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In the search for high performance n-type organic semiconductors (OSCs) a simple strategy might be substitution of aromatic CH groups for nitrogen heteroatoms. Here, we report the synthesis and characterisation of two novel N-heteroacene compounds, namely, 1,5,12-triazatetracene (TrAT1) and 2,5,12-triazatetracene (TrAT2). Their potential as n-type materials is evaluated against 5,12-diazatetracene (DAT) by UV/vis and EPR spectroscopy, cyclic voltammetry, DFT, single crystal X-ray diffraction and thin film characterisation. Increasing the number of N-heteroatoms was found to stabilise the HOMO and LUMO leading to electron affinities for TrAT1 and TrAT2 of ca. −4 eV. Both compounds were found to exhibit columns of co-facial π-stacked molecules. For TrAT1, molecules are also linked by hydrogen bonding, while the crystal structure of TrAT2 was found to be inherently disordered. Thin films of DAT, TrAT1 and TrAT2 were grown by organic molecular beam deposition (OMBD) and found to form discontinuous films, where TrAT1 exhibited a preferential orientation.

Single crystal X-ray diffraction, magnetic and 57Fe Mossbauer spectroscopic studies of a new iron(II)-based spin transition complex – [Fe(3-bpp)2](CF3COO)2 (bpp = 2,6-bis(pyrazol-3-yl)pyridine) are reported. The complex exhibits an incomplete thermal high spin (HS) low spin (LS) transition at ∼226 K which is not associated with any crystallographic transition. Only one of the two crystallographic iron(II) sites undergoes the spin transition, while the other HS site remains invariant of temperature down to 10 K. The origin of the incomplete spin transition is understood by analysing the nature of crystal packing below and above the transition temperature with special attention to the degree of distortion. The present study shows the role of the degree of distortion associated with the cations in the [Fe(3-bpp)2]2+ spin transition complexes.

We report the first example of a chiral BDH-TTP radical-cation salt. Chirality is induced in the structure via the use of a chiral spiroboronate anion where three stereocentres are present, one on each chiral ligand and one on the boron centre. Despite starting from a labile racemic mixture of BS and BR enantiomers, only one enantiomer is present in the crystal lattice. The anions pack in a novel double anion layer which is the thickest anion layer found in a BDH-TTP salt. This material is chiral and shows metallic behaviour down to at least 4.2 K.

A new bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF)-based salt with an organic magnetic anion, PO-CONHCH(cyclopropyl)SO3−, has been prepared (PO = 2,2,5,5-tetramethyl-3-pyrrolin-1-oxyl free radi...

Materials exhibiting both chirality and conductivity do not exist in nature and very few examples have been synthesised. We report here the synthesis of a chiral molecular metal which remains metallic down to at least 4.2 K. This material also exhibits room-temperature switching capabilities with a transition upon cooling below 10 °C.

Exploring new topological phenomena and functionalities induced by strong electron correlation has been a central issue in modern condensed-matter physics. One example is a topological insulator (TI) state and its functionality driven by the Coulomb repulsion rather than a spin-orbit coupling. Here, we report a "correlation-driven" TI state realized in an organic zero-gap system $\alpha$-(BETS)$_2$I$_3$. The surface metallic state that emerges at low temperatures exhibits characteristic transport properties of a gapless Dirac semimetal, evidencing the presence of a topological surface state in this compound. Moreover, we observe a topological phase switching between the TI state and non-equilibrium Dirac semimetal state by a dc current, which is a unique functionality of a correlation-driven TI state. Our findings demonstrate that correlation-driven TIs are promising candidates not only for practical electronic devices but also as a field for discovering new topological phenomena and phases., Comment: 36 pages including 10 figures

The exploration of dynamic molecular crystals is a fascinating theme for materials scientists owing to their fundamental science and potential application to molecular devices. Herein, a one-dimensional (1D) rhodium-dioxolene complex is reported that exhibits drastic changes in properties with the phase transition. X-ray photoelectron spectroscopy (XPS) revealed that the room-temperature (RT) phase is in a mixed-valence state, and therefore, the drastic changes originate from the mixed-valence state appearing in the RT phase. Another notable feature is that the mean square displacements of the rhodium atoms along the 1D chain dramatically increased in the RT phase, indicating a large-amplitude vibration of the Rh-Rh bonds. From these results, a possible mechanism for the appearance of the mixed-valence state in the RT phase was proposed based on the thermal electron transfer from the 1D d-band to the semiquinonato π* orbital coupled with the large-amplitude vibration of the Rh-Rh bonds.

A new family of six paramagnetic metals, namely, κ-(BDH-TTP)4CoCl4·(H2O)5 (I), κ-(BDH-TTP)4Co0.54Mn0.46Cl4·(H2O)5 (II), κ-(BDH-TTP)4MnCl4·(H2O)5 (III), κ⊥-(BDH-TTP)4CoBr4·(CH2Cl2) (IV), κ⊥-(BDH-TTP)4MnBr4·(CH2Cl2) (V), and κ⊥-(BDH-TTP)4MnBr4·(CH2Br2) (VI), has been synthesized and characterized by X-ray crystallography, four-probe conductivity measurements, SQUID magnetometry, and calculations of electronic structure. The newly discovered κ⊥-type packing motif of organic layers differs from the parent κ-type by a series of longitudinal shifts of BDH-TTP radical cations in the crystal structure. Salts I–VI form two isostructural groups: I–III (κ) and IV–VI (κ⊥). Salts I–III are isostructural to the previously discovered κ-(BDH-TTP)2FeIIIX4 (X = Cl, Br) even though the charge of FeX4– anions is half that of the MX42– (M = Co, Mn) anions. The tetrahedral anions are disordered in I–III but completely ordered in IV–VI. The type of included solvent molecule is solely determined by the anion size. The paramagnet...

Crystallisation from chiral electrolyte (R)-(−)-carvone has produced three new chiral semiconducting salts of BEDT-TTF from racemic anion tris(oxalato)chromate(III).

Electrocrystallisations of the chiral donor molecule S,S-bis(2-hydroxylpropylthio)ethylenedithiotetrathiafulvalene have produced a series of 1 : 1 semiconducting radical-cation salts with anions bromide, chloride, perchlorate and hexafluorophosphate. The flexibility and hydrogen bonding ability of the donor's chiral side chains lead to three quite different packing arrangements of donor cation pairs. Conductivity is maintained despite significant separations of donor cation pairs in some cases.

The new chiral TTF-based donor molecule bis(2-hydroxypropylthio)ethylenedithiotetrathiafulvalene has produced enantiopure R,R and S,S radical cation salts with the tetrafluoroborate anion as well as the nearly isostructural meso/racemate mixture. The enantiopure R,R or S,S salts are both 1:1 semiconducting salts with activation energies of 0.19–0.24 eV, both crystallising in the orthorhombic space group C2221. The semiconducting salt containing both meso and racemic donor cations has a very similar crystal structure but crystallising in the monoclinic space group C2/c (β = 91.39°) with similar S⋯S interactions but a smaller activation energy of 0.15–0.17 eV. This is in contrast to previous families of this type where the disordered racemate has a larger activation energy than its enantiopure salts.

The electrically conducting salt α-(BEDT-TTF)2(PO-CON(CH3)CH2SO3)·3H2O crystallized in the polar space group, Pna21. 2D conducting BEDT-TTF layers and anion layers alternate along the crystallographic c axis. In the crystal, permanent dipoles of all anions point along the c axis, providing a net crystal dipole moment.

Dependence of the superconducting transition temperature (T(c)) and critial superconducting pressure (P(c)) of the pressure-induced superconductor β-(BDA-TTP)(2)I(3) [BDA-TTP = 2,5-bis(1,3-dithian-2-ylidene)-1,3,4,6-tetrathiapentalene] on the orientation of uniaxial strain has been investigated. On the basis of the overlap between the upper and lower bands in the energy dispersion curve, the pressure orientation is thought to change the half-filled band to the quarter-filled one. The observed variations in T(c) and P(c) are explained by considering the degree of application of the pressure and the degree of contribution of the effective electronic correlation at uniaxial strains with different orientations parallel to the conducting donor layer.

A couple of naphthalenediimide 4 and 5 and series of perylenediimide derivatives 6–9 carrying TEMPO radical were prepared and their redox, FET, and magnetic properties were investigated. The radica...

The synthesis, crystal structure, and conducting properties of two new BEDT-TTF charge-transfer salts containing tris(oxalato)germanate(IV) anions are described. (BEDT-TTF)5[Ge(C2O4)3]2 (1) crystal...

The first chiral BEDT-TTF-tris(oxalato)metallate(III) salt has been crystallised from a solution containing the racemic anion in the chiral solvent (R)-(−)-carvone.

We have prepared a novel organic anionic weak acceptor, 2-aminomethylsulfo-3,5,6-trichloro-1,4-benzoquinone (1), as a PPh4 salt. Cyclic voltammetry indicates that its reduction potential is 0.53 V lower than that of chloranil. Electrocrystallisation with BEDT-TTF gave two salts, β - β -(BEDT-TTF)2(1)⋅0.5H2O (2) and β ″ - (BEDT-TTF)2(1)⋅CH3OH (3). Their crystal structures and physical properties are reported.

Hydroxymethyl-BEDT-TTF is converted by tosylation and elimination into exo-methylene-BEDT-TTF whose exocyclic double bond leads to a small increase in the oxidation potential, and from which radical cation salts with perchlorate and triiodide have been prepared, the latter showing semiconductor properties. Allyloxymethyl- and allylthiomethyl-BEDT-TTF, the first BEDT-TTF derivatives with an alkene in the side chain, have been prepared, along with a 1 : 2 radical cation perchlorate salt of the former, an insulator which contains a donor dication.

A new BEDT-TTF-based salt with an organic free radical TEMPO has been prepared. The salt consists of alternate layers of conducting and magnetic sheets, between which are short S(BEDT-TTF) …O(TEMPO) contacts. The magnetic susceptibility is well modelled by the combination of a 2D Heisenberg and a Curie–Weiss model with J = − 89 K and θ = + 0.05 K .

The synthesis of dihydrotetrathiafulvalene (DHTTF) donors and the preparation of their charge-transfer (CT) salts have been undertaken to develop new organic metals and superconductors. The molecular structures of methylenedithio-DHTTF (MDHT), 1,4-dioxane-2,3-diyldithio-DHTTF (DODHT), and methylmethylidenedithio-DHTTF (Me-MDHT) are secured by X-ray crystallographic analyses. These DHTTF donors provide CT salts characterized by a wide range of conducting behavior from semiconducting to metallic and superconducting. The crystal structures of CT salts from each category are described.

The synthesis and structural characterization of new liquid-crystalline compounds containing ferrocene, azo-aromatic and cholesteryl groups are reported. Taking into account the advantage brought by chirality, ferrocene and azo units, these structures could be good precursors for obtaining materials capable of responding to magnetic and electric fields or to UV-light exposure. The influence of each structural unit (ferrocene, cholesterol, azo aromatic core and flexible chain length) has been studied by comparing analogous compounds possessing the same structure but without the element being analyzed. Ferrocene is a three-dimensional bulky unit, so that, regardless of the substituents' nature, this unit could cause steric repulsions with neighboring molecules. These interactions could lead to a decrease of the transition temperature domain. Surprisingly, a decrease in the clearing point was not observed for the compounds discussed. This behavior was possible because ferrocene is connected to the mesogen via a flexible unit. As a consequence, both phenyl analogues and ferrocene derivatives presented liquid-crystalline properties with similarly high clearing points, but above the thermal stability of derivatives with azo groups. Their melting points depend on the way the molecules are packed, with different crystalline states being detected in the case of ferrocene derivatives. In order to explain the liquid-crystalline behavior of the compounds synthesized, molecular simulations were performed using the Hyperchem program. Copyright © 2005 John Wiley & Sons, Ltd.

The preparation and magnetic properties of organic radical anion salts derived from styrylpyrylium derivatives 1a and 2a are described and compared to those of the corresponding photo-dimers. The magnetic properties of the radical anions for TCNQ salt 1b and TCNQF4 salt 1c are rather different, showing antiferromagnetic interactions based on the 1-D Heisenberg model in the former, and ferromagnetic interactions in the latter. This difference is considered to be a result of the fairly large difference in their crystal structures. A considerable change in the magnetic properties was found between the radical anion salts of monomers and the corresponding photo-dimers, in which magnetic susceptibilities are largely diminished.

Organic salts derived from the styrylpyrilium systems as well as anthracene derivatives with TEMPO substituents were prepared and their structures and properties, especially magnetic properties wer...

The study of three kinds of non-tetrathiafulvalene (TTF) donors, 2,5-bis(1,3-dithian-2-ylidene)-1,3,4,6-tetrathiapentalene (BDA), 2,5-bis(1,3-dithiolan-2-ylidene)-1,3,4,6-tetrathiapentalene (BDH), and 2-(1,3-dithiolan-2-ylidene)-5-(1,3-dithian-2-ylidene)-1,3,4,6-tetrathiapentalene (DHDA), which contain the bis-fused 1,3-dithiole-2-ylidene unit instead of the TTF unit as a π-electron system, has been undertaken to develop new molecular-based organic superconductors, magnetic conductors, and organic metals. The BDA donor produces the superconducting SbF 6 , AsF 6 , and PF 6 salts. The κ-(BDH) 2 FeCl 4 salt is a paramagnetic organic metal stable down to 1.5 K, whereas β-(BDA) 2 FeCl 4 exhibits metallic conducting behavior with a sharp metal-to-insulator (MI) transition (T MI = 113K), and antiferromagnetic ordering with a Neel temperature of near 8.5 K. Several salts of DHDA, a hybrid of BDA and BDH, are found to be metallic.

A naphthalenediimide derivative 3a carrying TEMPO radical and azobenzene substituent was found to show photoresponsive magnetic as well as FET properties upon illumination. The alteration of its mo...

A new π-electron donor, 2,5-bis(13-dithian-2-ylidene)-1,3,4,6-tetrathia-pentalene (BDA-TTP), which contains no tetrathiafulvalene (TTF) molecule, produces a series ambient-pressure superconductors β-(BDA-TTP) 2 X (X = SbF 6 - , AsF 6 - , and PF 6 - ), in which the values of intermolecular overlap integrals suggest loose donor packing motifs.

A synthetic study of the dioxolane derivatives of methylenedithio(ethylenedithio)-tetrathiafulvalene (MET), bis(methylenedithio)tetrathiafulvalene (MT), and methylene-dithiotetrathiafulvalene, their dithiolane analogues, and the oxathiolane derivative of MET has been undertaken to explore new organic metals. A practically useful preparation of the biheterocycle-fused 1,3-dithiol-2-ones as building blocks for these dichalcogenolane-linked tetrathiafulvalene (TTF) donors has been realized via the newly developed BF 3 -promoted reactions. The effect of the additional linked dichalcogenolane ring on the electron-donating ability is investigated by cyclic voltammetry. An X-ray crystallographic analysis of the oxathiolane-linked MET reveals that its molecular structure is isostructural with that of its dithiolane analogue but not bulkier than that of its dioxolane analogue. Several of the present TTF donors have produced metallic charge-transfer materials, two of which are characterized by X-ray crystallography. In the crystal structure of the 7,7,8,8-tetracyanoquinodimethane complex of the dioxolane-linked MT that exhibits metallic-like behavior around room temperature, the donor molecules are stacked head-to-tail to form the dimers, which are connected by C-H…O hydrogen bonds. On the other hand, in the metallic AsF 6 salt of the dioxolane-linked MET stable down to 2.0 K, the donor molecules are stacked head-to-head to form two-dimensional sheets despite the dioxolane ring being perpendicularly attached to the MET molecule.

Several nitroxide radicals derived from 2,3,6,7-tetraalkoxy-9,10-anthraquinone core have been prepared and their magnetic, redox as well as battery properties are studied. Notably, one of the deriv...

κ-β′′-(BEDT-TTF)2(PO-CONHC2H4SO3) is the first stable metal containing an aminoxyl radical. The salt has both κ- and β′′-type donor sheets and exhibits metallic behavior down to 1.7 K. The magnetic susceptibility can be modeled by an alternate chain model with J1 = −0.80, and J2 = −0.69 K.

The heat capacities of crystalline and liquid p-bromochlorobenzene were measured by adiabatic calorimetry between 6 and 350 K. The crystal melts at 337.99 K with an enthalpy and an entropy of fusion of 18390 J mol-1 and 55.41 J K-1 mol-1, respectively. Neither an ordering phase transition nor a glass transition was detected in the solid state, contrary to an expectation based on the apparent symmetry of the molecule at room temperature due to an orientational disorder. The calorimetric entropy of the gas was estimated using the vapor-pressure data. A comparison with spectroscopic entropy based on a quantum chemical calculation shows that the PBCB crystal has a residual entropy of about Rln 2 (R: gas constant), which is compatible with the orientational disorder at room temperature. The absence of a sizeable anomaly due to a glass transition suggests two possibilities: an undetectably small thermal anomaly around the glass transition, or a glass-transition temperature higher than the temperature of fusion.

A glass transition due to the freezing of intramolecular motion is reported for κ-(ET) 2 Cu[N(CN) 2 ]Br around 105 K on the basis of heat capacity spectroscopy utilizing chopped-light a.c. calorimetry on a single crystal around 10 Hz. The glass transition temperature in the daily time scale (ca. 10 3 s), well corresponds to the temperature below which the physical properties including the superconducting transition temperature depends on the thermal history (e.g. cooling rate or annealing). The history dependence is reasonably resolved by taking into account the glass transition.

λ-(BETS)2GaBrxCl4-x [BETS = bis(ethylenedithio)tetraselenafulvalene; 0 ≤ x ≤ 2] is a molecular superconductor with strongly correlated conduction electrons. The electrical transport properties of λ-(BETS)2GaBrxCl4-x are drastically changed by varying the bromine content x or by applying pressure. At ambient pressure, the superconducting transition could be observed for x < 0.75. The pressure and x dependencies of Tc were examined. The M−H curve (M = magnetization; H = magnetic field) at 2 K indicated the almost perfect Meissner state of the superconducting phase of λ-(BETS)2GaCl4. The Hc1 is ∼8 Oe for H⊥ and 12 Oe for H∥, where H⊥ and H∥ are the magnetic fields perpendicular and parallel to the c axis, respectively. The magnetic susceptibility of λ-(BETS)2GaBrxCl4-x increases with decreasing temperature to ∼60 K, below which the susceptibility becomes x-dependent and tends to be suppressed with increasing x. The isotropic decrease of the static susceptibility at lower temperature observed in the insulatin...

SQUID magnetometry and transport measurements combined with crystal structure refinement have been used to examine the variation in superconducting properties (Tc and Meissner fraction) in the molecular superconductor β″-(BEDT-TTF)4[(H3O)Fe(C2O4)3]·C6H5CN on replacing the C6H5CN guest molecule with pyridine (C5H5N). Up to approximately 65% pyridine substitution there is only a small decrease in Tc and Meissner fraction but above that the superconductivity is suppressed.

A novel molecular complex of tetramethyltetrathiafulvalene (TMTTF) was prepared by the treatment with TiF4. The X-ray analysis reveals the exsistence of a trimer of TMTTF’s and a Ti2F102− anion in a triclinic unit cell of the dimension; a = 10.934(3), b = 12.798(2), c = 8.000(1) A, α = 103.86(1), β = 107.08(2), γ = 75.02(2)°. All the molecular planes of TMTTF are nearly parallel. The trimers stack parallel to the a axis, and the intertrimer interaction is estimated to be weak. A semiconductive behavior with a relatively large Seebeck coefficient was observed (ρ = 3 × 102 Ω cm, Ea = 0.26 eV, and S = −0.41 mV K−1 along the a axis). Weak electron spin resonance (ESR) absorption was observed to be characteristic of low-dimensional diffusive spin systems.

The molecular structure of 9,10-diethyl-9,10-diphospha-9,10-dihydroanthracene (PEPP) was determined by X-ray analysis. The central six-membered ring takes a boat conformation with two phosphorus atoms being the stem and stern, and the condensed tricyclic skeleton forms a butterfly-like structure. Of the two ethyl groups, which are attached to two P atoms in the central ring, the one is placed toward outside the skeleton (extra), and the other is located toward the inside of the ‘butterfly’ (intra). The observed redox potential of 0.63 V vs. Ag/AgCl suggests that this molecule has a fairly good electron-donating characteristics. From the spectroscopic observation and a quantum-chemical calculation, the donating orbital is estimated to be that of lone pair electrons at the P atom that attaches to the intra ethyl group.

The title compound, C6H4S4+·C9H16NO5S−, which includes an organic diamagnetic anion, was obtained unexpectedly by metathesis of the tetra­phenyl­phospho­nium salt of an organic free-radical anion, 2,2,6,6-tetra­methyl­piperidinyl­oxy-4-hydroxy-4-sulfonate, with (TTF)3(BF4)2 (TTF = tetra­thia­fulvalene).

The purely organic paramagnetic charge-transfer salt (TTF)3(PO-CON(CH3)C2H4SO3)2 was prepared. The anisotropic anion forms a head-to-head arrangement in the anionic layer, giving dual donor layers with different oxidation states. SQUID magnetometry indicates that spins are localized not only on the free radical (PO) but also on both TTF layers.

A trans-azobenzene derivative with a long alkyl chain and a TEMPO radical showed photo-induced isomerization to become the corresponding cis-isomer with a significant change of its intermolecular magnetic interaction from a weak ferromagnetic one based on the CW model to a relatively strong antiferromagnetic one based on the ST model with the J-value of 36.7 K.

A couple of naphthalenediimide derivatives carrying TEMPO radicals were found to exhibit n-type FET with mobilities up to 2.6×10−5 cm2/V·s as the first examples of spin-carrying acceptor systems wh...

A novel bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF)-based salt with an aminoxyl radical 2,2,5,5-tetramethyl-3-pyrrolin-1-oxyl (PO) has been prepared. The salt has α-type 2-D conducting sheets and is a semiconductor with ρ = 26 Ω·cm and E = 0.31 eV. The temperature dependence of the magnetic susceptibility suggests that both the aminoxyl radical and the BEDT-TTF layer have local spin moments at room temperature. Copyright © 2008 The Chemical Society of Japan.

Four kinds of TEMPO-substituted 1,4-benzoquinone derivatives were found to afford single-component CT crystals formed by the interactions between a benzoquinone ring and one or two TEMPO groups of ...

The reactions of TEMPO derivatives having a benzylideneamine unit with Cu(hfac)2 revealed unexpected formation of a complex consisting of 4-amino-TEMPO and Cu(hfac)2 and its crystal structure and magnetic properties showed marked difference from those of the corresponding Mn(hfac)2 complex and a complex derived from bis-TEMPO-substituted-ethylenediamine

The synthesis of DMDH-TTP [2-(4,5-dimethyl-1,3-dithiolan-2-ylidene)-5-(1,3-dithiolan-2-ylidene)-1,3,4,6-tetrathiapentalene] as a mixture of meso- and trans-forms has been accomplished, electrocryst...

The preparation of κ-(DHOT-TTP)2X (X = PF6, AsF6, and FeCl4) has been accomplished, which exhibit metallic conducting behavior down to low temperatures. A comparison of the values of the intermolec...

Organic crystals of the TCNQ or TCNQF4 radical anion salts derived from 2,4,6-triphenylpyridinium carrying TEMPO radical were obtained as a couple of different forms and their magnetic properties w...

The synthesis of DHOT-TTP, in which one sulfur atom of BDH-TTP [2,5-bis(1,3-dithiolan-2-ylidene)-1,3,4,6-tetrathiapentalene] is substituted by oxygen, has been accomplished. The DHOT-TTP donor possesses a less planar molecular structure than BDH-TTP, and gives a metallic AuI 2 salt stable down to 1.4 K, the crystal structure of which is elucidated.