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Five new salts of 5-cyanobenzene-ethylenedithio-tetrathiafulvalene (CNB-EDT-TTF), with the general formula (CNB-EDT-TTF)4A, and anions A = Ag(CN)2 (1), Ag(CN)2·H2O (2), Ag2(CN)3 (3), Ag(SCN)2 (4) and Hg2(SCN)5 (5), were prepared by electrocrystallisation and characterised by single crystal X-ray diffraction, electrical conductivity, thermoelectric power and magnetic susceptibility measurements. Their crystal structure is based on a double layer arrangement of the donors with a β′′ packing pattern identical to that previously observed in related salts with small discrete anions. The donor bilayers are separated by layers of anions which however are incoherently arranged perpendicular to the layers. The average structures obtained are compatible with anionic arrangements similar to those previously observed in single layer salts of BEDT-TTF and related donors, where, with the exception of 1, the anions are polymeric. While 2 presents electrical resistivity with a thermally activated regime, 1, 3, 4 and 5 show metallic behaviour at high temperatures, with room temperature values in the range 10–20 S cm−1 and sample dependent electronic localisation effects at lower temperatures. The thermoelectric power of these compounds is +82–90 μV K−1 at room temperature, following behavior identical to that of their analogues with small discrete anions. The paramagnetic susceptibility of 4 and 5, similar to those of their analogues with I3, PF6, AsF6 and ReO4 anions, has values of ≈1.0 × 10−3 emu mol−1 at room temperature, being significantly enhanced compared with the Pauli-type contribution predicted from electron band calculations. [ABSTRACT FROM AUTHOR]

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 C≡N⋯H–C interactions, which can be described as an effective combination of R 22 (10) and R 24 (10) synthons, forming donor bilayers alternating with anionic layers. The magnitude of the interactions associated with R 22 (10) and R 24 (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 Å). 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. [ABSTRACT FROM AUTHOR]

Three salts of the dissymmetrical TTF derivative cyanobenzene-ethylenedithio-tetrathiafulvalene (CNB-EDT-TTF) with different anions, namely, (CNB-EDT-TTF)2[M(mnt)2] [M = Ni ( 1), Au ( 2); mnt = maleonitriledithiolate] and (CNB-EDT-TTF)FeBr4 ( 3) were prepared and characterized by single-crystal X-ray diffraction, magnetic susceptibility, and electrical conductivity measurements. Compounds 1 and 2 are isostructural with a crystal structure characterized by segregated chains of side-by-side donor dimers and acceptors, and compound 3 presents donors in dimerized stacks. In spite of the different structural types and stoichiometries, all of these compounds have C-N ···H pairing interactions associated with R22(10) synthons between donors in nearby chains. All compounds are poor semiconductors, and the magnetic susceptibility of 1 is dominated by the contribution of the paramagnetic [Ni(mnt)2] anions with small antiferromagnetic interactions. The magnetic susceptibility of 3 is dominated by the paramagnetic FeBr4 anions and follows a Curie-Weiss law with a Weiss temperature θ = -19 K, which denotes significant antiferromagnetic interactions that are most likely mediated by the donors. [ABSTRACT FROM AUTHOR]

(α-DT-TTF)2[Au(i-mnt)2] and (α-DT-TTF)2[Co(mnt)2] are two new salts of the donor α-dithiophene-tetrathiafulvalene with stable diamagnetic anions, both presenting a ladder structure of the donors organized in paired segregated stacks. The first one is isostructural with previously reported closely related compounds and presents a magnetic spin-ladder behavior with J∥= 83.5 K and J⊥ = 110.3 K as estimated from spin susceptibility data in single crystals. (α-DT-TTF)2[Co(mnt)2] presents a new structural type with a different arrangement of pairs of donor stacks, alternating with stacks of dimerized [Co(mnt)2] anions which are however arranged in an uncorrelated fashion perpendicular to the stacking axis. Due to the strong coupling between the disordered anion chains and the donor chains, this compound does not present a magnetic spin-ladder behavior. The low temperature superstructure of (DT-TTF)2[Cu(mnt)2] below the transition at 235 K, previously known to be associated with a lattice doubling along the stacking axis, was solved by synchrotron radiation diffraction in small single crystals. It is found that this dimerization is due to donor charge localization with the spin carriers being associated with fully oxidized donor species alternating with neutral donors. [ABSTRACT FROM AUTHOR]

A new pyridine-substituted dithiolene complex, PPh4[Au( 4-pdddt)2] ( 3), was prepared and characterised. Cyclic voltammetry shows three redox processes corresponding to the interconversion between dianionic, monoanionic, neutral and cationic states, as often presented by this type of bis(dithiolene) complexes. However, the last oxidation process in this compound leads to a polymerised species obtained as an electrodeposited film. By potentiostatic electrodeposition, thin films of either the neutral gold complex, [Au( 4-pdddt)2] ( 4), or the polymerised cationic species can be obtained. Both films absorb strongly in the NIR region and have properties consistent with the incorporation of the intact metal bis(dithiolene) complex. A mechanism for polymerisation through formation of S-S interligand bonds is proposed. [ABSTRACT FROM AUTHOR]

The crystal structure of (Per)2[Co(mnt)2], was investigated by single crystal X-ray diffraction. Its refinement shows a strong chemical dimerization of the anions [Co(mnt)2]22−. This is responsible for a unit cell doubling along the staking axis bwhen compared with other members of the α-(Per)2[M(mnt)2] family of the low dimensional molecular conductors, with M = Ni, Cu, Au, Pt or Pd. The dimerized [Co(mnt)2]22−stacks appear however as poorly correlated in the acplane. The electrical conductivity of this compound measured in single crystals exhibits anomalous pressure dependence, where under increasing hydrostatic pressure the conductivity decreases while the metal insulator transition temperature is enhanced. This effect is ascribed to the dimeric nature of the counterions which imposes a sliding of the stacked perylene molecules along alternated directions in their planes. [ABSTRACT FROM AUTHOR]

The electrocrystallization from solutions of cyanobenzene-ethylenedithio-tetrathiafulvalene (CNB-EDT-TTF) in the presence of different anions X = ClO4-, PF6-, and I3-, affords a new type of 2D molecular metals with composition (CNB-EDT-TTF)4X based on an unprecedented bilayer structure of the donors induced by effective head to head interdonor interactions through the nitrile groups, which is responsible for 2D metallic systems with unusual properties such as the higher band filling, larger effective mass of carriers, and almost degenerated double Fermi surfaces. [ABSTRACT FROM AUTHOR]

The synthesis of the [Fe(5-Cl-qsal) 2 ][Ni(dmit) 2 ]·2CH 3 CN ( 1 ) is reported in the present work. The crystal structures of 1 , solved at 150, 245, 255 and 294 K, revealed the presence of low spin (LS) and high spin (HS) Fe III centers at 150 and 294 K, respectively, and mixed HS/LS states ∼50:50 and 75:25 at 245 and 255 K. The crystal structure is based on alternating cationic and anionic layers, where each layer is composed of an arrangement of chains of cations or anions. The anionic chains consist on the stacking of face-to-face pairs of [Ni(dmit) 2 ] − anions. Extended ππ contacts, involving the 5-Cl-qsal ligands, were observed in the cationic chains. The contribution of the anions to the magnetization correlates well with an alternating chain, dominated by antiferromagnetic interactions. A spin crossover (SCO) process, assigned to the [Fe(5-Cl-qsal) 2 ] + cationic network was observed at high temperatures ( T ∼ 240 K). The thermal dependence of the magnetization suggests the existence of an abrupt change at ∼233 K from the LS state to a mixed 50:50 HS/LS state, followed by a gradual transformation at ∼256 K to the HS state. A structural transformation consisting of the doubling of the unit cell was observed to be associated with the SCO process. [ABSTRACT FROM AUTHOR]