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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.

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.

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.

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

An organic anion, 2-bromoethanesulfonate (BrC2H4SO3−), provides one bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) and two bis(ethylenedithio)tetraselenafulvalene (BETS) salts, the compositions of which are β’’-β’’-(BEDT-TTF)2BrC2H4SO3 (1), β’’-β’’-(BETS)2BrC2H4SO3 (2), and θ-(BETS)2BrC2H4SO3 (3), respectively. Compound 1 shows a metal–insulator transition at around 70 K. Compound 2 is isomorphous to 1, and 3 is polymorphic with 2. Compounds 2 and 3 show metallic behavior at least down to 4.2 K. The pressure dependence of the electrical resistivity of 1 is also reported.

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.

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 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.

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 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.

Series of radical salts derived from a 2,4,6-triphenylpyridinium (TPP) carrying TEMPO-substituent and transition metal complexes were prepared by the anion exchange of the TPP–TEMPO tetrafluoroborate with [n-Bu4N][Ni(dmit)2], [n-Bu4N]2[Pd(dmit)2], [n-Bu4N]2[Pt(dmit)2], [n-Bu4N][Ni(mnt)2], or [n-Bu4N]2[Ni(mnt)2] to give crystals with different structural features. While weak antiferromagnetic interactions of the Curie–Weiss behavior of S = 1/2 spin are predominantly observed in the salts of Pd(dmit)2, Pt(dmit)2 and Ni(mnt)2, the magnetic behavior of 1:1 Ni(dmit)2 salt can be explained by the additional contribution from the spins on Ni(dmit)2 anions (χ − χTEMPO), obeying the 2D Heisenberg model. A couple of the oxidized salts, [TPP][Ni(dmit)2] as well as [TPP]2[Pd(dmit)2], exhibit semi-conducting properties with relatively high room temperature conductivities.

Structures and properties of three Mn(hfac)2 (hfac = hexafluoroacetylacetonate) complexes derived from two kinds of bis-TEMPO (2,2,6,6-tetramethylpiperdinyl-1-oxy)-substituted diamines are reported. In a complex derived from bis-TEMPO-substituted ethylenediamine, the unit is coordinated to the manganese atom to afford a spin system with weak antiferromagnetic intermolecular interactions, while apparent ligations of both TEMPO groups to the metal atom are observed in a couple of Mn(hfac)2 complexes derived from bis-TEMPO-substituted piperadine to result in spin systems with fairly large antiferromagnetic interactions.

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.

Series of organic radical compounds with trans -azobenzene chromophore have been prepared to see the photo-induced isomerizations to the corresponding cis -azobenzenes and the possible changes of intermolecular magnetic interactions based on the isomerizations. Although the cis -isomers with p -nitro- or p -dimethylamino-substituent on one side and TEMPO-attached long alkoxy group on the other side could not be isolated as stable solids, the cis -isomers of unsubstituted derivatives at 4-position and with a TEMPO group at 4′-position have successfully been isolated as relatively stable solid materials showing apparent changes of intermolecular magnetic interactions. A couple of Mn(hfac) 2 complexes derived from isomeric TEMPO-substituted esters were found to be reluctant to the photo-isomerization upon irradiation.

Several radical salts derived from a TEMPO-substituted 2,4,6-triphenyl pyridinium have been prepared by replacing the fluoroborate anion with an anionic metal-complex such as Ni(dmit) 2 , Pd(dmit) 2 or Ni(mnt) 2 and their structures and physical properties were investigated. The oxidized salts of the Ni(dmit) 2 as well as Pd(dmit) 2 complexes show semi-conducting properties with relatively high conductivities and low activation energies.

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 .

We have prepared eight TEMPO-containing anions TEMPO – A – CO – ( n - ) C 6 H 4 S O 3 - (n = o, m, p for A = NH (N1, N2, N3), n = o, p for A = NCH3 (M1, M3), and n = o, m, p for A = O (O1, O2, O3)) as PPh4 salts. Metathesis of their salts with (TTF)3(BF4)2 gave their TTF salts. Electrocrystallization of BEDT-TTF with PPh4 · M1 yielded the α-(BEDT-TTF)3(M1)2 · 8H2O salt. We report their crystal structures, electrical resistivities, and magnetic properties. The relation between crystal structures and physical properties are discussed.

Series of monoradicals and biradicals having an aromatic core on one hand and long alkyl groups on the other hand have been prepared. It was found from their magnetic data that the biradical compounds having aromatic cores (azoxy, or azo) and long alkyl groups with TEMPO radicals at their ends showed fairly large antiferromagnetic interactions ( J = −34, −39 K) being well expressed by ST model, while only weak antiferromagnetic interactions were observed in the corresponding PROXYL derivatives together with the corresponding monoradicals. The change of intermolecular magnetic interactions based on the structural change from trans - to cis -isomer by irradiation was found to be possible in a couple of azobenzene derivatives with an aminoxyl radical.

In order to investigate molecular conductors containing magnetic anions, πd-interactions Jπd and dd-interactions Jd, have been estimated from the overlap of molecular orbitals by using the relation J = −2t2/U. In the present paper this method is applied to a new antiferromagnetic superconductor (BDA-TTP)2FeCl4, a semiconducting ferrimagnet (EDT-TTF-VO)2FeBr4, and a β′-type semiconductor (BEDT-TTF)3(MnCl4)2. The dd interaction of (BDA-TTP)2FeCl4 is as large as λ-(BETS)2FeCl4, guaranteeing the relatively high TN. The small Jπd of this compound is related to the steric effect of the outer trimethylene groups of the donor. The observed ferrimagnetism in (EDT-TTF-VO)2FeBr4 is related to the localization of the π-electrons associated with the charge order, as well as the fairy large πd-interactions bridging different anions. (BEDT-TTF)3(MnCl4)2 is a characteristic compound due to the extraordinarily large πd-interactions to the donors incorporated in the anion layer.

Five TEMPO-containing anions TEMPO - CONA ( CH 2 ) n SO 3 - (H0−, A = H, n = 0; H1−, A = H, n = 1; H2−, A = H, n = 2; H3−, A = H, n = 3; M2−, A = CH3, n = 2) have been prepared as PPh4 salts. So far three TTF salts ((TTF)(H1) · 2H2O, (TTF)(H2) · H2O, and (TTF)(M2) · 0.50H2O), one TMTSF salt ((TMTSF)(H1) · 2H2O · PhCl), and one BEDT-TTF salt (α-(BEDT-TTF)5(H1)2 · 6H2O) have been obtained. Their crystal structures, electrical resistivities, and magnetic properties are reported.

New organic functional anions that includes the ferrocenyl group, CpFeCp-CONHCH 2 SO 3 − and Fe(Cp-CONHCH 2 SO 3 − ) 2 , are prepared as tetraphenylphosphonium (PPh4) salts. They reacted with (TTF) 3 (BF 4 ) 2 to give TTF monocation salts. The X-ray analyses indicate that for all salts TTF forms a dimer which is separated by the relatively larger anions. The oxidation reaction of (PPh 4 )(CpFeCp-CONHCH 2 SO 3 ) with I 2 gave the Zwitter-ion, CpFe + Cp-CONHCH 2 SO 3 − , which shows a Curie-Weiss behavior ( C = 0.800 emu·K/mol, θ = −1.13 K) with weak antiferromagnetic interaction. This magnetic moment is found to be attributed to the ferrocenyl radical.

We report here four novel purely organic magnetic conductors containing common electron donors together with an organic anion including an organic free radical, (TTF)(TEMPO-NHCOCH 2 SO 3 )·0.5H 2 O ( 1 ), (TMTSF)(TEMPO-NHCOCH 2 SO 3 )·2H 2 O ( 2 ), (BEDT-TTF) 3 (TEMPO-NHCOCH 2 SO 3 ) 2 ·2H 2 O ( 3 ), and α-(BEDT-TTF) 3 (TEMPO-NHCOCH 2 SO 3 ) 2 ·6H 2 O ( 4 ). The TTF complex was prepared by metathesis of (TTF) 3 (BF 4 ) 2 and the PPh 4 salt of the anion ( 5 ). The other complexes were obtained by electrocrystallization of the corresponding donors with the salt 5 as an electrolyte. Crystal structures of 2–4 have been solved. The salts 1 and 2 show relatively high resistivities (>10 7 and 5 × 10 3 Ω·cm), whilst the BEDT-TTF salts 3 and 4 have rather low room temperature resistivities (1.2 and 5.1 Ω·cm) with small activation energies (0.041 and 0.050 eV). The magnetic behavior of complex 1 obeys the Curie-Weiss law ( C = 0.379 emu·K/mol and θ = −3.29 K) and those of the other complexes obey the 1-D Heisenberg model ( C / J = 0.366/−0.32 for 2 , 0.373/−0.81 for 3 , and 0.380 emu·K·mol −1 /+0.42 K for 4 ). The relationships between the crystal structures and the physical properties are discussed.

The TaF 6 and FeBr 4 salts of BDA-TTP [2,5-bis(1,3-dithian-2-ylidene)-l,3,4,6-tetrathiapentalene] have been prepared and characterized as β-(BDA-TIP) 2 TaF 6 and β-(BDA-TIP) 2 FeBr 4 , respectively. The crystal structure of β-(BDA-TTP) 2 TaF 6 is isostructural to those of the ambient-pressure superconductors β-(BDA-TTP) 2 X (X = SbF 6 , AsF 6 and PF 6 ), but this salt undergoes an Ml (metal-to-insulator) transition instead of a superconducting transition at ambient pressure. The β-(BDA-TTP) 2 FeBr 4 salt, which is isomorphous to the superconductors β-(BDA-TTP) 2 MCl 4 (M = Fe and Ga) under applied pressures, exhibits a phase transition near 170 K and antiferromagnetic ordering with the Neel temperature (T N ) of about 9.5 K at ambient pressure.

We report the structures and physical properties of new β′-(BEDT-TTF)[Fe(oxalate)]·G salts where A = HO, G = PhCl; A = Rb G = Pyridine. The structure of the PhCl salt is isomorphous with β′-(BEDT-TTF)[(HO)M(oxalate)] with other guest molecules. PhCl is ordered in die hexagonal pockets formed by the [(HO)Fe(oxalate)] layer. The electrical conductivity is metallic down to 100 K, below which the resistivity increases with decreasing temperature. The specific conductivity at room temperature is about 10 S/cm. We also report the salt β′-(BEDT-TTF) [RbFe(oxalate)]·Pyridine where Rb replaces HO. The electrical resistivity shows metallic behavior down to 100 K. and turns up gradually to a maximum at 65 K below which the system re-enters the metallic state down to liquid helium temperature. Neither salt shows superconductivity down to 2 K. In addition, other new β′-(BEDT-TTF)[(HO)M(oxalate) ]·salts with M = Cr, Ga, Fe; G = CHCl , CHClBr, CHBr are also reported. © 2005 Elsevier B.V. All rights reserved.

Heat capacities of crystalline charge-transfer (CT) complexes between trans-stilbene (STB) and tetracyanoquinodimethane (TCNQ) or (TCNQ)F4 were precisely measured below room temperature by adiabatic calorimetry. Although orientational disorder is seemingly absent, a glass transition due to freezing of the crankshaft motion is observed in STB-(TCNQ)F4 around 240 K as in the case of highly disordered STB-TCNQ around 250 K. Assessment of the degree of CT by IR and structural methods indicates that STB-(TCNQ)F4 is not a fully but weakly (only partially) ionic complex with a similar degree of CT of 0.1-0.2 to that in STB-TCNQ, despite the large difference in acceptor ability.

A novel ferrocene-containing dianion, Fe(C5H4–CH(CH3)NHCOCH2SO3–)2 (1), has been prepared. The oxidation potential of the PPh4 salt is + 0.35 V (vs. SCE in PhCN), indicating that it is a stronger donor than TTF (tetrathiafulvalene) by + 0.03 V. The dianion provided a TTF salt, the structure and physical properties of which are reported.

We have prepared two dmit-based salts with a stable organic radical-substituted ammonium cation, (PO-CONH-C2H4N(CH3)3)[Ni(dmit)2]2·CH3CN and (PO-CONH-C2H4N(CH3)3)[Pd(dmit)2]2 where PO is 2,2,5,5-Tetramethyl-3-pyrrolin-1-oxyl and dmit is 2-Thioxo-1,3-dithiol-4,5-dithiolate. The salts are not isostructural but have similar structural features in the anion and cation packing arrangements. The acceptor layers of both salts consist of tetramers, which gather to form 2D conducting layers. Magnetic susceptibility measurements indicate that the Ni salt is a Mott insulator and the Pd salt is a band insulator, which has been confirmed by band structure calculations. The cationic layers of both salts have a previously unreported polar structure, in which the cation dipoles order as ➚➘➚➘ along the acceptors stacking direction to provide dipole moments. The dipole moments of nearest neighbor cation layers are inverted in both salts, indicating no net dipole moments for the whole crystals. The magnetic network of the [Ni(dmit)2] layer of the Ni salt is two-dimensional so that the magnetic susceptibility would be expected to obey the 1D or 2D Heisenberg model that has a broad maximum around T ≈ θ. However, the magnetic susceptibility after subtraction of the contribution from the PO radical has no broad maximum. Instead, it shows Curie–Weiss behavior with C = 0.378 emu·K/mol and θ = −35.8 K. The magnetic susceptibility of the Pd salt obeys a Curie–Weiss model with C = 0.329 emu·K·mol−1 and θ = −0.88 K.

Several anthracene derivatives with stable radical substituents have been prepared and their magnetic properties have been investigated together with those of some of the dimers available by photo-dimerization reaction. While weak magnetic interactions with Curie–Weiss behavior have been observed in most derivatives prepared, antiferromagnetic behavior being based on an S–T model has been found in the spins of TEMPO-substituted N-methylcarboxyamidoanthracene derivative 1c. The magnetic property of Mn(hfac)2 complex derived from 4-amino-TEMPO-substituted 9-methylanthracene (1d) is also described.

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.

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.

Temperature–pressure phase diagram of the 2-D organic conductor, κ-(DHDA-TTP)2SbF6 (DHDA-TTP = 2-(1,3-dithiolan-2-ylidene)-5-(1,3-dithian-2-ylidene)-1,3,4,6-tetrathiapentalene) is presented. This phase diagram exhibits a pressure boundary between insulator and Fermi liquid (FL). This boundary is considered as a critical pressure of quantum fluctuation between probable charge ordering and FL ground states. In the vicinity of the specific pressure, divergence of the prefactor A in ρ = ρ0 + AT2, is observed, where ρ is the in-plane resistivity and T is the temperature. Following the similar phase diagram to κ-(MeDH-TTP)2AsF6 by Yasuzuka et al., this is the second example in the two-dimensional 1/4-filled organic conductors, showing the temperature–pressure phase diagram of quantum critical behavior. It is remarkable that this kind of divergence of A at certain critical point is rather general phenomena at least in these 1/4-filled 2-D organic conductors, in contrast to the other 1/2-filled κ-type organic conductors, which show Kanoda's phase diagram with Mott insulator and superconductor.

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.

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.

© The Japan Society for Analytical Chemistry.The title compound, (C24H20P)(FeN2O2Cl2), was prepared by adapting of literature methods. It crystallizes in the tetragonal space group P4. The structure consists of one P(C6H5)4 cation and one Fe(NO)2Cl2 anion. The anion has one ordered NO group and one ordered Cl ligand. The other two ligands are disordered, such that one half of NO and a half of Cl are located at each position.

The title compound, (CHP)(CHNOS)CuI.0.34HO, was obtained by the slow evaporation of a solvent from an acetonitrile solution containing a mixture of (PPh)N,N'-disulfobenzoquinonediimine and CuI. The structure consists of a one-dimensional metal-organic framework of the dianion and CuI. The anionic chains are surrounded by relatively large counter-cations, and are thus well isolated from each other.

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.

Three ferrocene derivatives carrying different kinds of nitroxide radicals (1–3) were prepared as dual redox compounds. All of them have distorted molecular conformations between a Cp unit of a ferrocene group and a nitroxide group and the largest dihedral angle between the units is observed in the PO derivative 3. A unique magnetic behavior with a spin gap is disclosed in the derivative 3, reflecting two-dimensional interactions between the paired spins. Each derivative has two oxidation potentials based on both ferrocene and nitroxide groups and multi-step charge–discharge processes are found for all derivatives with the first discharge capacity over 200 A h kg−1.

The high frequency (f=70 GHz) magneto-optical response of β-ET 4 [(H 3 O)M(C 2 O 4 ) 3 ].S, where M=Fe 3+ , S=C 6 H 5 CN and C 6 H 5 NO 2 , has been investigated in the temperature range 1.4 K < T < 120 K. The angle dependence of the EPR spectra and the anisotropy of the g-factors for the two materials are presented.

The title compounds containing diamagnetic Ga are superconductors. The nitrobenzene salt shows a broad metal-semiconductor transition at 160 K but becomes superconductor below 7.5 K. The Meissner volume of a powder sample at 1.8 K is estimated at 31%. The pyridine salt also has a broad upturn in resistance at 130 K, a re-entrant metallic phase below 60 K, and a resistance loss below 1.5 K. The loss vanishes with applying magnetic field, suggesting that it is also superconductor.

Transport measurements have been carried out on single crystals of the charge transfer salt β-(BEDT-TTF) 4 [(H 3 O)Ga 3+ (C 2 O 4 ) 3 ]. C 6 H 5 NO 2 , using magnetic fields of up to 33 T and temperatures down to 0.55 K. The material is found to be superconducting with T c 7.5 K and an in-plane critical field B c2 ≥ 33 T, and to exhibit Shubnikov-de Haas (SdH) oscillations. The temperature and angle dependence of the Shubnikov-de Haas oscillations and the upper critical field are reported, allowing information about the anisotropy of the upper critical field, effective mass m*, and the Fermi-surface (FS) of the material to be deduced.

Charge transfer salts with stoichiometry β″-(BEDT-TTF) [M(CO),](18-crown-6 ether)(9HO), where M= Cr, Ga or Fe and x= 2 or 3 are reported. Their structures suggest that proton migration is possible. Variable temperature resistivity measurements on the Cr salt show metallic behaviour down to 180K. Magnetic susceptibility of the Cr salt is paramagnetic down to 1.8 K. Preliminary impedance measurements suggest that the proton conductivities of the Cr and Ga salts are the order of 10 S cm at 300 K. © 2003 Elsevier Science B.V. All rights reserved.

The preparation, crystal structure and physical properties of beta-(BDA-TTP)2GaCl4 has been investigated; the salt exhibits superconductivity at 3.1 K (onset) under a hydrostatic pressure of 7.6 kbar.

A new organic acceptor, 5,10-dimethyl-5,10-dihydroboranthrene (BMBT), was prepared and its molecular structure was determined by X-ray analysis. Redox potential suggests that BMBT is a weak acceptor. A charge transfer between BMBT and TTF was confirmed by the complex formation.

The synthesis and electrochemical properties of the DHDA-TTP donor, a hybrid of 2,5-bis(1,3-dithiolan-2-ylidene)-1,3,4,6-tetrathiapentalene (BDH-TTP) and 2,5-bis(1,3-dithian-2-ylidene)-1,3,4,6-tetrathiapentalene (BDA-TTP), has been investigated, and its ability to form metallic cation-radical salts is elucidated.

Heat capacities of κ-(BEDT-TTF) 2 Cu[N(CN) 2 ]X (X= Br and Cl) and deuterated salts were measured by chopped light are calorimetry. A glass transition due to freezing of the conformation of the ethylene moiety in the BEDT TTF molecule was deteeted around 100 K at 0.24 - 16 Hz on each salt. The glass transition temperature (ca. 80 K) at daily time scale (ca. 1 mHz) we corresponds to the temperature at which the ccoling rate or annealing sigmficantly alfect the physical properties of the superconducting transition temperature and Meissner volume on κ-(BEDT-TTF) 2 Cu(N(CN) 2 ]Br and κ-(BEDT-TTF-d 8 ) 2 Cu[N(CN) 2 ]Br.

The preparation and characterization of new organic radical anions TEMPO-NHSO 3 . (tsfa) and TEMPO-OSO 3 - (tosu), which consist of the organic stable radical (TEMPO) and the anionic functional group (-NHSO 3 - or -OSO 3 - ), has been investigated. The molecular and crystal structures of bis(triphenylphosphoranylidene)ammonium.tsfa determined by X-ray analysis indicate that tsfa exists as a monovalent anion. Black powders of the TTF.tsfa and TTF.tosu salts were obtained, in each of which the donor to anion ratio is found to be 1 : 1 by elemental analysis. TTF.tsfa shows a weak antiferromagnetic interaction with C = 0.360 emu K mol -1 and θ = -0.52 K.

Two polymorphs of a chiral conductor formulated (BEDT-TTF)3NaCr(C2O4)3·CH3NO2 have been crystallised from a solution containing the racemic anion tris(oxalato)chromate(III). In the presence of (R)-(−)-carvone the electrocrystallisation of Na3Cr(C2O4)3 with BEDT-TTF and nitromethane yields two products: hexagons crystallising in the space group P212121 (I) and needles in the space group P21 (II). Single crystal electrical transport measurements show semiconducting behavior for both salts.

The λ-type BETS alloys (BETS=bis(ethylenedithio)tetrathiafulvalene), λ-BETS2FexGa1 − xCl4 exhibited an unprecedented superconductor-to-insulator (SC-I) transition around x = 0.43 at ambient pressure. The large susceptibility drop at Tc and its recovery at tsc-i clearly show this SC-I transition reflects an intrinsic property of the crystals. The anisotropic field dependence of magnetization at 2 K indicated the insulating ground state to be antiferromagnetic. λ-BET2FexGa1 − xCl4 undergoes a MI transition at x>xc1 (≈0.5), SC transition at x