Dr Scott Turner

Many molecular charge transfer salts with organo-chalcogen donors and transition-metal complex anions have been synthesised in recent years in an effort to find lattices that combine conductivity with long range magnetic order, but in most cases interaction between the donor and anion sublattices is very weak. We have approached this issue by selecting anions that contain S or Se atoms capable of forming close non-bonding contacts with the donor molecules, and which also contain aromatic rings to form π-π contacts. In this way new ferrimagnets have been synthesised and characterised, with general formula D[M(NCX)B] where D is TTF or BEDT-TTF; M = Cr, Fe; X = S, Se; B = 1,10-phenantholine, isoquinoline. We have demonstrated that cation-anion S⋯S and π⋯π contacts are necessary. © 2002 Elsevier Science B.V. All rights reserved.

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.

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.

Measurements of magneto-transport on the organic superconductor $\kappa $-(BEDT-TTF)2I3 in magnetic fields up to 23 T at 0.48 K under hydrostatic pressures up to 9 kbar are reported. In this pronounced two-dimensional (2D) electronic system strong anomalous damping effects of Shubnikov-de Haas (SdH) oscillations are observed under very specific experimental conditions. This hints to the presence of strong electron correlations, which may occur in 2D systems. SdH high pressure experiments are reported, which show, that even 9 kbar cannot suppress the above mentioned effects in $\kappa $-(BEDT-TTF)2I3. Key words. Organic superconductors, Fermi surfaces, Magneto-quantum oscillations, Hydrostatic pressure.

The new charge-transfer salt β″-(BEDT-TTF)[(HO)Cr(CO )]S, where BEDT-TTF = bis-(ethylenedithio)tetrathiafulvalene and S = CHCl has a broad metal-insulator transition at approximately 150 K. This differs from similar salts in the BEDT-TTF tris(oxalato) metalate series, notably the superconducting materials with S = PhCN and the salt with S = CHN, which has a sharp metal-insulator transition.

Two novel salts containing the anion [Ni(mnt)2 ] − (mnt = maleonitriledithiolate) have been synthesized. The counter-ions, [Fe(II)(L 1 or L 2 )2 ], are cationic complexes where L 1 and L 2 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)(L 1 )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)(L 2 )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 chiral and racemic salts β′′-(BEDT-TTF)2(S- and rac-PROXYL-CONHCH2SO3) (S-2 and rac-2) are almost isomorphous apart from a deviation in the C–H bond direction at the chiral centre. Both salts are metallic at room temperature, with similar broad metal-insulator transitions. Band structure calculations of the chiral and racemic salts indicate that both electronic structures are quite similar. However, at 30 K, S-2 has a resistivity that is nearly three orders of magnitude higher than that of rac-2. The results suggest a significant effect of the broken inversion symmetry, due to the positional change of only one atom.

A two-dimensional (2D) organic conductor β″-(BEDT-TTF)₂ClC₂H₄SO₃ (1) crystallized in the P2₁/m and has a polar anion located on the mirror plane, parallel to the 2D BEDT-TTF conducting layer. A temperature-induced phase transition tilts the anion such that a component of its electric dipole becomes perpendicular to the conducting plane. This low-temperature phase β″-β′′-(BEDT-TTF)₂ClC₂H₄SO₃ (1L) has two crystallographically independent donor layers, A and B, each of which is bordered by the positive or negative side of the anion's dipole (← B → A ← B → A ←). This exposes each donor layer to different effective electric fields and leads to layers of A and B with dissimilar oxidation states. Consequently, the transition can be called the temperature-induced non-doped-to-doped transition. The low-temperature phase (1L) is isomorphous with β″-β′′-(BEDT-TTF)₂BrC₂H₄SO₃ (2) from room temperature to at least 100 K, suggesting that 2 is also doped and it shows a very broad MI transition at 70 K. Applying only 2 kbar of static pressure sharpens the MI transition, indicating that the tilted anion straightens, and therefore, we suggest that it can be termed a pressure-induced doped-to-non-doped transition.

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 synthesis of a novel amide-functionalised 2,6-bis(pyrazol-1-yl)pyridine-4-carboxamide ligand (bppCONH2) is described. The complex salts [Fe(bppCONH2)2](BF4)2 and [Fe(bppCONH2)2](ClO4)2 were synthesised and characterised by SQUID magnetometry, differential scanning calorimetry, variable temperature Raman spectroscopy and single crystal X-ray diffraction. DSC measurements of [Fe(bppCONH2)2](BF4)2 indicate a spin-crossover (SCO) transition with T↑ at 481 K and T↓ at 461 K, showing a 20 K hysteresis. DSC for the perchlorate salt shows an SCO transition with T↑ at 459 K and T↓ at 445 K with a 14 K hysteresis. For the BF4− salt analysis of low and high-spin state crystal structures at 101, 290 and 500 K, suggest stabilisation of the low spin state due to the formation of 1D hydrogen-bonded cationic chains. Variable temperature Raman studies of the BF4 salt support the presence of a high temperature SCO. It is speculated that the presence of hysteresis may be attributed to differences in the inter-molecular hydrogen bonding in the low spin and high spin states.

A purely-organic magnetic charge-transfer salt, δ¤-(BEDT-TTF) 2 (PO-CONHCH(cyclopropyl)SO 3)¢1.7H 2 O, has been prepared. Conducting layers consist of BEDT-TTF tetramers, in which two holes are localized, which obeys a Singlet-Triplet model. The similarity between the semiconductor-to-semiconductor transition temperature and the temperature where triplet excitation becomes negligible, suggesting that the conductions of spin singlet and triplet states become dominant in the lower and higher temperatures, respectively.

A Curie–Weiss-type paramagnetic δ′-(BEDT-TTF)₂ClC₂H₄SO₃·H₂O with θ/2 = j = −45.4 K has a phase transition at 160 K, below which the salt has a δ′-type 2D donor arrangement with 1D Heisenberg antiferromagnetic behavior with j = −121.6 K. Further cooling below 140 K induces a weak dimerization in the donor layers leading to a spin ladder system.

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.

Three new charge transfer salts of tetrathiafulvalene (TTF)-based donors with selenocyanate-metal complex anions have been synthesized. The salts have been characterized as BEDT-TTF[Cr(NCSe)]·CHCl , II, TTF[Cr(NCSe)phen], III and BEDT-TTF[Cr(NCSe)phen]·CHCl , IV, where phen = 1,10′-phenanthroline and BEDT-TTF = bis(ethylenedithio)tetrathiafulvalene. At 120 K, II crystallizes in the P2/m space group with a = 10.454(1), b = 31.990(1), c = 12.339(1) Å, β = 113.163(2)°, V = 3793.8 Å, Z = 4 and at 240 K in the same space group with a = 10.530(1), b = 32.122(1), c = 12.396(1) Å, β = 113.186(3)°, V = 3854.2 Å, Z = 4. At 240 K III crystallizes in the C2/c space group, a = 38.9272(5), b = 11.2992(1), c = 15.2540(3) Å, β = 106.8877(6)°, V = 6420.1 Å, Z = 8. The structure of IV has been solved in the P1̄ space group with a = 8.7629(3), b = 11.7977(4), c = 26.6031(9), α = 81.697(2), β = 87.858(3), γ = 74.8471(14), V = 2626.8 Å, Z = 2. All of the salts have numerous S⋯Se close atomic contacts between donors and acceptors but there is no magnetic exchange between ions, as previously seen in closely related salts such as TTF[Cr(NCS)phen] and (donor)[M(NCS)(isoquinoline)], where M = Cr, Fe and donor = TTF, BEDT-TTF or TMTTF (tetramethyltetrathiafulvalene). Indeed, II and IV are paramagnetic semiconductors whereas IlI is a paramagnetic insulator. The absence of long-range magnetic order is discussed in terms of structure-function relations since there are no π-stacking interactions between donor and acceptor, which are seen in all of the bulk magnets of this type where the donor spin is magnetically coupled to the anion. The synthesis and crystal structure of the starting material, [(CH)N][Cr(NCSe) ], I, is also reported; it crystallizes in the P1̄ space group with a = 12.220(1), b = 12.814(1), c = 13.008(1) Å, α = 99.608(6), β = 114.028(5), γ = 92.637(6)°, V = 1819.5 Å, Z = 2. © 2002 Elsevier Science (USA).

Three new charge-transfer salts of tetrathiafulvalene (TTF)-based donors with thiocyanato- or selenocyanato-metal complex anions have been synthesised. The salts isolated were [BMDT-TTF][Cr(NCS)] (1), [TM-TTF][Cr(NCS)]·2CHCN (2) and [TM-TTF][Cr(NCSe)]·2CHCN (3) [BMDT-TTF = bis-(methylenedithio)tetrathiafulvalene and TM-TTF = tetramethyltetrathiafulvalene]. Single crystals of compound 1 crystallise in the monoclinic C2/c space group with a = 37.286(3), b= 10.0539(6), c= 21.069(2) Å, β = 124.348(4)°, V = 6520.9(9) Å and Z = 4. Compound 3 was also suitable for an X-ray diffraction study, however the anionic part, [Cr(NCSe)] was highly disordered and the best solution gave a final R factor of 16.4%. A solution was found for the monoclinic space groupo C2/m with a = 113.787(3), b= 19.507(3), c = 14.735(5) Å, β = 102.90(3)°, V = 3862.9(17) Å and Z = 2. For compound 1 there are several S ⋯ S close atomic contacts between the donors and acceptors, but there is no discernible magnetic exchange between ions. Such an interaction was previously observed in related salts such as [TTF][Cr(NCS)(phenanthroline)] and [donor] [M(NCS)(isoquinoline)] [M = Cr, Fe and donor = TTF, BEDT-TTF or TM-TTF (tetramethyltetrathiafulvalene)]. Compounds 1 to 3 are all paramagnetic semiconductors in which the magnetic susceptibility is dominated by the Cr-containing anions. The structure-function relationship, along with a comparison with related compounds, indicates that there is no long-range magnetic order because there are no π-stacking interactions between donor and acceptor; these types of interactions are seen in all of the bulk magnets of this type in which the donor spin is magnetically coupled to the anion. © Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.

A novel one-dimensional copper(II)-radical complex [Cu(NITmPy)(N)(CHOH)] [NITmPy = 2-(3′-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide] has been synthesized and structurally characterized. The structure consists of neutral chains of copper(II) ions alternatively bridged by double symmetric end-on and asymmetric end-to-end azide groups. The NITmPy radical ligand coordinates to the copper(II) ions through the nitrogen atom of the pyridyl ring. The magnetic properties were investigated in the temperature range 5-300 K. The complex exhibits ferromagnetic interactions between the copper(II) ions through the end-on and end-to-end azido bridging ligands, and between the copper(II) ion and NITmPy radical. The magnetic behavior is discussed with reference to the crystal structure.

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.

Two new charge transfer salts of BEDT-TTF, bis (ethylenedithio) tetrathiafulvalene, with thiocyanato-metal complex anions have been synthesized and characterized as (BEDT-TTF)[Fe(NCS)]·CHCl and (BEDT-TTF)[Cr(NCS) (bipym)]·0.15HO, where bipym=2,2′-bipyrimidine. The Fe salt, I, crystallizes in the P-1 (No. 2) space group at 150 K with a=10.629(1) Å, b=12.099(1) Å, c=16.062(2) Å, α=99.61(1)°, β=90.87(1)°, γ=112.92(1)°, and V=1868.5(6) Å. At 150 K the Cr salt, II, crystallizes in the P-1 (No. 2) space group with a=9.243(2), b=11.781(2), c=22.925(5) Å, α=93.76(3), β=101.51(3), γ=105.45(3)°, V=2339.0(8) Å, and Z=2. Both salts exhibit close S···S contacts between the anion and cation components and in II there is no π-stacking between the bipym group and the BEDT-TTF molecules. Both salts are paramagnetic with C=4.926 I and C=1.819 II with small negative Weiss constants of -0.19 and -0.26, respectively. Therefore, the S···S contacts alone do not promote correlated magnetic effects as seen in other thiocyanato salts that also contain π-stacking. Each compound is a semiconductor and has two crystallographically independent BEDT-TTF molecules for which bond length analysis give charges of +0.9±0.1/+0.6±0.1 for I and +0.3±0.1/+0.9±0.1 for II. © 2001 Academic Press.

In 2022, we reported that the β″-(BEDT-TTF)2ClC2H4SO3 salt (1) has a phase transition at 210 K on cooling and 260 K on heating, which was suggested as a nondoped-to-doped transition. During the synthesis of 1, a second salt was coproduced, the structure and properties of which are reported here. The new salt β″-β″-(BEDT-TTF)2ClC2H4SO3 (2) has the same composition and is isomorphous to 1L, the low-temperature phase of 1. However, the salt shows no phase transition. 1H, the high-temperature phase of 1, displays rotational disorders of the −SO3– groups. In contrast, the anions in 2 have no rotational disorders but have orientational disorders. Approximately 13% of the anions in 2 have their orientation as opposed to the remaining anions. The geometrically calculated shortest O···O distance is 2.24 Å if neighbor −SO3– groups are able to rotate freely. This is 1.1 Å shorter than the sum of the van der Waals radii, and therefore, this is too close to allow free rotation. Therefore, it is proposed that 2 has no rotational disorder, which leads to no phase transition as is observed in 1.

Normal state conductivity and superconductivity together with bulk magnetic susceptibility and magnetization measurements have been measured for two molecular charge-transfer salts: beta' '-(ET)4[(H3O)Ga(C2O4)3]G (ET = bis(ethylenedithio)tetrathiafulvalene, G = pyridine for compound I and nitrobenzene for compound II). With the exception of the included guest molecules (G) the crystal structures are almost identical. Both show minima in their electrical transport at 130 K for I and at 160 K for II, but at lower temperatures their behaviors differ markedly. The resistance of I reaches a maximum at 50 K with a further small peak at 2 K and possible superconductivity only below 2 K, whereas that of II increases continuously down to 7.5 K, where an abrupt transition to a superconducting state occurs.

We have prepared an organic magnetic anion, PROXYL-4-CONHCH SO (1). The electrocrystallisation of BEDT-TTF with PPh 1 gave the first purely organic paramagnetic metal, β″-(BEDT-TTF) (1). The salt shows a broad metal-insulator transition at approximately 210 K. © The Royal Society of Chemistry 2008.

Two Fe(ii) coordination polymers formed from isomeric ligands give a diamond-like 3D network exhibiting a gradual SCO and a 2D hard magnet with a large coercive field.

New bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF)-, bis(ethylenediseleno)tetrathiafulvalene (BEST)- and bis(ethylenedithio)tetraselenafulvalene (BETS)-based organic charge-transfer (CT) salts-alpha-(BEDT-TTF)(3)(HOC2H4SO3)(2)(1), beta-(BEST)(3)(HOC2H4SO3)(2)center dot H2O (2) and alpha-(BETS)(2)(HOC2H4SO3)center dot H2O (3)-have been prepared. Salts1and2show semiconducting behaviour. Salt3, which is almost isostructural to alpha-(BETS)(2)I-3, shows metallic behaviour down to 70 K and then shows a broader metal-insulator transition than that of alpha-(BETS)(2)I-3. 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's charge-ordered and anion's disordered states.

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.

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.

This research was partially funded by JSPS KAKENHI, grant number 17K05751.

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.

SQUID magnetometry and transport measurements combined with crystal structure refinement have been used to examine the variation in superconducting properties (T and Meissner fraction) in the molecular superconductor β″-(BEDT-TTF)[(HO)Fe(CO )]·CHCN on replacing the CHCN guest molecule with pyridine (CH N). Up to approximately 65% pyridine substitution there is only a small decrease in T and Meissner fraction but above that the superconductivity is suppressed. © The Royal Society of Chemistry 2007.

The millimeter-wave response of the novel organic superconductors was studied. The magneto-optical response of the two samples containing Fe ions and the host solvents benzonitrile and nitrobenzene. The angle dependence of the electron paramagnetic resonance (EPR) spectra and the anisotropy of the g-factors for the two materials were presented. The angle of dependence of the absorption spectra at 1.4 K for the two samples were compared.

The complexes FeL(2) [L = bidentate Schiff base ligands obtained from (R)-(+)-α-phenylethanamine and 4-substituted salicylaldehydes, substituent R = H, (t)Bu, NO(2), OMe, CN, OH] react with ditopic proligands 1,4-pyrazine (pz) or 4,4'-bipyridine (bpy), to give a family of optically pure Fe(II) polymeric chain complexes of formula {FeL(2)(μ-pz)}(∞) and {FeL(2)(μ-bpy)}(∞). Crystallographic studies show that a range of structures are formed including unidirectional and bidirectional linear polymers and canted zigzag chains. Interchain interactions via π-contacts and hydrogen bonding are also observed. SQuID magnetometry studies on all of the complexes reveal antiferromagnetic interactions, the magnitudes of which are rationalized on the basis of substituent electronic properties and bridging ligand identity. For complexes with bridging pz, the antiferromangnetic interaction is enhanced by electron-releasing substituents on the Fe units, and this is accompanied by a contraction in the intrachain distance. For complexes bridged with the longer bpy the intrachain antiferromagnetic couplings are much weaker as a result of the longer intrachain distance. The magnetic data for this series of chain complexes follow a Bonner-Fisher 1D chain model, alongside a zero field splitting (ZFS) model for Fe(II) (S = 2) as appropriate. The intrachain antiferromagnetic coupling J values, g-factors, and the axial ZFS parameter D were obtained.

A series of new charge transfer salts of electron donors based on tetrathiafulvalene, TTF, with the anion [Cr(NCS)4(phen)]~ (phen = 1,10-phenanthroline) have been prepared. Single crystal X-ray diffraction provided structures for salts with donors TTF, TMTTF, tetramethyltetrathiafulvalene, and TMTSF, tetramethyltetraselenafulvalene. The salts were found to be [TTF][Cr(NCS)(phen)] at 293 K, [TMTTF][Cr(NCS)(phen)]-CHCl2 at 250 K and rrMTSF][Cr(NCS)(phen)]2-0.5CHCl at 293 K. For the TMTSF compound the solvent is disordered at 293 K so the structure was also solved at 120 K when the solvent becomes ordered. All of the salts have multiple S ⋯S or S ⋯Se close contacts between the anions and cations. The TTF salt is a bulk ferrimagnet with Tc = 9 K and is an insulator whereas the TMTTF salt is an antiferromagnetic (TN = 3.0 K) insulator. Both have close atomic interactions of the phen-donor n-stacking type, but the TMTTF salt also contains close anion-anion contacts and dimerised cations whereas the TTF salt consists of stacks of alternating cations and anions. The TMTSF salt is a paramagnetic semiconductor and does not display n stacking but has close inter-donor Se ⋯Se contacts and isolated anions which afford the magnetic and transport properties. © The Royal Society of Chemistry 2000.

A new organic-inorganic hybrid salt [TM-TTF][Cr(NCS) (isoquinoline)] (1) (TM-TTF = Tetramethyltetrathiafulvalene) has been synthesized. Compound 1 crystallizes in the triclinic P1 space group with a = 8.269(1), b = 10.211(2), and c = 11.176(2) Å, α = 89.244(9), β = 88.114(6), and γ = 74.277(7)°, V = 907.6(3) Å, and Z = 1. The crystal structure was resolved in the temperature range between 223 and 123 K, showing that changes in the crystal structure at low temperature result in stronger interactions between anions and cations. The packing of 1 consists of mixed anion-cation layers in the bc plane containing S···S and π-π anion-cation interactions, the layers being connected by very short S···S contacts between anions and cations. Magnetic measurements in a small external field show bulk spontaneous magnetization with a T of 6.6 K consistent with the presence of weakly coupled ferrimagnetic order in compound 1. The EPR measurements also demonstrate the interaction between the d and π electrons and the presence of an internal magnetic field brought about by the magnetic ordering.

Three conducting BEDT-TTF charge-transfer salts with tri-s(oxalato) metallate anions have unit cells containing both α and β″ donor packing motifs.

Our group has recently focused on obtaining new molecular magnets based on radical BEDT-TTF or TTF derivatives. In these series, the aim is to combine the magnetic and conducting properties in the same material via the radical donor. We report here the structural and the physical properties of three salts with donors TTF (ferrimagnetic insulator), TMTTF (antiferromagnetic insulator) and TMTSF (paramagnetic semiconductor), containing the Reinekes anion derivative [Cr(NCS)4(phenanthroline)]. The role of the crystal packing in determining the physical properties is discussed.

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. © 2006 Elsevier Ltd. All rights reserved.

We applied magneto-optical techniques to investigate the electron spin resonance (ESR) spectra of single crystal and powder samples of the organic superconductor β″-(BEDT- TTF)4[(H3O)Fe (C 2O4]C6H5CN. Data were obtained in magnetic fields up to 10 Tesla using both cylindrical and rectangular resonators at 55, 63 and 72 GHz and transmission measurements at 95 and 190 GHz with field modulation. Analysis of the high field-high frequency ESR lines for different field orientations and temperatures allows the determination of the g-value anisotropy and the zero-field splitting parameters for the Fe3+ ions (S = 5/2), showing that they occupy a site with distorted octahedral symmetry. The temperature and frequency dependences of the magneto-optical spectra are used to identify the nature of the interaction between localised Fe spins and between the local moments and the delocalised carriers. © EDP Sciences,.

Short synthetic routes to racemic derivatives of bis(ethylenedithio)tetrathiafulvalene carrying one hydroxymethyl (HMET), alkoxymethyl or dialkoxymethyl side chain are reported along with cyclic voltammetry measurements and conversion of HMET to (2:1) radical cation salts. © 2001 Elsevier Science Ltd.

© 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.

In recent years, concern has been raised about the charge fluctuation of the superconducting transition in the loosely dimerized molecular conductors. Not only the observation of the charge fluctuation is of considerably important but also the understanding of the mechanism of the fluctuation. We have observed degree of charge fluctuation of several β''-type ET salts. The β''-type ET salt is one of the best model compounds because the direction of the largest inter-site Coulomb interaction is perpendicular to that of the largest transfer integral. This structural property allows us to examine the role of inter-site Coulomb interaction from the viewpoint of the inter-molecular distance. The difference in the molecular charges between the charge rich site and the charge poor sites, Δρ, is correlated with the conducting behavior; the superconducting materials have the small but finite Δρ, whereas Δρ of the insulating (metallic) materials is large (almost zero). After the analysis of the configuration in the inter-molecular distances, we have found that the degree of fluctuation, Δρ, is attributed to the number of the most stable charge distribution(s), NS, and the number of the energy levels of the allowed charge distribution, NA. The superconducting materials belong to the condition of N ≥2 and N ge;2. Indeed, this condition contributes to the fluctuation of the molecular charges. © 2010 Elsevier B.V. All rights reserved.

The preparation, crystal structures and properties of three new BEDT-TTF, bis(ethylenedithio)tetrathiafulvalene, (ET for short), charge transfer salts β″(ET).[(HO)Cr(C O)].CHNOI, β″(ET).[(HO)Fe(C O)].CHNO II and (ET).[Fe(CO)] III are reported. The structures of I and II consist of alternating layers of ET and an approximately hexagonal network formed by HO and the metal with the solvent molecule, CHNO, occupying hexagonal cavities in the anion layer. Both CHNO salts are superconducting, the iron salt having a T of 6.2 K and the chromium salt having a T of 5.8 K. The structure of (ET)[Fe(CO)] consists of an iron oxalate bridged dimer, (Fe-Fe distance 5.472 Å), interspersed with ET in a "checker board" arrangement. It is monoclinic and crystallises in the P2/n space group. At 150 K a = 16.8068 (3) Å, b = 10.9556 (2) Å, c = 19.4109 (3) Å, β = 102.1593 (9)° and V = 3493.92 (10) Å. Squid measurements show short range antiferromagnetic ordering.

The electrically conducting salt -(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.

The results of x-ray fluorescence measurements of the molecular superconductors (ET)[(HO)Fe(CO) ]·CHCN (T = 8.5 K) and (ET)[(HO)Cr(CO) ]·CHCN (T ∼ 6 K) and molecular conductor (ET)[(HO)Fe(CO) ]·CHN containing paramagnetic 3d ions are presented. The following transition of the x-ray emission valence spectra are monitored: C K α, N K α (2p→1s transition) and Fe L, Cr L (3d4s→2p transition). It is found that the electronic structure of the solvents (benzonitrile, pyridine) that occupy the hexagonal cavities formed by the anionic layer is close to that of the neutral molecule. The ratio of the emission intensities of the peaks L to L for Fe and Cr is found to be 2.8-3.1 times higher for (ET)[(HO)Fe(CO) ]·CHCN and (ET)[(HO)Cr(CO) ]·CHCN than for pure metals. This indicates that the paramagnetic 3d ions are situated in highly insulating anionic layers. We did not find any changes in the C K α emission for different solvent molecules.

We report high-field magnetotransport measurements on β″ -(BEDT-TTF)[(HO)M(CO) ]Y, where M =Ga, Cr, and Fe and Y=CHN. We observe similar Shubnikov-de Haas oscillations in all compounds, attributable to four quasi-two-dimensional Fermi-surface pockets, the largest of which corresponds to a cross-sectional area ≈8.5% of the Brillouin zone. The cross-sectional areas of the pockets are in agreement with the expectations for a compensated semimetal, and the corresponding effective masses are ∼m , rather small compared to those of other BEDT-TTF salts. Apart from the case of the smallest Fermi-surface pocket, varying the M ion seems to have little effect on the overall Fermi-surface topology or on the effective masses. Despite the fact that all samples show quantum oscillations at low temperatures, indicative of Fermi liquid behavior, the sample and temperature dependence of the interlayer resistivity suggest that these systems are intrinsically inhomogeneous. It is thought that intrinsic tendency to disorder in the anions and/or the ethylene groups of the BEDT-TTF molecules leads to the coexistence of insulating and metallic states at low temperatures. A notional phase diagram is given for the general family of β″-(BEDT-TTF) [(HO)M(CO)]Y salts.

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.

We report the first molecular charge transfer salt containing channels of H O /H O within its lattice; it is formulated β″-(BEDT-TTF) [(H O)Cr(C O ) ] [(H O) (18-crown-6)]·5H O [BEDT-TTF = bis(ethylenedithio)tetrathiafulvalene], deduced from the crystal structure and C=C and C-S bond lengths and Raman stretching frequencies.

We have prepared new organic anionic acceptors Br(2)XQNHCH(2)SO(3)(-) (2 X=Br 3 X=BryCl1-y (y approximate to 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 beta-(ET)(5)(AA)(2) DCE zH(2)O and -(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 (C) 2009 Elsevier B V All rights reserved

Three new charge transfer salts of BEDT-TTF and TTF with the counter ions [M(NCS)4(C9H7N)J~ (M = Cr, Fe; C9H7N = isoquinoline) are described. The materials are prepared by standard electrocrystallisation techniques. The nature of the anion is verified in the crystal structure of the salt [C9H8N][Cr(NCS)4(C9H7N)]-C,2H24O6-H2O which is used as the electrolyte when M = Cr. All of the charge transfer salts display long range ferrimagnetic order originating from the interaction between M (5=3/2 or 5= 5/2) and the donor (5= 1/2). The measured critical temperatures are 4.2 K (BEDT-TTF, M = Cr), 4.5 K (BEDT-TTF, M = Fe) and 8.9 K (TTF, M = Cr). Each of the compounds also shows a modest magnetic hysteresis of 338, 18 and 75 Oe for BEDT-TTF salts of M = Cr, Fe and the TTF salt of Cr, respectively. © The Royal Society of Chemistry 2000.

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.

We report high-field magnetotransport measurements on β″-BEDT- TTF[(HO)M(CO)]C HN, where M=Ga, Cr or Fe . In spite of the differing M ions, these compounds have very similar Fermi surfaces. We observe four distinct Shubnikov-de Haas frequencies, corresponding to four Fermi-surface pockets; the frequencies exhibit the additive relationship expected for a compensated semimetal. The compounds show paramagnetic behaviour and no superconductivity down to 0.5 K, in contrast to other materials of the same family with different solvent molecules. © 2003 Elsevier B.V. All rights reserved.

At 270 K, the charge transfer salt(TTF)[Mo(CN)]·4H O,I, crystallizes in the triclinic space group P1̄ with a = 9.9094(2), b = 10.6781(2), c = 23.6086(7) Å, a = 75.7910(8), β = 88.6010(9), γ = 78.5250(8)°, V = 2372.5(1) Å and Z = 2. At 120 K, the space group is unchanged with a = 9.7990(7), b = 10.6630(5), c = 22.9940(2) Å, a = 79.981(4), β = 89.798(4), γ = 79.013(4)°, V = 2321.5 Å and Z = 2. On comparing the two sets of data, we see significant changes in the cell parameters, most notably in the angle a. Variable temperature crystallographic studies indicate a first order phase transition accompanied by hysteresis, which corresponds to a change in the transport properties.I is a semiconductor and the high temperature activation energy of 0.06 eV changes sharply to 0.15 eV below 236 K. Bulk magnetic susceptibility and ESR measurements indicate that the TTF molecules are antiferromagnetically coupled. The temperature dependence of the EPR spectrum changes from 300-200 K, in approximate agreement with the transport and structural results. The optical spectrum of (TTF)[Mo(CN)]·4HO consists of several broad bands assigned to TTF charged molecules, to [Mo(CN)] and to charge transfer from the donors to the acceptor in the near infra-red range. Preliminary magnetic susceptibility measurements under light irradiation with a multi-line (752.5-799.3 nm) laser were also performed, but no photomagnetic effect was noted.

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.

Long-range ferrimagnetic order in which one magnetic sub-lattice is formed from partly-occupied p-orbitals and the other from d-orbitals can be achieved in molecular ion-radical salts where the cations are oxidised organo-chalcogen donors and the anions are 3d-metal complexes containing both N-bonded NCS and planar N-heterocyclic ligands. Overlaps between p-orbitals of the radical cations and those of the heterocycle are implicated in the cation-anion exchange pathway.

We report high-field magnetotransport measurements on β″-(BEDT- TTF)4[(H3O)M(C2O4) 3]· solvent, where M=Ga3+, Cr3+ and Fe3+ and solvent=C5H5N. 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 meff ≈ 0.5-1.1 me whereas the Dingle temperatures varies between TD ≈ 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. © EDP Sciences.

This paper reports the preparation, X-ray crystal structure, conducting and magnetic properties of α-(BEDT-TTF)]Fe(phen) (NCS)[ (1) [BEDT-TTF = bis(ethylenedithio)tetrathiafulvalene, phen = 1,10-phenanthroline] together with the crystal structure of (BEDT-TTF)]Cr (isoq)(NCS)[ (2) (isoq = isoquinoline) for which the physical properties have been reported previously. Compound 1 crystallizes in the triclinic space group P1 (no. 2), a = 12.1528(1), b = 16.8269(3), c = 27.0703(4) Å, α = 95.726(1), β = 95.834(1), γ = 108.080(1)°, Z = 4, R = 0.0610 for 9764 reflections with I > 2σ(I); 2 crystallizes in the monoclinic space group P2/c (no. 14), a =10.623(5), b = 14.656(8), c = 12.701(7) Å, β = 100.19(2)°, Z = 2, R = 0.0737 for 2747 reflections with I > 2σ(I). The magnetic and transport properties have shown that compound 1 is a paramagnetic semiconductor with σ = 2.2 × 10 Ω cm. © 2002 The Royal Society of Chemistry.

We report magnetotransport measurements on the quasi-two-dimensional charge-transfer salts β″-(BEDT-TTF)4[(H3O)M(C2O4)3]Y, with Y=C6H5NO2 and C6H5CN using magnetic fields of up to 45 T and temperatures down to 0.5 K. A surprisingly robust superconducting state with an in-plane upper critical field Bc2 33T, comparable to the highest critical field of any BEDT-TTF superconductor, and critical temperature Tcâ 7K is observed when M=Ga and Y=C6H5NO2. The presence of magnetic M ions reduces the in-plane upper critical field to 18T for M=Cr and Y=C6H5NO2 and M=Fe and Y=C6H5CN. Prominent Shubnikov-de Haas oscillations are observed at low temperatures and high magnetic fields, showing that the superconducting salts possess Fermi surfaces with one or two small quasi-two-dimensional pockets, their total area comprising 6% of the room-temperature Brillouin zone; the quasiparticle effective masses were found to be enhanced when the ion M was magnetic (Fe or Cr). The low effective masses and quasiparticle densities, and the systematic variation of the properties of the β″-(BEDT-TTF)4[(H3O)M(C2O4)3]Y salts with unit-cell volume points to the possibility of a superconducting groundstate with a charge-fluctuation-mediated superconductivity mechanism such as that proposed by Merino and McKenzie [Phys. Rev. Lett. 87, 237002 (2001)], rather than the spin-fluctuation mechanism appropriate for the κ-(BEDT-TTF)2X salts. © 2005 The American Physical Society.

2,6-Bis(pyrazol-1-yl)pyridine (L1) and 2,2:6′,2″-terpyridine (L2) are popular ligands for use in a wide range of applications in coordination chemistry. Both ligands are capable of forming metal complexes with highly interesting and potentially exploitable properties: luminescence, catalytic redox activity and magnetic spin crossover (SCO). SCO materials have received attention because of the potential for incorporation into commercially relevant technologies such as sensors and information storage media. This review explores the potential of ‘back to back’ L1 SCO polymers using reported examples, and looks towards the larger L2 chemical library, covering the coordination chemistry with a focus on magnetic properties. In principle, polymeric coordination materials are easier to process and may offer an easier route to tuning properties that are dependent on the electronic environment. It is the intention of this review to highlight the potential of these materials, with the goal of promoting the development of multifunctional SCO hybrids.

A novel ferrocene-containing dianion, Fe(C H - CH(CH )NHCOCH SO ) (1), has been prepared. The oxidation potential of the PPh 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. © 2012 Elsevier B.V. All rights reserved.