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The importance of C–H⋯NC interactions, which although generally considered weak, are effective in the self-assembly of crystal structures.

Bilayer CNB-EDT-TTF salts with different polymeric anions.

The family of recently described salts based on the electron donor CNB-EDT-TTF (5-cyanobenzene-ethylenedithio-tetrathiafulvalene) and different anions A, with general formula (CNB-EDT-TTF)4A, constitutes an unprecedented type of molecular conductor based on a bilayer structure of the donors. The crystal structures of the bilayer conductors (CNB-EDT-TTF)4A with small discrete anions are reviewed and analyzed considering previously reported compounds with different anions (A = I3−, ClO4−, BF4−, ReO4−, PF6− and SbF6−), as well as three new members of this family described here with AsF6−, AuI2−and I2Br−. A common structural feature of this family of compounds is the head-to-head arrangement of the donors, induced by a network of weak CN⋯H–C interactions, which can be described as an effective combination of R22(10) and R24(10) synthons, forming donor bilayers alternating with anionic layers. The magnitude of the interactions associated with R22(10) and R24(10) synthons is estimated to be 4.7 and 10.0 kcal mol−1, respectively. In spite of the common donor bilayer arrangement, a rich diversity of structural variations and polymorphs is observed. These structures are related to different types of donor or anion arrangements, which are analyzed. For all anions a β′′-type packing pattern of the donor molecules arranged in virtually identical bilayers is observed. However, for (CNB-EDT-TTF)4I3, so far a unique exception in this family of compounds, a distinct κ-type packing of the donors, is also obtained as a metastable phase as shown also by DFT calculations that predict the κ-phase above the β′′-phase. Another type of polymorphism is observed in β′′-(CNB-EDT-TTF)4A, compounds with tetrahedral anions, related to the tilting of the donor molecules (either alternating or uniform) in successive bilayers, leading to monoclinic or triclinic unit cells, with doubling of one cell parameter corresponding to the thickness of one bilayer (∼25 A). Finally, the anions, which often appear with fractional site occupation factors, can be ordered in the anionic plane, with different degrees of correlation between successive anion planes as shown in the AsF6.compound. The implications of these structural features in the electronic properties of these compounds are also discussed.

Four new charge transfer salts based on tetrathiafulvalene (TTF) or tetramethyltetraselenafulvalene (TMTSF) donors and transition metal complexes [M(dcdmp)2] (dcdmp = 2,3-dicyano-5,6-dimercaptopyrazine), TMTSF5[Cu(dcdmp)2]4 (1), (TMTSF)2[Ni(dcdmp)2] (2), and (TTF)7[M(dcdmp)2]6 (M = Au (3) and Cu (4)) were prepared by electrocrystallization. These compounds are characterized by a rich variety of crystal structures with unusual donor/acceptor stoichiometries. In spite of the uncommon structural types observed, these salts can be highly conducting. Compound 1 crystallizes with segregated TMTSF stacks, showing 1D metallic properties with a room temperature conductivity of 134 S/cm. Compound 2 crystallizes in an out-of-registry mixed column arrangement of donor dimers and acceptors. Compounds 3 and 4 appear in single crystal X-ray diffraction as isostructural and composed of columns of TTF hexamers that are disrupted by a single TTF layer and surrounded by [M(dcdmp)2]− monoanionic pairs, aligning perpendicular...

Two salts of the dissymmetric TTF-derivative 4-cyanobenzene-ethylenedithio-tetrathiafulvalene (4-CNB-EDT-TTF) with bromide and tribromide anions and with different stoichiometries, namely, (1:1) (4...

A new isomer of the dissymmetric TTF derivative, 4-cyanobenzene-ethylenedithio-tetrathiafulvalene (4-CNB-EDT-TTF) (1), was prepared and compared with the previously reported 5-CNB-EDT-TTF. 1 was obtained in high yield, by a cross-coupling reaction with triethyl phosphite between 2-oxobenzo[d][1,3]dithiole-4-carbonitrile (Ia) and 5,6-dihydro-[1,3]dithiolo[4,5-b][1,4]dithiine-2-thione (Ib). The key compound for the synthesis of the ketone Ia was thione 2-thioxobenzo[d][1,3]dithiole-4-carbonitrile (Ia′), both compounds are reported. 1 as a new electron donor was characterized namely by cyclic voltammetry, NMR, UV-visible, IR and by single crystal X-ray diffraction. It crystallizes into two polymorphs (α-1 and β-1) with structures dominated by a large number of S-, C-, and N-mediated short contacts. One of the polymorphs (β-1) is present as a combination of C–N⋯H–C interactions associated with a head-to-head arrangement of donor molecules in paired layers (bilayers) described as weaker and stronger R23(10) synthons. A radical cation salt formulated as (4-CNB-EDT-TTF)I3 (2) was obtained by slow diffusion of solutions of the donor and iodine. In this salt, the (4-CNB-EDT-TTF)˙+ radical cations are associated into dyads with a strong pairing of the radical species in a singlet state. In 2, the donor dimers are connected to adjacent dimers through C–N⋯H–C interactions described as an R22(10) synthon. They present different sources of disorder on the carbon atoms of the dihydrodithiin ring, in the CN group position and on one of the triiodide anions. No relation between the disorders of the triiodide anions and the CN group positions was detected.

Four salts of the dissymmetric TTF-derivative 4-cyanobenzene-ethylenedithio-tetrathiafulvalene (4-CNB-EDT-TTF) with different anions, namely (4-CNB-EDT-TTF)A with A = ClO4 (1), BF4 (2) and (4-CNB-EDT-TTF)2[M(mnt)2] with M = Ni (3) and Au (4), were obtained by electrocrystallization and characterized by single-crystal X-ray diffraction, magnetic susceptibility and electrical conductivity measurements in comparison with the analogues based on the donor 5-CNB-EDT-TTF. All the compounds present dimerization of the donor units. Compounds 1 and 2 are isomorphous with a crystal structure characterized by slipped head to tail donor dimer stacks segregated from anion columns. Compounds 3 and 4 are isostructural with a crystal structure characterized by alternated stacks of head to tail donor dimers and acceptors. In spite of the different structural types and stoichiometries, all of these compounds have CN⋯H pairing interactions associated with R22(8), R24(8), R22(10), and R24(10) synthons between donors in nearby dimers. 3 and 4 are semiconductors, and their magnetic susceptibility exhibits a behaviour typical of antiferromagnetically coupled spin chains with magnetic exchange values J/k = −149.9 and −60.1 K, respectively, and in the case of 3, a Curie–Weiss contribution from the paramagnetic anions [Ni(mnt)2]−.

(CNB-EDT-TTF)6Ag∼7.91I∼9.15 (CNB-EDT-TTF = 5-cyanobenzene-ethylenedithio-tetrathiafulvalene) is reported as the first bilayer conducting salt with a polymeric anion. The anion is a silver-deficient iodoargentate layered polymer with a composition close to Ag7.95I9.19, as deduced from single crystal X-ray diffraction. In spite of disorder in the silver iodide polyanion layer, and the large unit cell with six inequivalent donor molecules, this compound presents clear metallic properties down to 1.5 K, comparable to those of the β′′-type 4:1 salts of this donor with small discrete anions, with room temperature electrical conductivity in the range of 3–10 S/cm and thermoelectric power of ∼100 μV/K., This work was funded through FCT (Portugal) through Research Contract UID/Multi/04349/2013, LISBOA-01-0145-FEDER-029666 and UIDB/04564/2020. Work in Spain was supported by MICIU (PGC2018-096955-B-C44), MINECO through the Severo Ochoa Program (SEV-2015-0496) and Generalitat de Catalunya (2017SGR1506).

The electrocrystallization from dichloromethane or tetrahydrofuran solutions of the dissymmetrical bis(ethylenedithio)tetrathiafulvalene (ET) derivative cyanobenzene–ethylenedithio–tetrathiafulvalene (CNB-EDT-TTF) in the presence of perchlorate anion ClO4– affords two different polymorphs of salts with 4:1 stoichiometry, a previously described triclinic phase β″T-(CNB-EDT-TTF)4ClO4 (1a), and a new monoclinic phase β″M-(CNB-EDT-TTF)4ClO4, (1b), as well as a compound with 1:1 stoichiometry, (CNB-EDT-TTF)ClO4 (2), depending on the solvent and crystallization conditions. The special conditions necessary for the growth of the unusual 4:1 salts, requiring low current densities to oxidize the donors and subsequent slow diffusion controlled association processes, are discussed. Both 4:1 polymorphs present a bilayer structure of the donors induced by head-to-head C–N···H pairing interactions associated with a combination of R22(10) and R24(10) synthons between donors in nearby layers. These polymorphs share the sa...

Two new members of the family of bilayer compounds (CNB-EDT-TTF)4X, (CNB-EDT-TTF = 5-cyanobenzene-ethylenedithio-tetrathiafulvalene) with anions X = ReO4− and SbF6− are reported, their electron transport and optical properties investigated, and then compared to the ClO4− salt that was previously described. These compounds share the same structural type, i.e. bilayers of donors, which are packed in a β”-type pattern and then separated by layers of highly disordered anions. The absolute values of the electrical resistivity measured in single crystals within the layers were found in the range of 5 to 18 (cm)−1, with a significantly sample dependence being ascribed to intrinsic disorder effects. The ClO4− and SbF6− salts exhibit metallic behavior with the resistivity decreasing upon cooling almost linearly with temperature until a broad minimum is reached between 15 and 80 K, depending on crystal quality; this is followed by an upturn of resistivity reaching values at T = 1.5 K that were comparable to those attained at room temperature. The electrical resistivity of the ReO4− salt follows a thermally activated behavior already at T = 300 K, although with a small activation energy in the range 16−18 meV. Thermoelectric power measurements yield large positive values (75−80 µV/K) at ambient temperature with a metallic behavior that is identical for all compounds. Temperature and polarization dependent infrared reflection measurements on single crystals of (CNB-EDT-TTF)4X salts, with X = ClO4−, ReO4−, and SbF6−, have been performed to obtain the optical conductivity and analyze the electronic and vibrational properties. For (CNB-EDT-TTF)4ClO4 the molecular vibrations exhibit a significant variation below T = 23 K, which suggests a charge localization phenomena.

The charge transfer salts α-DT-TTF[Au(dcdmp)2] (1), BET-TTF[Au(dcdmp)2] (2M and 2T), α-DT-TTF[Cu(dcdmp)2] (3), ET[Cu(dcdmp)2] (4), (BET-TTF)2[Cu(dcdmp)2] (5), (ET)2[Ni(dcdmp)2] (6), and α-mtdt[Cu(dcdmp)2] (7) were obtained by electrocrystallization of different electron donor molecules derived from TTF (α-DT-TTF = alpha-dithiophene-tetrathiafulvalene; BET-TTF = (bis(ethylenethio)tetrathiafulvalene; ET = bis(ethylenedithio)-tetrathiafulvalene; α-mtdt = alpha-methylthiophenetetrathiafulvalene) in the presence of transition metal complex [M(dcdmp)2] (M = Au (III), Cu (III) and Ni (II)) (dcdmp = 2,3-dicyano-5,6-dimercaptopyrazine). Compounds 1 and 2 (2M and 2T) have a similar packing pattern composed of mixed stacks of alternating donor-acceptor molecules. For (BET-TTF)[Au(dcdmp)2] two different crystal structures (2M and 2T) were obtained indicating polymorphism. Compounds 3 and 4 are isostructural being composed of zigzag chains of alternating donor and acceptor molecules. The salts with a 2:1 stoichiometry, (BET-TTF)2[Cu(dcdmp)2] (5), and (ET)2[Ni(dcdmp)2] (6) present the donor molecules fully oxidized and [M(dcdmp)2] (M = Ni and Cu) in a dianionic state. The salt of the dissymmetric donor α-mtdt with [Cu(dcdmp)2], α-mtdt[Cu(dcdmp)2] (7) has a crystal structure composed of segregated donor stacks that are positioned in a head-to-head fashion and alternate with the anion stacks. All charge transfer salts (1–7) are modest semiconductors with conductivities in the range 10−1–10−5 S/cm, with the highest values obtained in α-DT-TTF salts, compounds 1 and 3.

The preparation and characterization of new salts based on the dissymmetrical TTF derivative CNB-EDT-TTF (cyanobenzene-ethylenedithio-tetrathiafulvalene) and BF4− anions, are reported. Depending on the electrocrystallization conditions salts with different stoichiometries, (CNB-EDT-TTF)BF4 and β”-(CNB-EDT-TTF)4BF4, can be obtained. The 1:1 salt is an electrical insulator isostructural to the ClO4 analogue previously described. The 4:1 salt is a new member of the family of 2D metals of this donor with different small anions X, (CNB-EDT-TTF)4X, characterized by a bilayer arrangement of the donors and it was obtained in a monoclinic polymorph with a β”-type donor packing pattern. The small anions in this compound are severely disordered between the donor bilayers, which present slightly larger lattice parameters than the isostructural ClO4 analogue. Both electrical conductivity and thermoelectric power measurements in single crystals denote metallic properties as predicted by electronic band structure calculations. As a consequence of the anion disorder the metallic regime of the electrical conductivity denotes electronic localization effects with a progressive increase of resistivity below ~25 K. Because of the larger lattice parameters the intermolecular interactions and electronic bandwidth are decreased compared to other (CNB-EDT-TTF)4X salts. The large and positive thermoelectric power S of this compound (~110 μV/K in the range 100–330 K) and its electrical conductivity σ = 20 S/cm at room temperature lead to a power factor S2σ = 24 μW/K2m, quite large among molecular conductors, placing these compounds as potential candidates for thermoelectric materials., This work was supported by FCT (Portugal) through contract UID/Multi/04349/2013 and grants to SO (SFRH/BD/72722/2010) and S.R. (SFRH/BPD/113344/2015). Work in Bellaterra was supported by MINECO (Spain) through Grant FIS2015-64886-C5-3-P as well as the Severo Ochoa Centers of Excellence Program under Grant SEV-2015-0496, and by Generalitat de Catalunya (2017SGR1506).

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.

(DT-TTF)[Cu(dcdmp)(2)] (1), (DT-TTF)(2)[Cu(dcdmp)(2)] (2), and (DT-TTF)(3)[Cu(dcdmp)(2)](2) (3) are three new charge transfer salts obtained by electrocrystallization of the donor DT-TTF (dithiophene-tetrathiafulvalene) with the diamagnetic copper complex [Cu(dcdmp)(2)](-) (dcdmp = 2,3-dicyano-5,6-dimercaptopyrazine). Compounds 1 and 3 crystallize in the triclinic system and consist of out-of-registry layers of mixed stacks of donor and acceptor molecules. (DT-TTF)(2)[Cu(dcdmp)(2)] presents a structure similar to the parent spin-ladder systems with donor stacks arranged in pairs; however, a magnetic spin-ladder behavior is not observed probably due to strong interactions between pairs. Compound 3, despite the mixed nature of the stacks, displays relatively high conductivity (7 S/cm) due to a one-dimensional network of interactions between donors., This work was supported by FCT (Portugal) through contracts PTDC/QEQ-SUP/1413/2012 and UID/Multi/04349/2013 and by DGI, Spain (CTQ2013-40480), the Generalitat de Catalunya (2014SGR0017), the CIBER de Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), promoted by ISCIII, Spain. R. A. L. S. is thankful to FCT for the PhD grant SFRH/BD/86131/2012.

1H and 195Pt NMR are used to probe the spin ½ anion chain in the quasi-one-dimensional conductor Per2[Pt(mnt)2], which exhibits nearly simultaneous charge density wave (CDW) and spin-Peierls (SP) transitions at low temperatures (Tc ~ 8 K). Below Tc the [Pt(mnt)2] chain forms a spin-singlet state that is evident in 1H NMR spectra and spin relaxation (1/T1) rates; however minority unpaired Pt spins may remain in the SP ground state. With increasing magnetic field, the SP and CDW order parameters decrease in unison, indicating they are coupled up to a critical field Bc ~ 20 T. Above Bc, the spin singlet evolves into a spin-polarized configuration. The 195Pt NMR signals vanish as either Tc or Bc are approached from within the SP ground state, suggesting the hyperfine field of the Pt nucleus is significantly stronger than at the proton sites. Simulations yield a consistent picture of the angular, temperature, and magnetic field-dependent spectral features.

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 study of the family of compounds α-(Per)2[M(mnt)2], (M = Cu, Au, Ni, Pd, Pt, Co, Fe) has started more than 30 years ago with the report of first members, but has been always limited by difficulties in the growth of high quality and large single crystals. These compounds can be obtained by oxidation of perylene in the presence of anion salts, either with iodine or electrochemically. The electrocrystallisation, which usually yields better quality crystals than the chemical oxidation route, has however several limitations and it is significantly more difficult to apply to these perylene compounds, which may present different stoichiometries and polymorphs, than to charge transfer salts of many other donors. These difficulties are associated with the low solubility of perylene and the instability of its radical cation in solution. The results of a systematic study to optimise the growth conditions of these compounds by electrocrystallisation and to identify key factors governing the formation of their different phases are presented. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The first stages of the electrocrystallization of (Per)(2)[Au(mnt)(2)] salt from dichloromethane on gold, platinum, and highly orientated pyrolytic graphite (HOPG) were investigated by cyclic voltammetry, atomic force microscopy, and X-ray photoelectron spectroscopy in order to understand the determinant factors for nucleation and crystal growth. The crystal growth occurs from adsorbed films of dithiolate on gold or platinum and of perylene on HOPG, after homogeneous nucleation, and it is controlled by the low diffusion of the species toward the growing surface.

The optical properties of the one-dimensional organic conductor (perylene)2Pt(mnt)2 and its Au analogue have been investigated at ambient and low temperatures. The spectra along the stacks of the molecules show a simple Drude behavior with no detectable influence of electron-electron interactions. Basing on the spectra for different polarizations an assignment of the vibrational modes is made. Perpendicular to the stacks, a wide band observed in the mid-infrared range evidences a charge transfer between perylene and anion stacks. The electronic properties are discussed in comparison with other quasi-one-dimensional synthetic metals.

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.

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.

The conditions for obtaining single crystals of Per2Pt(mnt)2 via an electrochemical process are described. The occurrence of a lower conductivity β-phase cannot be avoided. Thermal dependence of resistivity and thermopower of β-Per2Pt(mnt)2 is reported and results discussed in comparison with previously known β-phase members (M=Cu and Ni) of the Per2M(mnt)2 family.

The semi-ordered alloys with compositions UFe x Al 12− x ( 4.5 ⩽ x ⩽ 5.0 ) and UFe 4 Al 8− x Ga x ( x = 1.0 and 1.5) were prepared by induction melting and found to crystallize in the tetragonal ThMn 12 -type structure (space-group I4/mmm). The comparative study of magnetic properties showed that the magnetic behaviour in UFe 4 Al 8− x Ga x as Al is replaced by Ga is similar to that observed in UFe x Al 12− x with the increase of Fe concentration. In both cases an increase of the ordering temperature, T ord , and saturation magnetization, M sat , as well as an enhancement of the ferromagnetic character are detected. The presence of a second magnetic transition below T ord is also observed both in UFe x Al 12− x and in the Ga-containing compounds. The Rietveld refinement of X-ray powder diffraction data and the analysis of the Mossbauer spectra are consistent with the occupation of the 8f and 8j sites by Fe atoms in both series. The similarities between the magnetic behaviour of the UFe 4 Al 8− x Ga x and UFe x Al 12− x are related rather to the fraction of 8j sites occupied by Fe than to the total Fe content of the samples.

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.

The ternary compound UFe3Al9 was synthesized by arc melting, followed by annealing at 850 °C. The crystal structure was determined by single-crystal X-ray diffraction and refined down to a residual value of R = 0.0 4 3 ( R W = 0.0 9 9 , S = 0.8 9 ), with lattice parameters a = 8.8 3 7 3 ( 2 ) A and c = 5.0 7 3 8 ( 2 ) A . This phase is a new boundary composition in the extended range of solubility with general formula UFexAl12−x crystallizing in the tetragonal ThMn12-type structure, space group I4/mmm, with the iron atoms partially occupying the equivalent 8f positions. AC-susceptibility and magnetization measurements seem suggestive of a ferromagnetic type of transition at T ≈ 2 5 K , but specific heat and 57Fe Mossbauer data indicate that neither long-range magnetic ordering nor standard spin-glass behaviour is associated with the magnetic anomaly. The presence of few iron-rich clusters with short-range ferromagnetic-like order at low temperatures is proposed for UFe3Al9.

The quasi-one-dimensional (Q1D) materials, (Per)2M(mnt)2, have transition temperatures of 12 and 8 K for M=Au and Pt, respectively, as samples are cooled from a metallic state to an insulating, charge density wave (CDW) ground state. In these proceedings, we present results regarding the effect of quasi-hydrostatic pressure and high magnetic fields on the CDW and field-induced density wave (FIDW) states of these materials. With pressures greater than 4 kbar, Shubnikov de Haas oscillations appear in the M=Au compound, which reach the n=1 Landau level before the limit of the applied magnetic field. While lower field (B

The charge transfer salts (DT-TTF)2[Ni(dcdmp)2], (DT-TTF)3[Cu(dcdmp)2]2 and (DT-TTF)3[Au(dcdmp)2]2, (dcdmp=2,3-dicyano5,6-dimercaptopyrazine) were obtained by electrocrystallisation and characterized. The Ni compound presents a structure consisting of stacks of fully oxidized donor pairs alternating with dianionic complexes. In the two other compounds the complex is monoanionic, the Au salt presenting a structure with stacks of donors triads alternating with pairs of complexes. All compounds display a semiconductor behavior with the highest electrical conductivity of 6.8 S/cm at room temperature being observed for the Cu salt.

Chemical vapor deposition (CVD) and electrodeposition (ED) were applied to grow thin films of molecule-based magnets and conductors. Chemical vapor deposited films are illustrated by the M(TCNE)x (M=V, Cr, Nb, Mo) magnet series. V(TCNE)x and Cr(TCNE)x are room-temperature magnets. XANES/EXAFS studies on the air-stable Cr(TCNE)x have been performed to determine the chemical environment of the chromium within the polymeric network. Electrodeposition on a silicon working electrode was applied to process thin films of numerous molecule-based conductors, namely, non-integral oxidation state compounds, charge transfer complexes, and singlecomponent molecular conductors. Among the series of conductive thin films, TTF[Ni(dmit)2]2 and Ni(tmdt)2 exhibit a metal-like behavior.

(n-Bu)4N[Fe(qdt)2] provides the first example of an undimerised FeIII bisdithiolene complex with well isolated square planar coordinated [Fe(qdt)2]− units, due to short apical Fe⋯H, Fe⋯C and S⋯H contacts with the cations, while the tetraphenylarsonium salt of this complex presents the usual dimerisation as [Fe(qdt)2]22−, with square-based pyramidal coordination of Fe.

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 Charge-Density-Wave (CDW) transition temperature T CDW of quasione-dimensional conductors Per 2 M(mnt) 2 (M=Au, Pt) steeply decreases with increasing pressure up to 0.5 GPa but the pressure-induced transition to a metallic state is not observed at least up to 1.5 GPa. At ambient pressure the resistance decreases with decreasing temperature but turns to increase at the temperature T min corresponding to the resistance minimum, and then it exponentially raises below T CDW . T min initially decreases steeply with increasing pressure but becomes nearly constant at pressures above 0.5 GPa, where T CDW disappears. Nonlinear conduction is observed under pressures above 1 GPa and at temperatures below 4.2 K. The present results are discussed in terms of the pressure-induced quantum melting of the CDW state.

Starting from the first organic spin ladder reported, a dithiophene-tetrathiafulvalene salt ((DT-TTF)2[Au(mnt)2]) (mnt = maleonitriledithiolate), two different approaches to enlarge the family of organic spin-ladder systems are described. The first approach consists of a molecular variation of the donor; to that purpose, the new TTF derivative ethylenethiothiophene-tetrathiafulvalene (ETT-TTF, 3), is synthesized and structurally characterized. From this donor a new ladder-like structure compound, (ETT-TTF)2[Au(mnt)2] (4), isostructural with (DT-TTF)2[Au(mnt)2], is obtained. However, the magnetic properties of 4 do not follow the known spin-ladder behavior owing to orientational disorder exhibited by the ETT-TTF molecules in the crystal structure. In the second approach, the acceptor complex is changed, either in the nature of the ligand or in the metal. With the [Au(i-mnt)2]– salt (i-mnt = iso-maleonitriledithiolate), the new ladder-like compound (DT-TTF)2[Au(i-mnt)2] (5), isostructural with 4, is obtained, but only as a minority product. Two other compounds with a different anion generated in situ, bearing a Au(I) dimeric core, were also isolated; (DT-TTF)9[Au2(i-mnt)2]2 (6) as the most abundant phase and (DT-TTF)2[Au2(i-mnt)2] (7) as another minority phase. Salt 7 is characterized by X-ray crystallography as a chiral compound, due to the torsion of the ligands around the central Au–Au bond. The magnetic properties of (DT-TTF)2[Au(i-mnt)2] (5) indicate that it follows a spin-ladder behavior and the electron paramagnetic resonance (EPR) data is fitted to the Troyer and Barnes and Riera equations with the parameters Δ/kB = 71 K, J∥/kB = 86 K, and J⟂/kB = 142 K, indicating a J⟂/J∥ ratio of 1.65. The change of the gold complex [Au(mnt)2] for its copper analogue, [Cu(mnt)2] also leads to a ladder-like structure, (DT-TTF)2[Cu(mnt)2] (8), which is isostructural with the gold analogue and with salts 4 and 5. The fully ionic salt (DT-TTF)[Cu(mnt)2] (9) is also obtained. The magnetic properties demonstrated that compound 8 is the third organic spin-ladder system of this family, and the values found by a fitting to the ladder equations were Δ/kB = 123 K, J∥/kB = 121 K, and J⟂/kB = 218 K, corresponding to a J⟂/J∥ ratio of 1.75, similar to that of 5 and close to that of an ideal spin ladder.

The compound NpFe4Al8 was prepared by direct arc melting of the constituent elements, followed by annealing. It crystallizes in the ThMn12-type structure (space group I4/mmm, a = 8.7480(5) A, c = 5.0372(4) A), with the iron atoms completely and only occupying the 8f positions. Magnetization measurements (T = 2–300 K, B = 0–7 T) show a ferromagnetic-type transition at TC = 135(2) K and a second anomaly at 118(3) K. The low temperature magnetization cycle is characterized by a hysteresis with a step similar to that previously observed for UFe4Al8 single crystals. First-principles density functional theory calculations of the NpFe4Al8 band structure point to a magnetic structure similar to that of UFe4Al8, in agreement with the observed magnetization cycle. The calculations indicate that the neptunium moment is aligned along one of the a or b axes, and the iron moments form a noncollinear structure in the a–b plane, with the antiferromagnetic and ferromagnetic contributions perpendicular and antiparallel to the neptunium spin moment, respectively.

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.

YFexAl12−x in the composition range 4.4⩽x⩽5 was prepared by induction melting followed by annealing in vacuum at 1270 K. Magnetization data below 150 K show complex magnetic behaviour dependent on applied field, composition and temperature. The transition temperature Tc, corresponding to the main maximum of the magnetization vs. temperature curves and below which magnetic interactions are observed for a significant fraction of the Fe atoms in the Mossbauer spectra, decreases from 180 K for x=4 down to 100 K for 4.2⩽x⩽4.7 and rises again up to 160 K for x=5. The analysis of the spectra obtained at 5 K is consistent with full occupation of the 8f sites by Fe atoms and sharing of the 8j sites by Fe and Al as deduced from the Rietveld analysis of X-ray powder diffraction data. The Mossbauer spectra further show a dependence of magnetic hyperfine fields and isomer shifts on the crystallographic site and on the number of the Fe nearest neighbours similar to that observed in UFexAl12−x (4⩽x⩽6) and RFexAl12−x (R=Y, Lu, x=4, 4.2). The magnetic properties of the UFexAl12−x and YFexAl12−x series are compared and the magnetic interactions between the different Fe sublattices are discussed.

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.

Millimetre-size UFe 5 Sn single crystals were grown by the top seed solution growth method and characterized by magnetization, 57 Fe Mossbauer spectroscopy and specific heat measurements in order to study the magnetic transitions detected in powder samples at 248 and 178 K. The magnetization measurements show different behaviour along the three crystallographic directions but with similar values of spontaneous magnetization along a and c . The transition at 248 K is associated with ferromagnetic ordering of iron moments along the c -axis, while the transition at lower temperature is associated with a reorientation towards b . Mossbauer data show that this reorientation is concomitant to the ordering of the Fe2 sites, which in a large proportion remain paramagnetic between the two transition temperatures. Specific heat measurements are consistent with the establishment of magnetic ordering at 248 K, followed by a spin reorientation at 178 K, yielding γ (0 K)≅140 mJ/(mol K 2 ) and θ ≅290 K for UFe 5 Sn.

With the aim of expanding the studies on 2D systems containing uranium, U/Co multilayers with layer thickness ranging from 50 to 200 A were recently prepared by dc magnetron sputtering onto glass. The multilayers were characterized by Grazing-Incidence X-Ray Diffraction (GIXRD) and Rutherford Backscattering Spectrometry (RBS). Magnetization measurements performed with a squid magnetometer showed that the multilayers have a ferromagnetic behaviour, with the magnetic signal increasing with the thickness of the layers. The analysis of magnetic anisotropy evidenced an easy magnetic direction in the film plane with large anisotropy fields, which increase with the thickness of the layers and suggests a positive contribution of surface anisotropy to the effective anisotropy K eff .

The copper bisdithiolene complexes based on highly extended ligands incorporating fused TTF and thiophene moieties (α-tdt = tiophenetetrathiafulvalenedithiolate and dtdt = dihydro-thiophenetetrathiafulvalenedithiolate), were prepared and characterised by cyclic voltammetry and electrical transport measurements. The anionic complexes, (nBu4N)x[Cu(dtdt)2] (1) and (nBu4N)x[Cu(α-tdt)2] (2), (1

The charge transfer salt based on the organic donor dithiophene-tetrathiafulvalene and palladium bis-maleonitrile-dithiolate, (DT-TTF)2[Pd(mnt)2], was obtained as single crystal by electrocrystallisation in dichloromethane. The crystal structure is different from the analogues previously described with other metals (Au, Cu, Ni and Pt) but of the same type as (TTDM–TTF)2[Au(mnt)2]. However in this DT-TTF salt the Pd complex is dianionic, being the donor molecules fully oxidised and the compound should then be formulated as (DT-TTF+)2[Pd(mnt)2]2–. This compound has properties of a quasi-one-dimensional semiconductor with sRT∼ 6 × 10–2 Scm–1 and Ea∼0.172 eV (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A new salt based on the [Ni(α-tpdt)2]- anion, (α-tpdt=2,3-thiophenedithiolate) and on the K+ crown-ether cation [K(18-crown-6)]+ is magnetically characterized. This salt exhibits interesting magnetic properties resulting from the spin polarization within the anionic molecule and from the specific molecular interactions arrangement in the crystal structure. Therefore the magnetic properties are due to the competition between AFM and FM interactions leading, at low temperature, to a cluster glass behaviour that is also associated with the ligand cis-trans disorder. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The conditions that allowed for the first time the growth of (Per)2[Pd(mnt)2] crystals by electrocrystallisation are described. The electrocrystallisation is limited by close proximity of the oxidation potentials of the perylene donor and [Pd(mnt)2]- anion. Depending on the experimental conditions different morphologies can be obtained. (Per)2[Pd(mnt)2] crystals were found to be mainly of the β-polymorph with properties comparable to the Cu, Ni and Pt previously described. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

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.

This article reports the investigation of a new low-dimensional organic salt, (TTDM-TTF)2 [Au(mnt)2], by single crystal X-ray diffraction, static magnetic susceptibility, EPR, thermopower, electrical resistivity measurements under pressure up to 25 kbar and band structure calculations. The crystal structure consists in a dimerized head to tail stacking of TTDM-TTF molecules separated by layers of orthogonal Au(mnt)2 anions. The absence of overlap between neighboring chains coming from this particular crystal structure leads to an extreme one-dimensionality (1-D) for which the carriers of the half-filled conduction band become strongly localized in a Mott-Hubbard insulating state. This material is the first 1-D conductor in which the Mott-Hubbard insulating character cannot be suppressed under pressure.

The nickel-borocarbides ANi 2 B 2 C [A=Y, Ln (lanthanide), An(actinide)], crystallizing in the body-centred tetragonal LuNi 2 B 2 C-type structure, are classified according to the existence or coexistence of superconducting and antiferromagnetic states (AF). The magnetic features observed in polycrystalline (A,A′)Ni 2 B 2 C solid solutions, adopting the same crystal structure, are reviewed and discussed. Published data on the magnetism in (A,Ln)Ni 2 B 2 C systems (ANi 2 B 2 C nonmagnetic, A=Y,La,Lu) indicate a gradual rise in the threshold content, x ( m ), in (Y 1− x Ln x )Ni 2 B 2 C (Ln=Gd,Tb,Dy,Ho,Er) for the establishment of AF states. (A,A′)Ni 2 B 2 C systems with magnetic end compounds show gradual variation in magnetic features when A and A′ are both heavy Ln. The behaviour of (A,A′)Ni 2 B 2 C systems of light A (Pr or U) and heavy A′ (Dy or Tm) depends on the magnetic structures of the end compounds. In intermediate compositions, incomplete moment compensation in (Pr,Dy)Ni 2 B 2 C decreases T N , while different moment directions in the end compounds in (U,Dy)Ni 2 B 2 C lead to a directional frustration of ordered moments. Such a frustration in (U,Tm)Ni 2 B 2 C is related to different magnetic structures of the end compounds.

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.[...]

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.