TTF Skeleton Research Articles

Cytosine-fused TTF: Conducting property of single-component betainic radical and self-assembling ability of hemi-deprotonated cytosine pair

A new tetrathiafulvalene (TTF) electron-donor molecule fused with 2-oxo-4-amino-pyrimido (cytosine) ring was synthesized. The electrochemical measurement revealed that the deprotonation on the pyrimido-ring greatly strengthened the electron-donating ability of the TTF skeleton. The neutral betainic radical in which the cytosine and TTF skeleton were the deprotonated anion and radical cation, respectively, exhibited a high conductivity of ∼10−3 S cm−1 as a single-component organic molecule. In the crystal structure of the salt composed of 1:1 composite of neutral and deprotonated anion formed a new self-assembling structure of cytosine, a hemi-deprotonated cytosine pair, through triple complementary hydrogen-bonds.

Synthesis, Structure and Physical Properties of (trans-TTF-py2)1.5(PF6)·EtOH: A Molecular Conductor with Weak CH∙∙∙N Hydrogen Bondings

The studies of crystal structures with hydrogen bonds have been actively pursued because of their moderate stabilization energy for constructing unique structures. In this study, we synthesized a molecular conductor based on 2,6-bis(4-pyridyl)-1,4,5,8-tetrathiafulvalene (trans-TTF-py2). Two pyridyl groups were introduced into the TTF skeleton toward the structural exploration in TTF-based molecular conductors involved by hydrogen bonds. In the obtained molecular conductor, (trans-TTF-py2)1.5(PF6)·EtOH, short contacts between the pyridyl group and the hydrogen atom of the TTF skeleton were observed, indicating that hydrogen bonding interactions were introduced in the crystal structure. Spectroscopic measurements and conductivity measurement revealed semiconducting behavior derived from π-stacked trans-TTF-py2 radical in the crystal structure. Finally, these results are discussed with the quantified hydrogen bonding stabilization energy, and the band calculation of the crystal obtained from density functional theory calculation.

Crystal structures and properties of radical salts of a new series of tetrathiafulvalene derivatives incorporating fused ethyleneoxymethylene and ethylenethiomethylene units

Tetrathiafulvalene (TTF) derivatives have been widely investigated as functional molecular materials with conducting properties. Radical salts of tetrathiafulvalene (TTF) derivatives incorporating fused ethyleneoxymethylene (EOM) and ethylenethiomethylene (ETM) units were prepared by electrochemical oxidation. Crystal structures of some salts were determined by X-ray structure analyses. The AuI2 salt of bis(ethyleneoxymethylene)-TTF (BEOM-TTF) (1) exhibits a metal-to-semiconductor (MS) transition at 295 K with a high room-temperature conductivity (σRT) of 25 S cm–1 as determined by a two-probe method. Bis(ethylenethiomethylene)-TTF (BETM-TTF) (2) salts with 1:1 stoichiometry are insulators. The Br salt of 4,5-ethyleneoxymethylene-4′,5′-ethylenedithio-TTF (EOMEDT-TTF) (3) exhibits a MS transition at 297 K with a high σRT of 11 S cm–1. 32X salts (X = ClO4–, PF6–) have columnar structures and form head-to-tail dimers with O⋯H short contacts of the EOM groups. The ReO4 salt of 4,5-ethyleneoxymethylene-4′,5′-methylenedithio-TTF (EOMMDT-TTF) (4) exhibits a MS transition at 297 K with σRT of 4.2 S cm–1 and a small activation energy of 0.023 eV below 297 K, and adopts κ-type packing. The salts of ethyleneoxymethylene-TTF (EOM-TTF) (5) and ethylenethiomethylene-TTF (ETM-TTF) (6) donors exhibit semiconductive behaviors. The salt of 53(ClO4)2 has three crystallographically independent molecules and adopts head-to-head stacking with S⋯S and O⋯H short contacts in the triad. By comparing the intramolecular bond lengths of the molecules and splitting of the Raman bands, it was found that the 53(ClO4)2 salt is in a charge order state. Incorporation of the EOM and ETM functional substituents on the TTF skeleton gives rise to many intermolecular interactions between donors in their salts.

動的水素結合を活用した新しい電子機能性有機結晶の開発

Molecular crystalline materials that comprise π-electron organic molecules exhibit various interesting physical properties and functionalities related to electrical conductivity and magnetic, dielectric, and optical properties. Their experimental and theoretical studies have extensively been performed by a wide range of researchers in the fields of organic chemistry, physical chemistry, solid-state physics, and so on. In particular, synthetic organic chemists have devoted continuous effort to the design and synthesis of new functional molecular crystals and component molecules, which led to numerous important discoveries in this interdisciplinary research field. Here we report the development of a new type of organic conductors based on catechol-fused tetrathiafulvalene (TTF) derivatives. Interestingly, dynamic properties of hydrogen bonds through the catechol moiety are coupled with π-electrons on the TTF skeleton, which allowed us to discover unprecedented phase transitions, physical properties, and functionalities. In this paper, the design, synthesis, structures, and properties of our new molecules and crystals are described from a molecular point of view.

Modulation of a Molecular π-Electron System in a Purely Organic Conductor that Shows Hydrogen-Bond-Dynamics-Based Switching of Conductivity and Magnetism.

New important aspects of the hydrogen-bond (H-bond)-dynamics-based switching of electrical conductivity and magnetism in an H-bonded, purely organic conductor crystal have been discovered by modulating its tetrathiafulvalene (TTF)-based molecular π-electron system by means of partial sulfur/selenium substitution. The prepared selenium analogue also showed a similar type of phase transition, induced by H-bonded deuterium transfer followed by electron transfer between the H-bonded TTF skeletons, and the resulting switching of the physical properties; however, subtle but critical differences due to sulfur/selenium substitution were detected in the electronic structure, phase transition nature, and switching function. A molecular-level discussion based on the crystal structures shows that this chemical modification of the TTF skeleton influences not only its own π-electronic structure and π-π interactions within the conducting layer, but also the H-bond dynamics between the TTF π skeletons in the neighboring layers, which enables modulation of the interplay between the H-bond and π electrons to cause such differences.

Syntheses and properties of a new series of tetrathiafulvalene derivatives incorporating fused ethyleneoxymethylene and ethylenethiomethylene units, and their charge–transfer complexes

Nine tetrathiafulvalene (TTF) derivatives incorporating fused ethyleneoxymethylene (EOM) and ethylenethiomethylene (ETM) units were newly synthesized by self-coupling or cross-coupling reactions. Unsymmetrical ETMEDT-TTF (4) was also synthesized by a Wittig-type reaction. Crystal structural analysis of these neutral donors revealed specific intermolecular interactions between donors, and many S⋯S, O⋯H, and S⋯H short contacts. Electrochemical properties of these donors were investigated by cyclic voltammetry under two different measurement conditions. Electronic spectra of neutral donors in chloroform and some cation radicals in methanol and on KBr pellets were measured and discussed. A distribution of the highest occupied molecular orbital (HOMO) around the EOM and ETM moieties of these donors was not found. The introduction of EOM and ETM groups to the TTF skeleton only slightly modulated the HOMO energy. Some charge–transfer (CT) complexes of these donors with tetracyanoquinodimethane (TCNQ) derivatives were prepared. A needle crystal of the CT complex of EOMMDT-TTF (5) with TCNQ was metallic down to 102K with a high σRT value of 169Scm−1. TTF derivatives incorporating fused EOM groups were more effective in conductivity than those incorporating fused ETM groups.

Theoretical study on charge carrier mobilities of tetrathiafulvalene derivatives

We calculated the hole and electron mobilities of tetrathiafulvalene (TTF) derivative crystals using first-principles calculations and the Marcus theory of electron transfer. The hole and electron reorganization energies were found to decrease with the extension of π-conjugated orbitals. The calculated hole mobilities of TTF, dibenzo-tetrathiafulvalene (DB-TTF), and dinaphtho-tetrathiafulvalene (DN-TTF) agree well with the experimental results. In addition, with the increase of the number of benzene rings attached to the TTF skeleton, the hole mobilities decrease and the electron mobilities increase. The calculated electron mobility of dianthro-tetrathiafulvalene (DA-TTF) based on a virtual crystal structure is much larger than the hole one due to the small electron reorganization energy and large electron coupling. This suggests that the charge transfer properties of the TTF derivatives can be modified when the number of aromatic rings on TTF skeleton increases.

Novel Type of Career Generated System: Magnetic Investigations of TTF-Based Self-Doped Hydrogen-Bonding Conductor

Magnetic investigations, including static magnetic susceptibility and high-field electron spin resonance (ESR) measurements, were carried out for an organic conductor, (TTFCOO)[(NH 4 +1 ) 1- x (NH 3 ) x ]. Anisotropic ESR parameters were determined for powder samples using a high-frequency W-band (93.9817 GHz) ESR spectrometer. The observed principal values of the g -tensor and quantum chemical calculation results indicate that the observed spin is distributed on quasi-hole-like TTF skeletons, and that the TTFCOO mainframe partially becomes a neutral radical. The temperature dependence of the spin susceptibility is well fitted with a Curie–Weiss term and an activation-type term, with the activation-type term dominant at high temperatures. The high absolute value of the spin susceptibility and the extremely small activation energy, Δ, indicate that a quasi-degenerate (metallic) state is stabilized in (TTFCOO)[(NH 4 +1 ) 1- x (NH 3 ) x ], although the weakly temperature-dependent ESR linewidth indicates a l...

Hybrid Organic/Inorganic Complexes Based on Electroactive Tetrathiafulvalene-Functionalized Diphosphanes Tethered to C3-Symmetrized Mo3Q4 (Q = S, Se) Clusters

A two-step procedure for the preparation of hybrid complexes based on electroactive tetrathiafulvalene (TTF)- functionalized o-P(2) diphosphanes (o-P(2) = 3,4-dimethyl-3,4-bis(diphenylphosphino)tetrathiafulvalene) and inorganic C(3)-symmetrized Mo(3)Q(4) (Q = S, Se) clusters, namely, [Mo(3)S(4)Cl(3)(o-P(2))(3)]PF(6) ([1]PF(6)) and [Mo(3)Se(4)Cl(3)(o-P(2))(3)]PF(6) ([2]PF(6)), is reported. Their molecular and electronic structures are also described on the basis of X-ray diffraction experiments and density functional theory (DFT) calculations aimed at understanding the interactions established between both the organic and the inorganic parts. Cyclic voltammograms of compounds [1]PF(6) and [2]PF(6) display reduction features associated to the Mo(3)Q(4) core and oxidation characteristics due to the TTF skeleton. The oxidation chemistry of [1]PF(6) and [2]PF(6) in solution is also investigated by means of in situ electrospray ionization (ESI) mass spectrometry, UV-vis, and, electron paramagnetic resonance (EPR) measurements. Upon addition of increasing amounts of NOPF(6) (less than 3 equiv), the sequential formation of 1(n+) (n = 1-4) species was observed whereas addition of a 3-fold excess of NOPF(6) allows to access the three-electron oxidized [Mo(3)S(4)Cl(3)(o-P(2))(3)](4+) (1(4+)) and [Mo(3)Se(4)Cl(3)(o-P(2))(3)](4+) (2(4+)) cations. These 1(4+) and 2(4+) cations represent still rare examples of complexes with oxidized TTF-ligands that are remarkably stable either toward diphosphane dissociation or phosphane oxidation. Polycrystalline samples of compound [1](PF(6))(4) were obtained by oxidation of compound [1]PF(6) using NOPF(6) which were analyzed by solid state absorption, UV-vis, and Raman spectroscopies.

Preparations and characterizations of new series of TTF ligands containing a nitrogen aromatic heterocycle

The detailed synthesis of a new series of conjugated TTF ligands with nitrogen-based aromatic heterocycle are presented. In all these molecules, trimethyl-TTF or TTF skeleton are bridged to the nitrogen aromatic ligand through a conjugated spacer such as ethenyl or phenylethenyl unit. Their electrochemical characterization as well as the crystal structure of one of these compounds is given.

Synthesis, crystal structure, and charge-transfer complexes of TTF derivatives having two imidazole hydrogen-bonding units

New hydrogen-bond functionalized tetrathiafulvalene (TTF) derivatives ( 1 and 2) having two imidazole moieties, which are attached to TTF at the 2- and 4-positions in the imidazole ring, respectively, were synthesized. Electrochemical measurements indicated that the introduction of imidazole moieties at 2- or 4-positions slightly reduced or enhanced the electron-donating ability of TTF. In the crystal structure of 1, N–H⋯N hydrogen-bonds of the imidazole ring formed a two-dimensional sheet, and further π-stacks on the TTF skeleton built up a one-dimensional column. Mixing 1 with electron-acceptors afforded fully ionic charge-transfer complexes having a 1:1 donor–acceptor ratio, while complex formation of 2 with tetracyanoquinodimethane and p-chloranil yielded partial charge-transfer complexes showing semiconducting behaviors (room temperature conductivities=10 −3–10 −2 S cm −1).

Supramolecular organic conductors based on diiodo-TTFs and spherical halide ion X−(X = Cl, Br)

Novel organic conductors based on four diiodotetrathiafulvalene derivatives, DIET (2-(4,5-diiodo-[1,3]dithiol-2-ylidene)-5,6-dihydro-[1,3]dithiolo[4,5-b][1,4]dithiine), DIETSe (2-(4,5-diiodo-[1,3]diselenol-2-ylidene)-5,6-dihydro-[1,3]diselenolo[4,5-b][1,4]dithiine), DIEDO (2-(4,5-diiodo-[1,3]dithiol-2-ylidene)-5,6-dihydro-[1,3]dithiolo[4,5-b][1,4]dioxine) and DIEDO-STF (2-(4,5-diiodo-[1,3]diselenol-2-ylidene)-5,6-dihydro-[1,3]dithiolo[4,5-b][1,4]dioxine) have been prepared using spherical halide ion X− (X = Cl, Br) as the counter anion. Crystal structure analyses have revealed that all halide salts contain supramolecular structures tailored by the strong I⋯X iodine bond and their molecular arrangement depends on the combination of the group 16 elements included in the donor molecule. The temperature dependence of the electrical resistivity of (DIET)2X(H2O)2 is metallic down to 4.2 K, and they have ideally two-dimensional Fermi surfaces within the donor layer. (DIETSe)2X(CH2Cl2) salts show small temperature dependence of the resistivity down to low temperatures and their “double column” structure is dominated by the Y-shaped architecture composed of the halide ion and the crystalline solvent. On the other hand, (DIEDO)2X and (DIEDO-STF)2X are semiconducting from room temperature. They have another type of “double column” structure, i.e. the adjacent donor molecules along the side-by-side direction are solid-crossing and two types of column are included in the donor layer. The packing motifs of the halide salts based on the oxygen-substituted donor molecules are the same but their electronic states are sensitive to changes in the chalcogen atoms on the inner TTF skeleton.

High-Performance Organic Field-Effect Transistors Based on π-Extended Tetrathiafulvalene Derivatives

Aromatic ring-condensed TTF derivatives exhibited excellent p-type FET performances in thin films. Introduction of fused benzene and pyrazine rings to the TTF skeleton was effective to enhance the intermolecular interactions and stability to oxygen. Ordered molecular alignment was confirmed by XRD studies. A pi-stacking structure was observed in the single crystal of diquinoxalinoTTF.

Covalent association of the redox-active TTF framework to N-ligands for the coordination of transition-metal cations

The synthesis as well as the solution characterization of electroactive assemblies associating the TTF core and N-ligands are presented. Two families of ligands L1 and L2 have been designed for the coordination of transition metals. Polyaza-macrocycles L1 and notably N 4 (cyclam) (L1a) or N 2 O 4 (Lie) macrocyclic units were grafted to the TTF framework under high pressure conditions. The introduction of the pyridyl moiety has been realized on the periphery of the TTF skeleton to give rise to the new electroactive ligand L2. Ligands L1 and L2 have been electrochemically characterized, including their ability to coordinate metal cations.

Hydrogen-bonded charge-transfer complexes of TTF containing a uracil moiety: crystal structures and electronic properties of the hydrogen cyananilate and TCNQ complexes.

[structure: see text] A novel TTF-based donor with a uracil moiety, TTF-(1-n-butyluracil-5-yl) (TnbU), was synthesized. Crystal structures of both TnbU and the charge-transfer complex of TnbU-hydrogen cyananilate possess complementary double hydrogen bonds through uracil moieties and pi-stacking dimer structures between TTF skeletons. Furthermore, the TnbU-TCNQ charge-transfer complex shows a high electrical conductivity underlying the partial charge-transfer accompanied by a hydrogen-bonding interaction, which was substantiated in terms of the measurements of the IR, electronic spectra, and conductivity.

Synthesis, structures and physical properties of the cation radical salts based on tempo radical containing electron donors

We have synthesized new electron donors in which one or two TEMPO radical parts connect to the TTF skeleton through a 1,3-dithiol-2-ylidene ring to prevent the steric hindrance of the bulky TEMPO radical for the purpose of the realization of metallic conductivity. Furthermore crystal structure and physical properties of the donors and the cation radical salt have been clarified.

Multi-property materials combining conductivity and second-order optical nonlinearity

We present several new materials made of acceptor units (TCNQ and [Ni(dmit) 2]) and stilbazolium-based chromophores for second-order optical nonlinearity. The subtil adjustement in the redox potentials necessary for: ( i) maintaining the material in a semi-conducting state, to offer a good range of transparency in a broad nearinfrared domain; ( ii) allowing electronic interaction, to promote a pathway towards efficient interplays between the properties is analyzed The possibility of combining both properties on the same entity with the TTF skeleton is also discussed.

Synthesis and properties of new organic donor containing organic radical part

Recently interplay between conductivity and magnetism has been focused in the research of new organic conductors. In this work, novel electron donor TEMPOET which is consisted of the extended TTF skeleton and stable TEMPO radical part was synthesized. The ESR spectra of TEMPOET indicated three absorption lines (g =2.0062, a N = 15.1 G) characteristic of the TEMPO radical. It is revealed that TEMPOET shows paramagnetic susceptibility corresponding to one spin per molecule and slightly antiferromagnetic interaction at low temperature region (θ = −1.00 K). The CV measurement revealed TEMPOET shows one pair of reversible redox waves (0.88 V vs. Ag/AgCl) and three pairs of irreversible ones (+0.56, +1.17, +1.77V).

Halogenated tetrathiafulvalenes (TTFs): preparation, X-ray structure and cyclic voltammetry of tetrachioro-, 2,3-dichloro-6,7-dimethyl- and 2,3-diiodo-6,7-dimethyl-TTF

Lithiation of tetrathiafulvalene (TTF) with butyllithium in tetrahydrofuran (THF) followed by quenching with hexachloroethane (HCE), 1,2-dibromotetrachloroethane (BCE) or 1,2-dibromotetrafluoroethane (BFE) affords improved yields of both tetrabromo-TTF (Br4TTF) and tetrachloro-TTF (Cl4TTF), compared to earlier reports. By a similar procedure, 2,3-dimethyl-TTF (2,3-Me2TTF) undergoes lithiation followed by chlorination with HCE, bromination with BCE or BFE and iodination with perfluorohexyl iodide (PFHI), affording 2,3-dichloro-6,7-dimethyl-TTF (Cl2Me2TTF), 2,3-dibromo-6,7-dimethyl-TTF (Br2Me2TTF) and 2,3-diiodo-6,7-dimethyl-TTF (I2Me2TTF), respectively. The single-crystal structures of Cl4TTF, Cl2Me2TTF and I2Me2TTF have been determined. Halogen substitution on the TTF skeleton leads to a variety of packing features in the crystal structures of the resulting compounds.

Calculation of positron states in the BEDT-TFF based organic superconductors

Positron states in the BEDT-TTF based organic superconductors, namely κ-Cu(NCS)2, κ-CuCN[N(CN)2] and κ-Cu[N(CN)2]Br salts, have been calculated using the superposedatom model and the numerical relaxation technique. For each salt positrons are distributed predominantly around the anion layers and have a little overlap with the TTF skeleton and the outer S atoms which are responsible for the conductivity.