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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...

Professor Peter Day FRS was born on 20 August 1938 in Kent (UK) and attended Maidstone Grammar School [...]

Peter Day’s research group reported the first molecular superconductor containing paramagnetic metal ions in 1995, β″-(BEDT-TTF)4(H3O)Fe(C2O4)3·C6H5CN. Subsequent research has produced a multitude of BEDT-TTF-tris(oxalato)metallate salts with a variety of structures and properties, including 32 superconductors to date. We present here the synthesis, crystal structure, and conducting properties of the newest additions to the Day series including the first superconductor incorporating the diamagnetic tris(oxalato)aluminate anion, β″-(BEDT-TTF)4(H3O)Al(C2O4)3·C6H5Br, which has a superconducting Tc of ~2.5 K. β″-(BEDT-TTF)4(H3O)Co(C2O4)3·C6H5Br represents the first example of a β″ phase for the tris(oxalato)cobaltate anion, but this salt does not show superconductivity.

Two novel salts containing the anion [Ni(mnt)2]− (mnt = maleonitriledithiolate) have been synthesized. The counter-ions, [Fe(II)(L1 or L2)2], are cationic complexes where L1 and L2 are methylated derivatives of 2,6-bis(pyazolyl)pyridine or pyrazine, which are similar to ligands found in a series of spin-crossover (SCO) complexes. Both salts are characterized by variable temperature single crystal X-ray diffraction and bulk magnetization measurements. Compound 1, [Fe(II)(L1)2][Ni(mnt)2]2 displays an incomplete and gradual SCO up to 300 K, followed by a more rapid increase in the high-spin fraction between 300 and 350 K. Compound 2, [Fe(II)(L2)2][Ni(mnt)2]2.MeNO2, shows a gradual, but more complete SCO response centered at 250 K. For compound 2, the SCO is confirmed by variable temperature Mössbauer spectroscopy. In both cases, the anionic moieties are isolated from each other and so no electrical conductivity is observed.

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.

New bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF)-, bis(ethylenediseleno)tetrathiafulvalene (BEST)- and bis(ethylenedithio)tetraselenafulvalene (BETS)-based organic charge-transfer (CT) salts&mdash, &alpha, (BEDT-TTF)3(HOC2H4SO3)2 (1), &beta, (BEST)3(HOC2H4SO3)2&middot, H2O (2) and &alpha, (BETS)2(HOC2H4SO3)&middot, H2O (3)&mdash, have been prepared. Salts 1 and 2 show semiconducting behaviour. Salt 3, which is almost isostructural to &alpha, (BETS)2I3, shows metallic behaviour down to 70 K and then shows a broader metal&ndash, insulator transition than that of &alpha, (BETS)2I3. The reason for the difference in behaviour is estimated by the comparison of the Madelung energies of the full set of patterns of possible donor&rsquo, s charge-ordered and anion&rsquo, s disordered states.

We newly constructed a thermal conductivity measurement system for single crystals of molecular compounds. This system enables us to measure the thermal conductivity of samples with the length of less than 1.0 mm. In order to evaluate the capability of detection of phase transitions occurred in molecule-based materials, we performed the thermal conductivity measurement of single crystals of organic conductors α-(BEDT-TTF)2I3 and κ-(BEDT-TTF)2Cu[N(CN)2]Br, where BEDT-TTF denotes bis(ethylenedithio)tetrathiafulvalene. From the temperature dependence of the thermal conductivity of α-(BEDT-TTF)2I3, we succeeded in observing the metal–insulator transition as a sudden drop of κ(T) at 135 K. In the temperature dependence of thermal conductivity of κ-(BEDT-TTF)2Cu[N(CN)2]Br, we could observe the increment of κ(T) at the metal-superconducting transition (Tc = 11.4 K). These results show that the newly developed system has high performance enough to detect various kinds of phase transitions in small crystals of molecular compounds.

A new Ni(dmit)2-based organic magnetic charge-transfer (CT) salt, (m-PO-CONH-N-methylpyridinium)[Ni(dmit)2]·CH3CN, where PO = 2,2,5,5-Tetramethyl-3-pyrrolin-1-oxyl free radical and dmit = 2-Thioxo-1,3-dithiole-4,5-dithiolate, was obtained, the crystal structure and magnetic properties of which are reported. Magnetic susceptibility of the CT salt obeys a combination of 1D ferromagnetic (1DF) Heisenberg (J1DF = +0.26 K) and Singlet-Triplet (ST) models (JST = -51.2 K) with mean field (MF) approximation (JMF = -6.7 K), suggesting that spins on the PO radicals form 1D ferromagnetic chains and spins on the Ni(dmit)2 monoanions forms spin dimers at low temperature, the latter of which was also confirmed by band calculations.

A new molecular superconductor, β”-(BEDTTTF)2[(H2O)(NH4)2Cr(C2O4)3].18-crown-6, has been synthesized from the organic donor molecule BEDT-TTF with the anion Cr(C2O4)3 3- . The crystal structure consists of conducting organic layers of BEDT-TTF molecules which adopt the β” packing motif (layer A), layers of NH4 + and Λ-Cr(C2O4)3 3- (layer B), layers of (H2O)(NH4)18- crown-6 (layer C), and layers of NH4 + and Δ-Cr(C2O4)3 3- (layer D) which produce a superstructure with a repeating pattern of ABCDABCDA. As a result of this packing arrangement this is the 2D superconductor with the widest gap between conducting layers where only a single donor packing motif is present (β”). Superconducting critical temperatures at ambient pressure observed by electrical transport and magnetic measurements are 4.0- 4.9 and 2.5 K, respectively. The strong 2D nature of this system, the broad transition to Tzero at 1.8K, and the transition of α of V ∝ Iα from 1 to 3 on I-V curves strongly suggests that the superconducting transition is very close to a Kosterlitz-Thouless transition. The magnetic field dependence of the superconducting critical temperature parallel to the conducting plane gives an upper critical field μ0Hc2// > 8 T, which is over the calculated Pauli-Clogston limit for this material.

A new BEDT-TTF-based salt with an organic free radical, α′-α′-(BEDT-TTF)2(PO-CONH-m-C6H4SO3)·H2O, has been prepared. The crystal structure consists of alternating donor and anion/water layers propagated along the c axis. The anisotropic radical anions form a head-to-head arrangement, which provides a permanent dipole moment. The effect on the nearest donor layer has been estimated to be 4.0 V. The salt has two crystallographically independent donor layers (A and B), one of which (A) is surrounded by the negative ends of the anion layer dipole whereas the B layers are bordered by the positive ends of the dipole. This structural feature suggests that layers A and B have different Fermi levels. To eliminate the imbalance, self-doping occurs whereby electron density is transferred from layer A to B. The temperature dependence of the magnetic susceptibility has 11.1% of extra Curie spins, from which a doping ratio of 12.7% has been estimated.

Magnetization measurements under pressure reveal that the external hydrostatic pressure significantly increases in the ferrimagnetic transition temperature, Tc, for A2Mn[Mn(CN)6] (A = K, Rb, Cs). In the case of monoclinic A = K and Rb, dTc/dp values are 21.2 and 14.6 K GPa–1, respectively, and Tc increases by 53 and 39%, respectively, from ambient pressure to 1.0 GPa. The cubic A = Cs compound also shows a monotonous increase with an initial rate of 4.22 K GPa–1 and about 11.4 K GPa–1 above 0.6 GPa, and an overall Tc increase by 26% at 1.0 GPa. The increase in Tc is attributed to deformation of the structure such that the MnII—N≡C angle decreases with increasing pressure. The smaller the alkali cation, the greater the decrease in the MnII—N≡C angle induced by pressure and the larger the increase of dTc/dp. This is in accordance with the ambient-pressure structures for A2Mn[Mn(CN)6] (A = K, Rb, Cs), which have decreasing MnII—N≡C angles that correlate to the observed increasing Tcs as K > Rb > Cs. The larg...

The chiral TTF-based donor molecule bis(2′-hydroxylpropylthio)(ethylenedithio)tetrathiafulvalene (BHPT-EDT-TTF) has produced enantiopure R,R and S,S radical-cation salts with polyiodide anions I3− and I82−. Enantiomorphic 6 : 6 donor : I3 phases grown from either the R,R or S,S donor are semiconducting with similar activation energies of 0.24–0.30 eV and 0.22–0.23 eV, respectively, and contain three unique face-to-face donor pairs whose relative orientation is determined by side chain conformations and hydrogen bonding. Racemic material under the same conditions gave an insulating centrosymmetric phase with R,R and S,S donor cations in a face-to-face pair partnered with an octaiodide dianion, and with a ca. 3 : 1 disorder between the enantiomers. Enantiopure BHPT-EDT-TTF yielded two further insulating crystalline phases of composition 2 : 2 with triiodide and 2 : 1 with octaiodide.

We investigate low-temperature electronic states of the series of organic conductors β'' - [bis(ethylenedithio)tetrathiafulvalene] 4[(H3O)M(C2O4)3] G, where M and G represent trivalent metalions and guest organic molecules, respectively. Our structural analyses reveal that the replacement of M and G give rise to systematic change in the cell parameters, especially in the b-axis length, which has a positive correlation with the superconducting transition temperature Tc. Analysis of temperature and magnetic field dependences of the electrical resistance including the Shubnikov–de Haas oscillations elucidates that the variation of charge disproportionation, the effective mass, and the number of itinerant carriers can be systematically explained by the change of the b-axis length. The changes of the transfer integrals induced by stretching/compressing the b axis are confirmed by the band calculation. We discuss that electron correlations in quarter-filled electronic bands lead to charge disproportionation and the possibility of a novel pairing mechanism of superconductivity mediated by charge degrees of freedom.

This work describes the synthesis of two novel functionalised 2,6-bis(pyrazol-1-yl)pyridine (bpp) ligands, namely 2,6-bis(pyrazol-1-yl)pyridine-4-carbothioamide (bppCSNH2) and N-methyl-2,6-bis(pyrazol-1-yl)pyridine-4-carbothioamide (bppCSNHMe). The corresponding solvated or non-solvated Fe(II) salts, [Fe(bppCSNH2)2]X2 and [Fe(bppCSNHMe)2]X2 (X = BF4− or ClO4−) were synthesised and their properties measured by SQUID magnetometry, Evans NMR, differential scanning calorimetry and single crystal X-ray diffraction. In the solid state [Fe(bppCSNH2)2]2+ salts persist in the low spin state below 350 K. The structure of [Fe(bppCSNH2)2](BF4)2·2MeNO2 shows a network of intermolecular interactions responsible for the low spin state stabilisation, relative to the prototypical [Fe(bpp)2]2+ spin crossover (SCO) salts. By contrast the complexes of bppCSNHMe both display abrupt SCO above 300 K. [Fe(bppCSNHMe)2](BF4)2·MeNO2 requires solvent loss before SCO can be observed centred at 332 K. The non-solvated [Fe(bppCSNHMe)2](ClO4)2 shows SCO centred at 325 K. Analysis of solvated and non-solvated crystal structures suggests that cooperativity is facilitated by thioamide-group interactions with neighbouring pyrazolyl and pyridyl moieties.

The series of salts β′′-(BEDT-TTF)2[(H2O)(NH4)2M(C2O4)3]·18-crown-6 show ambient-pressure superconductivity when M = Cr, Rh. Evidence indicates that the previously reported Cr and Rh salts show a bulk Berezinski–Kosterlitz–Thouless superconducting transition. The isostructural ruthenium and iridium salts are reported here. The Ir salt represents the first radical-cation salt to contain a 5d tris(oxalato)metalate anion. The Ru and Ir salts do not show superconductivity but instead undergo a broad chemically induced metal to insulator transition at 155 K for ruthenium and at 100 K for iridium. The c axes of the Ru and Ir salts are much shorter than those of the Rh and Cr salts. Thus, the more stable metallic state of the Cr and Rh salts is associated with the more strongly 2D electronic systems. The different low-temperature behavior of the Ru and Ir salts, which exhibit a smaller interlayer spacing, could originate from a structural change in the anionic layer which thus can be easily transmitted to the donor layers and generate a localized state. However, another possibility is that it originates from Berezinski–Kosterlitz–Thouless effects., This work has been supported by a Royal Society Leverhulme Trust Senior Research Fellowship, and the JSPS (KAKENHI Grant Number JP17H01144) and Royal Society (Research Grants (RG100853 and RG081209), International Exchange Scheme (IE130367 and IE150152), and International Joint Project (JP0869972)). L.M. thanks the Royal Society and Leverhulme Trust for a Senior Research Fellowship. J.R.L. and L.M. thank Nottingham Trent University for Ph.D. funding. E.C. acknowledges support by the MICIU (Spain) through Grant PGC2018-096955-BC44 and the Severo Ochoa Centers of Excellence Program (Grant SEV-2015-0496) as well as by the Generalitat de Catalunya (2017SGR1506).

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...

The temperature dependence of the ac heat capacity of a molecule-based superconductor κ-(BEDT-TTF)2Cu(NCS)2 under external pressures and with magnetic fields is reported. A peak structure in C p T −1 due to the superconductive transition was observed around 9 K at ambient pressure. This peak is suppressed by applying magnetic fields up to 7 T. The systematic decrease in the transition temperature with the increase in external pressure is confirmed by thermodynamic measurements under 0.15, 0.30 and 0.45 GPa. Through the analysis of the peak shape of the thermal anomaly, it is suggested that the gradual suppression of the coupling strength of the superconductivity occurs with the increase in pressure. This feature is consistent with the argument based on the chemical pressure effect in the superconductive phase of κ-(BEDT-TTF)2 X system, where X denotes mono-valence counter anions. The result demonstrates that the appearance of the Fermi-liquid character produced by applying pressure in the dimer-Mott phase diagram affects the nature and the coupling feature of the superconductivity. Importance of high-pressure heat capacity for molecule-based compounds is emphasized.

The appearance of electron correlations–induced glassy state of low-energy phonons in the non-dimeric organic charge transfer salt in [Formula: see text]-(BEDT-TTF)2CsZn(SCN)4 is considered as a strong evidence of charge lattice coupling in molecular charge transfer salts. We discuss the temperature and the magnetic field dependences of the heat capacity of this salt in terms of the soft potential model to describe the thermodynamic properties of enhanced phonons that occur in molecular glasses. The evaluated [Formula: see text] term of [Formula: see text]-(BEDT-TTF)2CsZn(SCN)4 is about 30 mJ K[Formula: see text] mol[Formula: see text], which is much larger than other charge transfer salts described by the low-temperature approximation of the Debye model. The magnetic fields dependence of the boson peak is almost negligible, but the low-energy term, for example, in the temperature-linear term of heat capacity shows a slight change, probably due to the small amount of localized spin moments. The comparison with other systems is also performed.

The structure and properties of a new semiconducting BEDT-TTF-based charge-transfer salt containing the magnetic monoanion octamethylferrocenedisulfonate (–O3SC5( CH3)4Fe+C5(CH3)4-SO3 – (ofds)), -(BEDT-TTF)5(ofds)2 is described (BEDT-TTF = bis(ethylenedithio)tetrathiafulvalene). The salt is a semiconductor with RT = 5.6  103 ·cm and Ea = 0.11 eV. There are two types of spins not only on the ferrocenyl parts but also the 2D donor layers. The former and latter spins obey Curie-Weiss (C = 0.721 emu K mol-1and  = -5.5 K) and 2D Heisenberg (J2DH = - 80.3 K) models, respectively.

The synthesis, crystal structure and resistivity of a new semiconducting BEDT-TTF radical-cation salt containing the tris(oxalato)germanate(IV) anion is reported. BEDT-TTF 4 [Ge(C 2 O 4 ) 3 ].0.5dichloromethane crystallizes in the space group P 2 1 / c, a = 18.322(7), b = 11.919(4), c = 32.746(11) A, β = 105.797(5)°, V = 6881(4) A 3 , T = 295(1) K, Z = 4. Electrical resistivity measurements show that BEDT-TTF 4 [Ge(C 2 O 4 ) 3 ].0.5dichloromethane is a semiconductor with an activation energy of 0.224 eV and room temperature resistivity of 212 Ω cm.

In order to develop a kind of dual redox system with rechargeable battery property having potential high charge density, eight disulfide compounds carrying nitroxide radical have been prepared. Reflecting their multi-redox nature observed in their cyclic voltammetry data, they exhibit multi-step charge–discharge profiles with fairly large capacities over 200 Ah kg−1 for the first discharging processes. The Curie–Weiss type behaviors or 1D Heisenberg type profiles found for the respective radical compounds could be understandable by investigating the clarified crystal structures of four compounds (3, 4, 7, and 8) among them.

An experimental technique for controlling cooling rate at low-temperature region in the heat capacity measurements was developed, and results of the heat capacity measurements of organic superconductor (TMTSF)2ClO4 cooled down with various cooling rates are presented. We succeeded in obtaining heat capacity data for a single piece of a crystal down to 0.7 K to study electronic states attained with slow cooling rates to extremely high cooling rate up to 500 K min−1. In the case of slow cooling at 0.17 K min−1, we observed a distinct peak of the superconductive transition which is almost consistent with previous results. The fraction of superconductive part is reduced in faster cooling rates, and no distinct peak structure in C p T −1 versus T 2 plot is observed around T c in the data of higher rate than 1.3 K min−1. In the rapid cooling region of 200 K min−1, clear reduction in electron density of states reflected in the change of the normal state γ value in the electronic heat capacity was observed. The sample shows an insulating character with a charge gap in the case of rapid cooling of 500 K min−1. We also discuss the feature of thermal anomaly related to the anion ordering around 24 K. A kind of glass-like freezing in residual conformational dynamics is suggested from the step-like decrease in C p T −1 around 19 K.

Radical-cation salts of BEDT-TTF with chiral anions provide the opportunity to combine chirality with conductivity in the same molecular material. We report here two salts, (BEDT-TTF)3NaAl(C2O4)3·nitromethane and (BEDT-TTF)3(NH4)0.83Cr1.17(C2O4)3·nitromethane. The former crystallises in space group P21 and the latter in P212121. The use of nitromethane alone as the electrolyte for electrocrystallisation produces no crystals, but the addition of chiral (R)-(–)-carvone yields crystals of these two new chiral radical-cation salts of BEDT-TTF through chiral induction from racemic tris(oxalato)aluminate(III) and tris(oxalato)chromate starting materials. The honeycomb anion layers in these salts contain a single enantiomer of tris(oxalato)metallate and creates hexagonal cavities that are smaller than those found in the superconducting β″ salts in this tris(oxalate)metallate family, which gives preference for smaller solvents to be included, such as nitromethane. The chromium salt has a non-stoichiometric composition of the anion layer, which provides an electron doping effect to the donor layer.

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.

This article reports a family of new radical-cation salts of bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) with tris(oxalato)rhodate: three salts with the formula β′′-(BEDT-TTF)4[(cation)Rh(C2O4)3]·solvent (solvent = fluorobenzene, chlorobenzene, or bromobenzene) and one with the formula pseudo-κ-(BEDT-TTF)4[(NH4)Rh(C2O4)3]·benzonitrile. We report here the syntheses, crystal structures, electrical properties and Raman spectroscopy of these new molecular conductors. The bromobenzene salt shows a decrease in resistivity below 2.5 K indicative of a superconducting transition and a Shubnikov–de Haas oscillation with a frequency of 232 T and effective mass m* of 1.27me.

We report a novel multilayered organic–inorganic hybrid material, β″-(BEDT-TTF)2[(H2O)(NH4)2Rh(C2O4)3]·18-crown-6. This is the first molecular superconductor to have a superlattice with layers of both BEDT-TTF and 18-crown-6 and also the first with the anion tris(oxalato)rhodate. This is the 2D superconductor with the widest gap between conducting layers, where only a single donor packing motif is observed (β″). The strong 2D nature of this system strongly suggests that the superconducting transition is a Kosterlitz–Thouless transition. A superconducting Tc of 2.7 K at ambient pressure was found by transport measurements and 2.5 K by magnetic susceptibility measurements.

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.

We report the glass-like thermal conductivity behavior of two charge-glass (CG) formers in θ-type organic semiconductors composed by bis(ethylenedithio)tetrathiafulvalene (abbreviated as BEDT-TTF) ...

While an addition product was formed by the reaction of AZADO (2-azaadamantane N-oxyl) with TCNQF4 (2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane), the reaction of AZADO with thiourea provided an inclusion compound, in which AZADO molecules are incorporated in cylindrical channels formed by thiourea molecules.

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.

We report high-field magnetotransport measurements on β-(BEDT-TTF) 4 [(H 3 O)M(C 2 O 4 ) 3 ]. solvent, where M=Ga 3+ , Cr 3+ and Fe 3+ and solvent=C 5 H 5 N. In spite of their differing transition metal-ions, M, the three compounds exhibit similar magnetic quantum oscillation spectra superimposed on a positive magnetoresistance. At least four independent quantum oscillation frequencies have been identified, corresponding to two different hole and electron pockets of the Fermi surface which follow the rules of a compensated metal. Observation of the small pockets could be the result of the Fermi surface reconstruction induced by a possible density wave. The effective masses are very similar for different samples and for different pockets range between m eff 0.5 - 1.1 m e whereas the Dingle temperatures varies between T D 1.4 - 4 K. At low temperature, the longitudinal magnetoresistance violates Kohler's rule, suggesting that the interlayer transport in these quasi-2D systems cannot be related to a single scattering time and that the disorder plays an important role.

We have synthesized the first examples of radical-cation salts of BEDT-TTF with chiral borate anions, [B(malate)2](-), prepared from either enantiopure or racemic bidentate malate ligands. In the former case only one of two diastereoisomers of the borate anion is incorporated, while for the hydrated racemic salt one racemic pair of borate anions containing a R and a S malate ligand is incorporated. Their conducting and magnetic properties are reported. The tight-binding band calculation indicates that the chiral salt has an effective half-filled flat band, which is likely to be caused by the chiral structural feature.

A series of aryl-substituted naphthalenediimide derivatives that contain nitroxide radicals were prepared and their crystal structures were elucidated. Much stronger charge-transfer interactions were present in the derivatives with perfluorobenzene substituents than those with phenyl or 4-fluorophenyl substituents. These interactions result in the formation of single-component charge-transfer complexes by self-assembly of the naphthalenediimide derivatives to provide black crystals. As a consequence, the naphthalenediimide derivatives with perfluorobenzene substituents have better field-effect transistor (FET) properties than the other derivatives.

Organic molecular conductors with a strongly correlated electron system, in which the itinerancy of electrons (or holes) and the electron correlation (U/W, U, the on-site Coulomb repulsion, W, the bandwidth) compete with each other, are promising candidates for achieving superconductivity and also for exploring remarkable physical properties induced by external stimuli such as pressure, light, voltage and current. Our synthetic approach to the construction of strongly correlated organic electron systems is based on chemical modifications to the donor molecule BDH-TTP [2,5-bis(1,3-dithiolan-2-ylidene)-1,3,4,6-tetrathiapentalene] capable of producing metallic CT (charge-transfer) salts stable down to low temperatures (4.2–1.5 K). This aims at enhancing the electron correlation in the itinerant electron system by decreasing the bandwidth. Chemical modifications of BDH-TTP such as ring expansion of two outer dithiolane rings, replacement of one sulfur atom in an outer dithiolane ring with an oxygen atom and introduction of two methyl substituents into an outer ditiolane ring led to BDA-TTP [2,5-bis(1,3-dithian-2-ylidene)-1,3,4,6-tetrathiapentalene], DHOT-TTP [2-(1,3-dithiolan-2-ylidene)-5-(1,3-oxathiolan-2-ylidene)-1,3,4,6-tetrathiapentalene] and DMDH-TTP [2-(4,5-dimethyl-1,3-dithiolan-2-ylidene)-5-(1,3-dithiolan-2-ylidene)-1,3,4,6-tetrathiapentalene], respectively. In this review, the physical properties and the crystal and electronic structures of molecular conductors derived from these donor molecules will be described.

A novel organic dianion, N,N'-Disulfo-1,4-benzoquinonediimine (1) has been prepared, which is a strong electron acceptor. The reduction potential of the PPh4 salt indicates that 1 is a stronger acceptor than DDQ (2,3-dichloro-5,6-dicyano-1,4-benzoquinone). The dianionic acceptor provided a BEDT-TTF salt, (BEDT-TTF)41·3H2O, the structures and physical properties of which are reported.

Several ferrocene derivatives (1–6) carrying nitroxide radical were prepared as dual redox compounds. They have distorted molecular structures and exhibit oxidation potentials based on both ferrocene and nitroxide groups except 4. The multi-step charge–discharge processes are discriminated for mono-substituted derivatives with the first discharge capacity up to 400 Ah kg−1 for imino-derivative 3, while relatively characterless profiles are observed for bis-substituted derivatives 4 and 6 with capacity over 300 Ah kg−1.

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.

An anionic weak acceptor, 2-sulfo-1,4-benzoquinone, has provided a new BEDT-TTF (bis(ethylenedithio)tetrathiafulvalene) salt (BEDT-TTF)2(2-sulfo-1,4-benzoquinone)·H2O. Single crystal X-ray analysis indicates that the unit cell has two crystallographically independent donor layers, one of which has a β″-type packing motif and the other being disordered. Population analysis and SQUID magnetometry suggests that non-β″-layer has an α‴-type packing motif. The dual-layered salt shows metallic behavior with a metal–insulator transition at 90 K.

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...

Thermodynamic discussion on the physical properties around the Mott boundary of the dimer-Mott system of [Formula: see text]-type (BEDT-TTF)2X system, where BEDT-TTF is bis(ethylenedithio)tetrathiafulvalene and X denotes monovalent counter anions is performed by heat capacity measurements of the [Formula: see text]-(d[n,n] BEDT-TTF)2Cu[N(CN)2]Br of which donor molecules are partially deuterated. We compare temperature dependences of heat capacity of d[2,2], d[3,3] and d[4,4] compounds (defined as shown in Fig. 1) obtained in rapidly cooled and slowly cooled conditions. While the heat capacity of d[2,2] compound shows cooling rate dependence with the slight change of the absolute values Cp between 25 K and 50 K, the temperature dependences of the other compounds do not give drastic change by changing the cooling rate. The compounds of d[2,2] and d[3,3] located very close to the Mott boundary show peculiar hump structure in the C[Formula: see text]T[Formula: see text] that is related to the existence of a kind of lattice instability region around the first-order phase boundary. The temperature and chemical pressure dependences of the anomalous region are discussed in terms of the phase diagram in which the Mott boundary has peculiar rounding at low-temperature region.

We have prepared new organic anionic acceptors, Br2XQNHCH2SO3− (2: X=Br, 3: X=BryCl1−y (y≈0.5), 4: X=Cl; Q=1,4-benzoquinone), that possess both an electron acceptor part (1,4-benzoquinone) and an anionic part (sulfonate). The reduction potentials of the PPh4 salts of 2, 3 and 4 are −0.45, −0.45 and −0.46 V (vs. SCE in CH3CN), respectively. The results indicate that they are weaker acceptors than chloranil (−0.13 V) and bromanil (−0.12 V). Each anionic acceptor (AA) provided two BEDT-TTF salts, β-(ET)5(AA)2·DCE·zH2O and λ-(ET)2(AA)·CH3OH (AA=2, 3, or 4; z=2: 0.97, 3: 0.83 and 4: 0.40). The structures and transport properties of the salts are reported.