulvalene (BEDT-TTF) is a donor which shows metallic conduction when it forms a charge-transfer complex with appropriate acceptors [49]. Cgg is one of the acceptors which forms a charge-transfer complex with TTF [50]. In benzonitrile solution which contains Cgg and TTF,... 

The structures of the black crystalline benzene solvate C6o-4C6H6, the black charge-transfer complex with bis(ethylenedithio)tetrathiafulvene, [C6o(BEDT-TTF)2], and the black ferrocene adduct [C6o Fe(Cp)2)2] (Fig. 8.7b) ) have also been solved and all feature the packing of Cso clusters. 

The synthesis of the bis-l,3-dithiolium radical cation (TTF+) in 1970 [1] enabled dramatic growth in the field of molecular conductors in the decades thereafter. TTF and several of its homologues are depicted in Scheme 1. The field of low dimensional molecular metals was further motivated by the discovery of the TTF-TCNQ charge-transfer complex in 1973 [2, 3]. Seven years later, superconductivity was induced in the cation-radical salt, (TMTSF)2PF6, upon application of 12 kbar pressure [4]. Shortly thereafter, superconductivity below 1.4 K was observed at ambient pressure in the perchlorate analog [5]. 

Over the past decade a number of new covalently bonded TTF/ferrocene adducts have been reported [77, 78]. The crystal structure of the l,l -bis(l,3-dithiole-2-ylidine)-substituted ferrocene derivative has been published [77]. In this complex, ferrocene has essentially been incorporated as a molecular spacer between the two l,3-dithole-2-ylidene rings forming a stretched TTF molecule. This adduct, and its methyl-substituted derivative, have been combined with TCNQ to form charge-transfer complexes with room temperature powder conductivities of 0.2 S cm-1. Similar diferrocenyl complexes have been prepared with bis (dithiolene) metal complexes [79, 80]. 

Double pump experiments on an organic charge transfer complex TTF-CA by Iwai and coworkers demonstrated a new class of coherent control on a strongly correlated electron-lattice system [44]. While the amplitude of the coherent oscillation increased linearly with pump fluence for single pump experiments, the amplitude in the double pump experiments with a fixed pulse interval At = T exhibited a strongly super-linear fluence dependence (Fig. 3.16). The striking difference between the single- and double-pulse results indicated a cooperative nature of the photo-induced neutral-ionic transition. 

Chemical oxidation of the TTF groups in compounds 34 and 35 has been achieved by reaction with an excess of iodine in dichloromethane solution, leading to new low-energy absorptions in the UV/visible spectra which are diagnostic of TTF cation radicals the broad absorption at = 830 nm for the iodide salt of 35 suggests the formation of aggregated TTF species. A charge transfer complex formed by 35 and tetracyano-p-quinodimethane (TCNQ) has been isolated as an insoluble black powder. The stoichiometry is (35), (TCNQ)3 (i.e. 8 TTF units 3... 

Bulk crystalline radical ion salts and electron donor-electron acceptor charge transfer complexes have been shown to have room temperature d.c. conductivities up to 500 Scm-1 [457, 720, 721]. Tetrathiafiilvalene (TTF), tetraselenoful-valene (TST), and bis-ethyldithiotetrathiafulvalene (BEDT-TTF) have been the most commonly used electron donors, while tetracyano p-quinodimethane (TCNQ) and nickel 4,5-dimercapto-l,3-dithiol-2-thione Ni(dmit)2 have been the most commonly utilized electron acceptors (see Table 8). Metallic behavior in charge transfer complexes is believed to originate in the facile electron movements in the partially filled bands and in the interaction of the electrons with the vibrations of the atomic lattice (phonons). Lowering the temperature causes fewer lattice vibrations and increases the intermolecular orbital overlap and, hence, the conductivity. The good correlation obtained between the position of the maximum of the charge transfer absorption band (proportional to... 

In addition to ferrocene, the oxidative redox couple that has received the most attention in supramolecular chemistry is tetrathiofulvalene (TTF), 35. This compound undergoes two reversible one-electron oxidations, first to a radical cation and then to a dication (Eq. 1.21). TTF first came to prominence in the 1970s when it was discovered that the charge transfer complex between it and 7,7,8,8-tetracyanoquinonedimethane (TCNQ) shows metallic conductivity. As a result, a large variety of different TTF derivatives have been prepared and characterized. This rich synthetic chemistry, coupled with the electroactivity, has intrigued supramolecular chemists for some time, with the result that the TTF unit has been incorporated into a wide variety of... 

Figure 1 Relationship of donor and acceptor molecules in charge transfer complexes (a) mixed stacks of alternating donor and acceptor molecules in a normal charge transfer complex (b) segregated stacks of donor and acceptor molecules in (TTF)(TCNQ) and related materials...

A particular subgroup of these low-dimensional conductors are the charge transfer complexes between dithiolenes and organic donor species such as TTF and related compounds. Here, nonintegral charge transfer is often seen as the reason for high conductivity down to low temperatures. 

---