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Co(ii)–N4 complex displays slow magnetisation at zero static field, exhibiting a high spin-reversal energy barrier Ueff = 85 cm−1.

Spin-ladders are quantum magnetic systems at the crossroads between one and two dimensions that have attracted increasing interest during the last decades due to unique properties critically dependent on spin system topology. The first materials where spin-ladder behaviour was identified were transition metal oxides and copper(II) halides or coordination polymers. However, since the report of the first spin-ladder based in an organic molecule in 1997, an increasing number of molecular compounds showing spin-ladder behaviour have been reported. Their structural and magnetic properties are reviewed with emphasis on the possibilities offered by molecular units of different nature and crystal engineering tools to develop new spin-ladder systems.

Methyl-ethylenedithio-tetrathiafulvalene (Me-EDT-TTF (1) and dimethyl-ethylenedithio-tetrathiafulvalene (DM-EDT-TTF (2) are valuable precursors for chiral molecular conductors, which are generally obtained by electrocrystallization in the presence of various counter-ions. The number of the stereogenic centers, their relative location on the molecule, the nature of the counter-ion and the electrocrystallization conditions play a paramount role in the crystal structures and conducting properties of the resulting materials. Here, we report the preparation and detailed structural characterization of the following series of radical cation salts: (i) mixed valence (1)2AsF6 as racemic, and (S) and (R) enantiomers; (ii) [(S)-1]AsF6·C4H8O and [(R)-1]AsF6·C4H8O where a strong dimerization of the donors is observed; (iii) (1)I3 and (2)I3 as racemic and enantiopure forms and (iv) [(meso)-2]PF6 and [(meso)-2]XO4 (X = Cl, Re), based on the new donor (meso)-2. In the latter, the two methyl substituents necessarily adopt axial and equatorial conformations, thus leading to a completely different packing of the donors when compared to the chiral form (S,S)/(R,R) of 2 in its radical cation salts. Single crystal resistivity measurements, complemented by thermoelectric power measurements in the case of (1)2AsF6, suggest quasi-metallic conductivity for the latter in the high temperature regime, with σRT ≈ 1–10 S cm–1, while semiconducting behavior is observed for the (meso)-2 based salts.

The synthesis and characterisation of three metal bisdithiolene complexes based on the recently reported highly extended ligand incorporating fused tetrathiafulvalene and pyrazine moieties, [M(pztdt)2], M = Ni, Pd, Pt and pztdt = pyrazinetetrathiafulvalenedithiolate, are reported. These complexes were obtained under anaerobic conditions as crystals of dianionic tetrabutylammonium salts. The crystal structures of Ni and Pd complexes as determined by single crystal X-ray diffraction confirm the ability of these molecules to established interactions with their neighbours through the pyrazine moieties. These dianionic complexes easily undergo oxidations to their monoanionic and neutral states, with a narrow range of stability for the monoanionic and an extended one for the neutral forms that is rather insoluble in common solvents.

An electrochemical study of the dimerisation of the [Fe(qdt) 2 ] 2 2− and [Fe(mnt) 2 ] 2 2− iron complexes in dichloromethane, dimethylformamide and acetonitrile, by cyclic voltammetry and ionic conductivity is reported. Ionic conductivity measurements indicate an increased dissociation of the dimers in dimethylformamide and acetonitrile compared to dichloromethane. In [Fe(mnt) 2 ] in dichloromethane, only dimer oxidation processes are observed in cyclic voltammetry, while in [Fe(qdt) 2 ] both dimeric and monomeric species are involved in redox processes. In acetonitrile and DMF the observed processes correspond to the dissociated monomeric species only. This study demonstrates the major role of the nature of the solvent in the monomer/dimer equilibrium in solution, which appears more easily shifted towards dissociation in the complex with qdt ligands than with mnt and is favoured by N- and O-containing solvents.

The alpha-(Per)(2)[M(mnt)(2)] compounds with M = Pt and Au are isostructural two-chain solids that in addition to partially oxidized conducting perylene chains also contain anionic chains that can be either paramagnetic in the case of M = Pt or diamagnetic for M = Au. The electrical transport and magnetic properties of the solid solutions (Per)(2)[Pt-x-Au(1-x)(mnt)(2)] were investigated. The incorporation of paramagnetic [Pt(mnt)(2)] impurities in the diamagnetic chains, and the effect of breaking the paramagnetic chains with diamagnetic centers for the low and high Pt range of concentrations were respectively probed. In the low Pt concentration range, there is a fast decrease of the metal-to-insulator transition from 12.4 K in the pure Au compound to 9.7 K for x = 0.1 comparable to the 8.1 K in the pure Pt compound. In the range x = 0.5-0.95, only beta-phase crystals could be obtained. The spin-Peierls transition of the pure Pt compound, simultaneous with metal-to-insulator (Peierls) transition is still present for 2% of diamagnetic impurities (x = 0.98) with transition temperature barely affected. Single crystal X-ray diffraction data obtained a high-quality structural refinement of the alpha- phase of the Au and Pt compounds. The beta-phase structure was found to be composed of ordered layers with segregated donors and anion stacks, which alternate with disordered layers. The semiconducting properties of the beta-phase are due to the disorder localization effects. info:eu-repo/semantics/publishedVersion

We summarize structural instabilities exhibited by the one dimensional (1D) (arene)2X family of organic conductors in relation with their electronic and magnetic properties. With a charge transfer of one electron to each anion X these salts exhibit a quarter-filled (hole) conduction band located on the donor stacks. Compounds built with donors such as fluorenthene and perylene derivatives and anions X such PF6 or AsF6 exhibit a high temperature (TP~170K) conventional Peierls transition which is announced by a sizeable regime of 1D 2kF charge density wave fluctuations (kF is the Fermi wave vector of the 1D electron gas located on Per stacks). Surprisingly, and probably because of the presence of a multi-sheet warped Fermi surface, the Peierls transition is considerably reduced in the perylene series α-(Per)2[M(mnt)2] where X is the dithiolate molecule with M=Au, Cu, Co and Fe. A special attention is devoted in this paper to physical properties of α-(Per)2[M(mnt)2] salts which with M=Pt, Pd and Ni incorporate segregated S=1/2 1D antiferromagnetic (AF) dithiolate stacks with 1D metallic Per stacks. We analyse conjointly the structural and magnetic properties of these salts in relation with the 1D spin-Peierls (SP) instability located on the dithiolate stacks. We show that the SP instability of the Pd and Ni derivatives occurs in the classical (adiabatic limit) while the SP instability of the Pt derivative occurs in the quantum (anti-adiabatic limit). Furthermore we show that in the Pd and Ni derivatives frustrated 1st neighbour direct and 2nd neighbour indirect (through a fine tuning with the mediated 2kF RKKY coupling interaction on Per stacks) AF interactions add their contribution to the SP instability to open a singlet-triplet gap. Our analysis of the data show unambiguously that magnetic α-(Per)2[M(mnt)2] salts are a typical realization of the physics predicted for two chain 1D Kondo lattices.

A series of new [M(cbdt)2]z− complexes of the 4-cyanobenzene-1,2-dithiolate (cbdt) ligand with a range of transition metals M (M = Zn, Co, Cu, Au, Ni, Pd) were prepared in different oxidation states (z = 0, 1, 2) as salts with several cations and characterised by X-ray diffraction, cyclic voltammetry, EPR and static magnetic susceptibility. Their properties are discussed in comparison either with the Fe analogue or corresponding complexes based on the dicyano substituted ligand (dcbdt) previously described by us. These complexes can be prepared either from the ligand dithiol as previously described for the Fe analogue, or in a more convenient way to obtain the more reduced forms, from the 4-cyanobenzene-1,3-dithiole-2-thione (1) which is described here for the first time. The structure of these complexes presents square planar coordination geometry, and belong to four distinct groups: (i) the Au monoanionic compound 4a is monoclinic, C2/c, where the complex presents a cis–trans disorder; (ii) the compounds 10b, 7b of the dianionic Pd and Ni complexes, are isostructural, monoclinic, P21/c, with the metal in an inversion centre, a perfect square-planar coordination geometry and a ligand trans configuration; (iii) the compounds (8a and 9a) of the Co and Cu dianionic complexes, which are monoclinic P21, with the metal located in a general position with square planar coordination and ligand trans configuration; and (iv) the monoanionic Cu compound 12 is triclinic, P 1 ¯ , with the metal in a general position with almost ideal square-planar coordination and ligand trans configuration. These complexes present redox properties intermediate between those based on dcdbt and unsubstituted benzenedithiolate ligand (bdt), and the gold complex can be obtained in the neutral state. The EPR and static magnetic susceptibility measurements show that the dianionic cobalt and copper complexes (8a and 9a) the monoanionic nickel (3), and the neutral gold (11) complexes are paramagnetic corresponding to an S = ½ state. The powder EPR spectrum of the dianionic Co complex 8a presents a hyperfine structure typical of I = 7/2 59Co with a component a0x = 8.6 mT.

The Ni and Au bis(dithiolene) complexes based on the 1-(pyridine-4-yl)-ethylene-1,2-dithiolate ligand were prepared in their neutral state and characterized namely by single-crystal X-ray diffraction, electronic UV–Vis–NIR spectroscopy, EPR and magnetic susceptibility measurements. The crystal structure of the neutral complex [Ni(4-pedt)2] 0 lacks a regular and multidimensional extended network of short contacts and as a consequence electrical conductivity measurements in single crystals show a semiconducting behavior with room temperature values of the order of 10 6 S/cm, while the magnetic measurements of the gold compounds indicate a reduced effective magnetic moment due to strong antiferromagnetic interactions between radical neutral complex units. The nitrogen coordination ability of theses complexes was demonstrated by the coordination of pyridine to a sodium ion observed in the [Au(4-pedt)2]2NaPF6 complex which was also characterized by single-crystal X-ray diffraction and magnetization. In this compound the Na ions in half occupied positions are coordinated by anion fluorine atoms and nitrogen and carbon atoms from the neutral [Au(4-pedt)2] complexes.

The paper reports all-organic strain and stress sensitive films that use electrical monitoring approach. The films were prepared by self-metallizing polycarbonate films with the single component molecular conductor [Au(α-tpdt) 2 ] 0 (tpdt = 2,3-thiophenedithiolate). It was shown that [Au(α-tpdt) 2 ] 0 by its nature is able to form metallic solid material with low crystallinity. Electromechanical tests demonstrated that the developed films are strain-resistive materials with advanced elastic properties: their electrical resistance varies linearly with uniaxial elongation up to relative strain being of 1.0% that is about five times larger than that for conventional metals. The gauge factor of the films is 4.4 and stress sensitivity is 30 Ω/bar. The processing characteristics of polycarbonate films, self-metalized with a metallic [Au(α-tpdt) 2 ] 0 -based layer, make them potentially useful for engineering flexible, lightweight, strain and pressure sensors. Due to electromechanical characteristics these films are suited to strain sensing applications requiring miniature strain control in a wide deformation range.

The synthesis and characterization of a new extended tetrathiafulvalene (TTF) dithiolene ligand substituted with alkyl pyridine groups, pyridylethylsulfanyltetrathiafulvalenedithiolene (pesdt2−), as well as the corresponding gold (III) complex [Au(pesdt)2]− obtained as a tetrabutylammonium salt are described. The oxidation potential of this complex is rather low and the paramagnetic neutral complex is obtained as an electrically insulating microcrystalline powder.

The chemistry of transition metal dithiolene complexes based on thiophene-dithiolene ligands (TD) is reviewed, from the ligand synthesis and complex preparation to the molecular structure and solid state physical properties of different compounds based on them. The ligands considered are based mainly either on simple thiophene-dithiolates (α-tpdt = 2,3-thiophenedithiolate, dtpdt = 4,5-dihydro-2,3-thiophenedithiolate, and tpdt = 3,4-thiophenedithiolate), or in more extended and delocalised dithiolate ligands (α-tdt = 3-({5-[(2-cyanoethyl)thio]-2-thieno[2,3-d][1,3]dithiol-2-ylidene-1,3-dithiol-4-yl}thio)propanenitrile and dtdt = 3-{5-[(2-cyanoethyl)thio]-2-(5,6-dihydrothieno[2,3-d][1,3]dithiol-2-ylidene-1,3-dithiol-4-yl)thio}propanenitrile) that besides the thiophenic ring also incorporates a fused TTF moiety. Dithiolene complexes based on ligands containing appended thiophenic units will also be briefly considered. The structural variability of these complexes that in addition to the usual square planar coordination geometry, M(TD)2, can also present dimeric, [M(TD)2]2, or cluster structures such as [Cu4(TD)3] and [Ni4(TD)6], is addressed. The role of the thiophene group and its ability to enhance electronic delocalisation from the metal dithiolene core throughout the ligand and to establish solid state networks of S⋯S interactions is discussed. The importance of these complexes as useful building blocks to prepare molecular materials with very interesting magnetic and transport properties, ranging from metamagnets to Single Component Molecular Metals, is illustrated by different compounds based on them.

The chemistry of transition metal dithiolene complexes containing N coordinating groups and the corresponding TTF donors, is reviewed starting from the ligand synthesis to the coordination structures where these dithiolene complexes are used as bridging units. The dithiolene ligands containing N coordinating atoms present two coordination poles which can selectively bind different metals and act as bridging units in a variety of coordination architectures. The transition metal dithiolene complexes based on these N containing ligands and the corresponding TTF donors can be themselves regarded as ligands. These can be used to coordinate other metals, potentially leading to a diversity of hetero metallic coordination architectures. With the use of appropriate auxiliary ligands they can lead to discrete metal complexes. In addition they can lead to more extended polymeric structures of different dimensionality such as 1D chains, 2D layers or even 3D polymers can also be obtained.

Phase equilibria in the Ce–Au–Sb system were derived from X-ray diffraction data and, optionally, from scanning electron microscope analysis of annealed at 870 K alloys. The structures of compounds were investigated using X-ray single crystal and powder diffraction methods. Five ternary compounds were found to exist within the investigated concentration region (0–50 at.% Ce). New U3Cu2Sb3-type Ce3Au2Sb3 compound (a = 4.5966(4) A, c = 24.005(2) A, space group P63/mmc, no. 194) was discovered and studied by X-ray single crystal diffraction. The existence and crystal structures of following compounds were confirmed at 870 K: the ZrCuSi2-type CeAu1−xSb2, UHg2-type Ce(Au1−xSbx)2 and Y3Au3Sb4-type Ce3Au3Sb4. For the reported earlier UHg2-type Ce(Au1−xSbx)2 and ZrCuSi2-type CeAu1−xSb2 compounds the homogeneity regions were established from annealed at 870 K alloys: 0.19 ≤ x ≤ 0.28 and 0 ≤ x ≤ 0.21 respectively. At 870 K, the structure of CeAuSb compound was found to be related to the CaIn2-type from X-ray powder diffraction data. Moreover, the single crystal X-ray diffraction studies of the as-cast CeAu1−xSb2 for x = 0.118(2) and x = 0.162(4) are given in present paper as well.

The monoanionic Ni, Au and Cu bisdithiolene complexes based on the 1-(pyridin-4-yl)-ethylene-1,2-dithiolate were prepared and isolated as [PPh4]+, [n-Bu4N]+ and [Na(18C6)]+ salts which were characterised by single-crystal X-ray diffraction, cyclic voltammetry, EPR and magnetic susceptibility measurements. All the complexes adopt a square planar coordination geometry with a trans arrangement of the substituent pyridine rings whose planes are rotated from 13° to 33° relatively to the central MS4 core. The C–C and C–S bond lengths are consistent with ene-1,2-dithiolate form of the ligand and MIII oxidation state. The Ni complexes are paramagnetic with an effective magnetic moment of ∼1.7 BM.

The synthesis of the dithiol precursor of the new ligand 4-cyanobenzene-1,2-dithiolate (cbdt) is described. The (n-Bu4N)[Fe(cbdt)2] complex, was prepared and characterised by X-ray diffraction, Mossbauer spectroscopy and magnetisation measurements. The crystal structure consists in cis [Fe(cbdt)2]- units dimerised in a trans fashion, with Fe in a square pyramidal coordination, the dimers being well isolated from each other by the cations. The magnetic susceptibility shows that the [Fe(cbdt)2]− units have a S = 3/2 spin configuration.

The preparation and characterization of 5,6-substituted-1,10-phenanthrolines, phdtos = 5,6-bistosyl-1,10-phenanthroline (1) and phdbt = 5,6-dibenzyltiol-1,10-phenanthroline (2) are described. The synthesis of (1) was achieved in good yield via the corresponding dihydroxide and 2 was obtained by cross-coupling reaction of 5,6-dibromo-1,10-phenanthroline and benzylthiol mediated by a palladium catalytic system in refluxing toluene (120 °C). These phenanthroline derivatives were used as ligands to afford [FeII(phdtos)3](PF6)2 (5) and [FeII(phdbt)3](PF6)2 (6) complexes.

Millimeter size CuS single crystals with a dark indigo blue color and a plate hexagonal shape have been successfully grown by the high-temperature solution growth technique using the KCl–LiCl eutectic as solvent. Surface microtopographic studies of the crystals indicated that the growth is made by the lateral spreading of the layers. Electrical resistivity measurements clearly show an anomaly at T ∼55 K, related with the low-temperature structural transition, a high residual resistivity ratio of ∼400 and a sharp superconducting transition at T ≈1.7 K confirming the very good quality of the crystals.

Two new TTF-based donors that are dithiolene ligand precursors, 3-{5-[(2-cyanoethyl)thio]-2-(5,6-dihydrothieno[2,3-d][1,3]dithiol-2ylidene-1,3-dithiol-4-yl)thio}propanenitrile, dtdt (1) and 3-({5-[(2-cyanoethyl)thio]-2-thieno[2,3-d][1,3]dithiol-2-ylidene-1,3-dithiol-4yl)thio}propanenitrile, a-tdt (2), were synthesized and characterized. The electrochemical properties of these compounds were studied by cyclic voltammetry (CV) in acetonitrile. Compound 1 shows two reversible oxidation process at 1 E1/2 = 0.639 V and 2 E1/2 = 0.997 V versus Ag/AgCl. This same processes occurs at 1 E1/2 = 0.612 V and 2 E1/2 = 0.906 V in the case of 2. The crystal structures con

Salts of [FeIII(sal2-trien)]+and [FeII(phen)3]2+ cations and M[(dcbdt)2]− anions with M = Ni and Au (dcbdt = dicyanobenzenedithiolate) with formula [Fe(sal2-trien)] [M(dcbdt)2] and [Fe(phen)3] [M(dcbdt)2]2 were obtained and characterized by single X-ray diffraction and magnetic measurements. None of these salts shows a clear spin crossover behaviour and their magnetic properties are due essentially to the cations in a high spin S = 5/2 and low spin states for the FeIII and FeII salts respectively. The magnetic Ni sublattices in both compounds appear to have a negligible direct contribution to the magnetization but enhance the AF interactions in the cation sublattice.

Based on Rietveld refinement of X-ray powder diffraction data collected from RNi 4 B samples (R = Gd, Tb, Er) annealed at 1070 K, a CeCo 4 B structure type (space group P 6/ mmm (N191), Z = 2) was determined for all compounds.

We present the synthesis and structural characterization of the salt [Fe(bpp)2][MnCr(ox)3]2 · bpp · CH3OH. It crystallizes in the monoclinic space group. This material contains an anionic [MnCr(ox)3]− 3D 10-gon ferromagnetic network, that orders below 3.0 K. The channels created by this architecture are filled by the spin crossover cations [Fe(bpp)2]2+ (bpp = 2,6(bispyrazol-3-yl)pyridine), free ligand and solvent molecules. No spin transition has been observed at ambient pressure.

Nanowires of molecule-based charge-transfer salts are prepared using two different processing techniques. Isolated [TTF][TCNQ] nanowires are grown by a simple adsorption in organic solution method on stainless steel conversion coatings, used as substrates. They are characterized by Raman spectroscopy and current–voltage measurements. Nanowire films of Per2[Au(mnt)2] and (EDT-TTFVO)4(FeCl4)2 are electrodeposited on (001)-oriented silicon wafers, used as anodes. In the second case, growth as nanowires occurs after functionalizing the Si electrode with a phospholipidic membrane. Electrodeposited nanowire films are studied by various techniques, including electron microscopy, vibrational spectroscopies, X-ray photoelectron spectroscopy and conductivity measurements.

Electrical resistivity and specific heat of a stoichiometric NpFe 4 Al 8 polycrystalline sample were measured between 2 and 300 K, and under 0–9 T applied magnetic fields. Both measurements confirm the occurrence of magnetic ordering at 135(5) K. The electrical resistivity displays a second anomaly at 113(5) K, which was ascribed to the neptunium magnetic ordering. There is a clear evidence of predominant ferromagnetic-like interactions in this compound, but with a complex magnetic structure, as previously suggested by the magnetic measurements and theoretical calculations. The high γ = 183(10) mJ mol −1 K −2 value classifies the NpFe 4 Al 8 compound as a moderate heavy fermion.

UFe6Ga6 polycrystalline samples were prepared by arc-melting, and single crystals were grown by the Czochralski method. This compound crystallizes in the orthorhombic ScFe6Ga6-type structure (space group Immm, a=5.0560(4), b=8.5484(7) and c=8.6914(7) A), an ordered variant of the ThMn12-type structure. A ferromagnetic-type transition at TC=530(5) K is seen in the magnetization and A.C.-susceptibility measurements, and no other magnetic anomaly is observed down to 5 K. Single crystal magnetization measurements along the three different crystallographic axes indicated a as the easy direction, with a spontaneous magnetization MS=12.3 μB/f.u. at 5 K. The analysis of the 57Fe Mossbauer spectroscopy data indicated magnetic hyperfine fields, Bhf, significantly lower on 4f sites than on 8k sites, in agreement with the trend already observed on UFexAl12−x, where the average Bhf were found to increase with the iron–iron interatomic distances.

The new compound, (bedt-ttf)[Au(cdc)2], where bedt-ttf stands for bis(3,4;3′,4′-ethylenedithio)2,2′,5,5′-tetrathiafulvalene(+) and cdc for cyanoimidodithiocarbonate(2−), was synthesised. Its structure is monoclinic, space group P21/n, with cell parameters a = 6.9031(8) A, b = 21.3213(16) A, c = 7.9833(9) A, β = 91.643(6)°, V = 1174.5(2) A3 and Z = 2 and consists of alternated stacking of donor and acceptor moieties along c. This compound is a semiconductor with a room temperature resistivity of 6.5 × 103 Ω cm and an energy gap 2Δ = 0.51 eV. The anisotropy and thermal dependence of the ESR signal, only due to the bedt-ttf cations, was studied in the range 4–300 K. The static and EPR spin susceptibilities indicate an almost temperature independent value of 2.5 × 10−4 emu/mol ascribed to a three-dimensional network of antiferromagnetic interactions.

Three new salts RBzPy+[Ni(α-tpdt)2]− (α-tpdt = 2,3-thiophenedithiolate, BzPy = benzylpyridine, R = H, Br, F) were prepared and structurally and magnetically characterized. A common structural feature of these compounds is the arrangement of the anions with thiophenic sulfur atoms connecting to a coordinating sulfur atom of a neighbouring anion, placed almost perpendicular to each other. The cations are positioned with the pyridine rings inserted between thiophenic rings of anions, maximizing π–π interactions. Depending on the cation substitution structural differences and variable degrees of cis–trans disorder in the anions are observed, which affect the magnetic properties. HBzPy[Ni(α-tpdt)2] displays dominant ferromagnetic interactions and cluster glass behaviour at low temperatures, BrBzPy[Ni(α-tpdt)2] shows dominant antiferromagnetic interactions with a magnetic anomaly at ∼6 K and FBzPy[Ni(α-tpdt)2] magnetic behavior is dominated by weak ferromagnetic interactions but without magnetic ordering down to 1.5 K.

Copper complexes with the 2,3-dicyano-5,6-dimercaptopyrazine ligand (dcdmp), Cu(dcdmp)2, were obtained in both monoanionic and dianionic forms as the tetrabutylammonium salts and were characterised, as well as a decamethylferrocenium salt of the dianion. (n-Bu4N)2Cu(dcdmp)2 crystallises in the triclinic system, space group P 1 ¯ , Z = 1, with unit cell parameters a = 9.9512(6) A, b = 10.541(1) A, c = 13.221(1) A, α = 69.756(9)°, β = 88.112(6)° and γ = 79.658(7)°. Its crystal structure consists of layers of well isolated square planar Cu ( dcdmp ) 2 − anions alternating with layers of n-Bu4N+ cations along b + c, and the magnetic properties in the range 2–300 K are close to those of an ideal paramagnet with an effective magnetic moment of 1.7 μB/f.u. n-Bu4NCu(dcdmp)2 crystallises in the monoclinic space group C2/c, Z = 8, with unit cell parameters a = 35.281(4) A, b = 9.501(1) A, c = 21.885(2) A and β = 109.842(9)°, being isostructural with the Au analogue previously described. The salt [Fe(Cp*)2]2[Cu(dcdmp)2] crystallises in the monoclinic system, space group C2/c, Z = 4, with unit cell parameters a = 15.891(1) A, b = 10.5133(7) A, c = 30.264(3) A and β = 91.105(2)°. Its crystal structure consists of out-of-registry columns, parallel to b, of alternated dianions and side-by-side pairs of cations, … A2−(D+D+)A2−(D+D+) … This compound behaves as a paramagnet with weak AF interactions and no ordering down to 1.7 K. The magnetic properties, due to both cation and anion S = 1/2 contributions, show a large anisotropy, ascribed essentially to the g-factor anisotropy of the Fe(Cp*)2cations.

The ground states of the quasi-one-dimensional organic metal (Per) 2 M(mnt)2 (where M = Au and Pt) were investigated by transport and magnetization measurements in magnetic fields of 33 and 45 tesla. The low field charge density wave transition temperature is suppressed by applied fields and a high field insulating state is introduced. We also report preliminary results of the effect of quasi-hydrostatic pressure on the charge density wave ground state and high field insulating state. The results will be discussed within the context of a contemporary model of high field density wave behavior.

The compounds RPt 4 B, with (R=La, Ce, Pr, Nd), were synthesized and their crystal structure was studied either by single crystal X-ray diffraction and/or by conventional and synchrotron X-ray powder diffraction. All four compounds of this family are isostructural and belong to the CeCo 4 B structure type. AC-susceptibility and magnetization studies show that: there is no magnetic ordering of the La compound down to 1.7 K; the Ce compound presents an antiferromagnetic-type-transition at 2.4 K; and both Pr and Nd compounds present a ferromagnetic-type transition at 4.2 and 4.9 K, respectively. Electrical resistivity studies show metallic behaviour for all compounds, the temperature dependence for the La compound being described by the Bloch Gruneisen relation. Thermopower studies as a function of temperature show that the thermopower is positive and small for these compounds, which is consistent with hole dominated metallic behaviour.

New binary compound Rh3B2−x, x = 0.167 crystallizing with its own structure type has been observed from the as cast alloys. The compound has a limited thermal stability range: it was found to decompose after annealing at 800 °C for 20 days. The crystal structure was investigated by X-ray diffraction from two single crystals using different techniques: CAD-4 automatic diffractometer, a = 5.470 (2), b = 6.816 (3), c = 9.068 (4), α = 110.74 (3), β = 94.81 (3), γ = 90.44 (2), 107 refined parameters, R 1 = 0.0418 , w R 2 = 0.1087 for 1223 reflections with I>2σ(Io), and BRUKER SMART AXS, a = 5.483 ( 4 ) , b = 6.818 (6), c = 9.072 (7), a = 110.78 (1), b = 94.73 (1), g = 90.46 (1), 107 refined parameters, R 1 = 0.0401 , w R 2 = 0.0959 for 943 reflections with I > 2 σ ( I o ) . The Rh3B2−x, structure (space group P 1 ¯ , Pearson symbol aP 30 - 1 ) is the first representative of structures with triclinic symmetry among binary borides and contains three different types of boron-boron aggregation: isolated boron atoms, B–B pairs and B6 chain fragments.

As an effort to explore new complexes of the 2,3-dicyano-5,6-dimercaptopyrazyne (dcdmp) ligand with different transition metals, different salts containing both the Au(dcdmp)2 − complex and the new species 2,3,7,8-tetracyano-1,4,6,9-tetraazothianthrene (tctata), were obtained and characterized. n-Bu4N Au(dcdmp)2 crystallises in monoclinic space group C2/c, Z=8 with unit cell parameters a=35.147(4), b=9.527(1), c=21.792(2) A and β=109.626(8)°. Its crystal structure consist of almost regular columns of [Au(dcdmp)2]−, stacked along b, surrounded by n-Bu4N+ cations. n-Bu4N AuBr2 (tctata) crystallises in triclinic space group P 1 , Z=2, with unit cell parameters a=10.986(1), b=13.230(2), c=13.791(1) A, α=79.150(9)°, β=69.663(6)°, γ=70.254(9)°. The crystal packing is made by zig-zag chains of tctata separated by layers of cations, with AuBr2 anions located in alternated cavities between the tctata chains and the cation layers. At last, n-Bu4N[Au(dcdmp)2] (tctata) crystallises in monoclinic space group P21/n, Z=4, with unit cell parameters a=10.693(2), b=40.308(7), c=10.870(1) A, β=92.16(1)°. Its crystal structure can be seen has a mix of those of the two preceding compounds. It consists of bidimensional layers composed of out of registry parallel zig-zag chains of alternating tctata and [Au(dcdmp)2]− units. The adjacent layers are separated by layers of [nBu4N]+. In the last two compounds the tctata appears as a planar molecule.

The crystal structures of PrRuSi 2 and Nd(Ru x Ni 1− x )Si 2 , x =0.75, 0.25 compounds were investigated by single crystal X-ray diffraction. The PrRuSi 2 compound belongs to the NdRuSi 2 structure type, and the atomic coordinates of the Nd(Ru x Ni 1− x )Si 2 compound are very close to those presented for the ternary TmLi 1− x Ge 2 compound, which is isotypic with NdRuSi 2 . The interrelation between CaSb 2 , PrRuSi 2 , Nd(Ru x Ni 1− x )Si 2 , CeNiSi 2 and ZrSi 2 structures is presented.

Three new radical salts, Per6[PMo12O40]·CH2Cl2 (1), Per6[PMo12O40]·CH3CN (2), and Per9(NBu4)4[SiW12O40]2 (3) (Per = perylene), have been synthesised and their electrical and magnetic properties characterised. These three salts are diamagnetic and they behave as semiconductors with room temperature conductivities of 69, 3.6 and 0.85 S cm−1. While salt 2 presents hole-type conduction and 3 exhibits electron-dominated electrical transport properties, salt 1 shows at 150 K an abrupt change in the thermal dependence of the electrical conductivity and the Seebeck coefficient suggesting a phase transition.

The crystal structure of the Nd 2 Os 3 Si 5 compound was refined from single-crystal X-ray diffraction ( P 4/ mnc space group, a =10.762(5) A, c =5.796(2) A) down to R =0.0662 for 393 reflections with F 0 >4σ( F 0 ). This compound belongs to a partly disordered U 2 Mn 3 Si 5 type structure: the Si2 site has been refined with a split position x , y , z (16 i ) instead of x , x +1/2,1/4 (8 g ), and for an occupancy of 50%. X-Ray single-crystal investigations of the PrOs 2 Si 2 and Ce(Ru 0.6 Os 0.4 ) 2 Si 2 compounds were also performed for the first time. Both compounds crystallize in the CeGa 2 Al 2 structure type, I 4/ mmm space group, with a =4.1678(4) A, c =9.901(1) A, R =0.0433 and a =4.173(1) A, c =9.797(3) A, R =0.0393, respectively.

The crystal structure of a new ternary boride Ce 2 Ir 5 B 2 , space group R 3 m , a =5.477(2) A, c =31.518(5) A, Z =6, V =818.79 A, was refined down to R =0.0484, wR 2 =0.1211 from single crystal X-ray diffraction data. This is the first representative of a new structure type of intermetallic compounds (an ordered variant of the binary Er 2 Co 7 compound). The structure of Ce 2 Ir 5 B 2 is the stacking variant of the MgCu 2 - and CeCo 3 B 2 -type slabs and belongs to the structural series with the general formula R 2+ n M 4+3 n X 2 n ( n =2).

The ternary compound UFe 7 Al 5 was synthesized by arc melting, followed by annealing at 850°C. The crystal structure was determined by single-crystal X-ray diffraction and refined to a residual value of R =0.039 ( S =1.030), with lattice parameters a =8.581(2) A and c =4.946(1) A. This compound is a new extreme composition in the family of intermetallics with general formula UFe x Al 12− x crystallizing in the tetragonal ThMn 12 -type structure, space group I 4 /mmm . In contrast to UFe x Al 12− x within the composition range 4⩽ x ⩽6, in UFe 7 Al 5 the additional iron atom is found in the 8 i equipositions. Magnetization measurements versus temperature show two magnetic transitions at 363 and 275 K, respectively, with a ferromagnetic behavior below the highest temperature transition. 57 Fe Mossbauer data indicate that the high-temperature transition is related to the ordering of the iron atoms. The dependence of the isomer shifts and magnetic hyperfine fields on the crystallographic site and on the number of the iron nearest neighbors is similar to that observed in the other UFe x Al 12− x and rare-earth analogues. The magnetic hyperfine field values of iron atoms on 8 i sites is larger than in the other sites, in agreement with previous data obtained for other ThMn 12 -type compounds.

The charge transfer salt (DT-TTF)4[Au(pds)2]3 (DT-TTF, Δ2,2′-bithieno[3,4-d]-1,3-dithiol; pds, pyrazine-2,3-diselenate) was prepared and characterised by X-ray diffraction, electrical conductivity, thermoelectric power, magnetic susceptibility and EPR measurements. This compound crystallises in the triclinic system, space group P 1 , with the unit cell parameters a=9.712(5) A, b=13.620(5) A, c=17.169(5) A, α=97.254(5)°, β=106.132(5)°, γ=95.956(5)°, V=2141.10(15) A3, Z=1. Its crystal structure consists of a bidimensional network of DT-TTF tetramers and orthogonal anions. The electrical properties indicate it is a small gap semiconductor (2Δ=190 meV), with a room temperature conductivity of σRT=2 S cm−1. The electrical and magnetic properties reveal two types of transitions occurring upon cooling. The first, at 238 K, as a second order change to a large gap semiconducting state and, a lower transition, of first order type, with a large hysteresis between 210 and 150 K, probably associated with a larger structural change in the DT-TTF network.

The ( n -Bu 4 N) 2 [Fe(dcbdt) 2 ] 2 complex, where 4,5-dicyanobenzene-1,2-dithiolate (dcbdt), was prepared and characterised by X-ray diffraction, Mossbauer spectroscopy and magnetisation measurements. The crystal structure as determined by single crystal X-ray diffraction is triclinic, space group P 1 with cell parameters a =9.5660(1) A, b =13.0200(2) A, c =16.0850(2) A, α =67.554°(1), β =86.797°(1), γ =70.523°(1), V =1738.77(4) A 3 and it consists in strongly dimerised [Fe(dcbdt) 2 ] − units, which are stacked side by side as chains along a . The magnetic susceptibility shows that the [Fe(dcbdt) 2 ] − units have a low spin S =1/2 configuration and, besides a strong intradimer antiferromagnetic interaction, present also a significant interdimer antiferromagnetic interaction mediated by short side contacts.

The synthesis and characterisation of two new radical ion salts based on the donor dithiophenetetrathiafulvalene (DT-TTF) and the anion Au(cdc)2 − (cdc=cynanodithioimido carbonate) are described. These salts were characterised as the mixed valence compound (DT-TTF)2(Au(cdc)2) (1) and the completely ionic salt (DT-TTF)(Au(cdc)2) (2). The X-ray crystal structure of both compounds show that they are formed by chains of donor molecules separated by anions, but, whereas in compound 2 the donors form uniform stacks, in compound 1 they are dimerised. The electrical conductivity measured in a single crystal at room temperature is 0.2 S cm−1 for 1 and 1.7×10−2 S cm−1 for 2, both revealing semiconducting behaviour. Magnetic measurements indicate strong antiferromagnetic interactions between the donors in compound 2, and a possible spin-Peierls transition at low temperature for compound 1.

The M(tdas)2 complexes (tdas2−=1,2,5-thiadiazole-3,4-dithiolate) with M=CuII, CuIII and AuIII were obtained as tetrabuthylammonium and tetraphenilphosphonium salts and characterised. The crystal structure of (n-Bu4N)n[M(tdas)2], M=Cu(2) and Au(4) were determined by X-ray crystallography as well as that of the charge transfer salt (TTF)2[Au(tdas)2]2 (5).

Two new families of charge transfer solids based on transition metal bis-maleonitrile dithiolate complexes [M(mnt)2]n− and two tetrathiatulvalene (TTF) derivatives containing external sulfur atoms have been synthesized and characterized as (BMDT-TTF)2[M(mnt)2] and (EDT-TTF)[M(mnt)2], where BMDT-TTF stands for bis(methylenedithio)-tetrathiafulvalene, EDT-TTF for ethylenedithio-tetrathiafulvalene and M=Au, Pt and Ni. The salts of the series (BMDT-TTF)2[M(mnt)2] are quasi-isostructural and crystallize forming mixed ADDA stacks along a+b. In the (BMDT-TTF)2[Au(mnt)2] salt, the anion complex is diamagnetic and has a formal charge of −1, whereas in Ni salt the anion has a charge of −2, being also diamagnetic. The magnetic properties of the Au salt follow a 1D antiferromagnetic Heisenberg model modified with a molecular field. The salt with Ni displays very strong antiferromagnetic interactions. The (EDT-TTF)[M(mnt)2] salts with M=Ni and Pt are isostructural and crystallize forming alternated DADA stacks. The anions, with a formal charge of −1, are paramagnetic with a spin 1 2 ;. Their magnetic susceptibility can be successfully simulated within the antiferromagnetic uniform chain model of Heisenberg. Lastly, (EDT-TTF)[Au(mnt)2] crystallizes in the triclinic space group P(-1) forming also alternated stacks along c in which the EDT-TTF molecules are 50% disordered.

The study of the magnetic properties of molecular conductors has experienced, during the last decades, a very significant evolution, comprising systems of increasing molecular complexity and moving towards multifunctional materials, namely by their incorporation in conducting networks of different paramagnetic centers.[...]

[U(Tp(Me2))2(bipy˙)], a uranium(III) complex with a radical bipyridine ligand which has magnetic properties with contributions from both the ligand and the metal, presents slow relaxation of the magnetisation at low temperatures, already under zero static magnetic field, and energy barriers slightly above the non-radical analogues.

The quaternary borocarbides TmNi 2 B 2 C and UNi 2 B 2 C crystallize in the body-centered tetragonal LuNi 2 B 2 C-type structure, and exhibit antiferromagnetic order below 1.53 and 218 K, respectively. The magnetic structure of TmNi 2 B 2 C is characterized by incommensurate, long-range, spin-density-wave in the basal plane, with Tm moments along the c -axis, and does not involve ferromagnetic basal planes, while that of UNi 2 B 2 C is assumed to contain U moments along the c -axis in ferromagnetic basal planes. In the system (U,Tm)Ni 2 B 2 C the different magnetic structures of the end compounds result in a frustration of magnetic moments, which is not just directional. Indeed, the newly-prepared intermediate solid solution (U 0.50 Tm 0.50 )Ni 2 B 2 C is paramagnetic down to 2 K, for both as-cast and annealed samples, with no indication for any cooperative phenomenon. The paramagnetic values of the annealed sample [ θ =−5.6(5) K, μ eff =5.4(1) μ B ] are compatible with those of the end compounds.

Phase equilibria were established in the Y–Fe–Al ternary system within the concentration region 50–100 at.% Al for an isothermal section at 1070 K by means of scanning electron microscopy and powder X-ray diffraction. Two ternary aluminides were observed, YFe x Al 12− x (4≤ x ≤5.6) with the ThMn 12 -type structure, a =8.6467(9)–8.7604(7) A, c =5.0374(6)–5.0504(5) A and YFe 2 Al 10 , YbFe 2 Al 10 -type structure, a =8.9649(6) A, b =10.1568(6) A, c =9.0113(6) A. The only binary which forms a prolonged solid solution range is YAl 2 . The unit cell edge of the YFe x Al 2− x compounds, MgCu 2 -type structure, decreases with Fe content from 7.834(9) A for x =0 down to 7.689(4) A for x =0.5. 57 Fe Mossbauer spectroscopy data of YFe 2 Al 10 show an unusually large isomer shift for Fe in Al-containing intermetallics and confirm that no magnetic ordering occurs down to 5 K.

Polycrystalline (U 1− x Th x ) 2 Pt 2 In solid solutions with x =0.03, 0.05, 0.08 and 0.10 were synthesized by arc melting the constituents under a purified Ar atmosphere. All the compounds crystallize in a tetragonal U 3 Si 2 -type structure, with the space-group P4/mbm , ( Z =2). The effects of Th substitution for U on the magnetic properties suggest pronounced electron correlations as in the heavy fermion U 2 Pt 2 In. However, no clear indication of magnetic ordering in all the compounds was found. The magnetic phase transitions around 3 and 19 K, found by means of ac-susceptibility and magnetization measurements are most likely due to the presence of minority phases.

AFexAl12−x intermetallics (AY, Tm, Lu and U, 4≤x≤4.3) were synthesized as polycrystalline material and as large single crystals by the Czochralski method from bulk charges containing A, Fe and Al in the atomic ratios 1/4/8. The purity of the studied samples was checked by powder X-ray diffraction and their final composition was estimated using the Rietveld method of structure refinement. The 57Fe Mossbauer spectra of samples with final composition x>4 have revealed that the Fe atoms on the same crystallographic site may have different magnetic moments, μFe, whose values increase with the number of Fe nearest neighbours. The strong sensitivity of the μFe on small deviations from the ideal 1/4/8 stoichiometry has clearly shown that while the single crystals of UFe4Al8 grown by the Czochralski method have the expected composition, those grown from YFe4Al8 and LuFe4Al8 bulk charges have actual compositions YFe4.2(1)Al7.8(1) and LuFe4.2(1)Al7.8(1) thus explaining contradictory results that have been previously published.

New Ni and Au complexes with 2,3-dihydro-5,6-thiophenedithiolate (dtpdt) 2,3-thiophenedithiolate (a-tpdt), and 3,4-thiophenedithiolate (tpdt) have been prepared and characterised. Their ability to be used as building blocks for novel conducting and magnetic materials is demonstrated by different new compounds, the most remarkable being Au(α-tpdt) 2 , a neutral complex exhibiting metallic properties. Several magnetic materials were obtained as salts with decamethyl metallocene cations. The magnetic field/temperature phase diagram of [Fe(Cp * ) 2 ][Ni(α-tpdt) 2 ] is presented.

The preparation, structures and physical properties of the organic/inorganic radical salts based upon perylene (per) and Lindquist type polyoxometalates (POMs) are reported. Three new hybrid salts have been prepared: (per)5[Mo6O19] (1), (per)5[W6O19] (2), and (per)5[VW5O19] (3). Only structures 1 (P, Z = 2) and 3 (P, Z = 2) were fully determined as compound 2 was found to have unit cell parameters practically identical to 1 and, therefore, is considered isostructural with the latter. The structures consist of interpenetrated organic and mixed organic/inorganic layers in the ac plane alternating along the a direction. The organic layers present a novel packing mode of the perylene molecules that consists of criss-cross chains formed by two alternating dimers running along the c axis. Besides the ability to induce novel packings in the organic sublattice, the possibility offered by the POMs of varying the charge while maintaining the size and shape of the anion has enabled the control of the electronic band filling and, therefore, of the electrical and magnetic properties. Thus, salts 1 and 2, where the anionic charge is −2, are diamagnetic and present lower room temperature conductivities, while salt 3, where the anionic charge is −3, has an unpaired electron and presents a higher room temperature conductivity and a lower activation energy. Thermopower measurements show that salts 1 and 2 present hole-type conduction whereas salt 3 exhibits electron-dominating electrical transport.