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Chiral bis(TTF) diamides have been obtained in good yields (54–74%) from 1,2-cyclohexane-diamine and the corresponding TTF acyl chlorides. The (R,R)-1 and (S,S)-1 enantiomers have been characterized by circular dichroism and the racemic form by single-crystal X-ray diffraction. The neutral racemic bis(TTF)-diamide shows the formation of a pincer-like framework in the solid state, thanks to the intramolecular S···S interactions. The chemical oxidation in a solution using FeCl3 provides stable oxidized species, while the electrocrystallization experiments provided radical cation salts. In particular, single-crystal resistivity measurements on the racemic donor with AsF6− as a counterion demonstrate semiconductor behavior in this material. The DFT and TD-DFT calculations support the structural and chiroptical features of these new chiral TTF donors. [ABSTRACT FROM AUTHOR]

Methyl-ethylenedithio-tetrathiafulvalene (Me-EDT-TTF (1) and dimethyl-ethylenedithiotetrathiafulvalene (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. [ABSTRACT FROM AUTHOR]

Abstract: The 1D organic salt TTF[Ni(dmit)2]2 becomes superconductor with T c=1.6K under an applied hydrostatic pressure of 7kbar. Structural determinations in this system lead us to suspect that superconductivity (SC) coexists with a charge density wave (CDW) instability at low pressure. In order to better understand how SC emerge from a CDW and to revisit the pressure–temperature phase diagram of the TTF[Ni(dmit)2]2 we performed transport and thermoelectric power measurements under pressure. [Copyright &y& Elsevier]

A chiral organic conductor with metallic conductivity has been obtained by electrocrystallisation of a diiodotetrathiafulvalene derivative and enantiopure D-camphorsulfonate anion, associated in the solid state by halogen bonding interactions. [ABSTRACT FROM AUTHOR]

Electrocrystallization of enantiopure (S,S,S,S)- and (R,R,R,R)-tetramethyl-bis(ethylenedithio)-tetrathiafulvalene (TM-BEDT-TTF) donors, as well as the racemic mixture, in the presence of potassium cations and the tris(chloranilato)ferrate(III) [Fe(Cl2An)3]3- paramagnetic anion afforded a complete series of chiral magnetic molecular conductors formulated as β-[(S,S,S,S)-TM-BEDT-TTF]3PPh4[KIFeIII(Cl2An)3]·3H2O (1), β-[(R,R,R,R)-TM-BEDT-TTF]3PPh4[KIFeIII(Cl2An)3]·3H2O (2), and β-[(rac)-TM-BEDT-TTF]3PPh4[KIFeIII(Cl2An)3]·3H2O (3). Compounds 1-3 are isostructural and crystallize in triclinic space groups (P1 for 1 and 2, P-1 for 3) showing a segregated organic-inorganic crystal structure, where anionic honeycomb layers obtained by self-assembling of the Λ and Δ enantiomers of the paramagnetic complex with potassium cations alternate with organic layers where the chiral donors are arranged in the β packing motif. Compounds 1-3 show a molecular packing strongly influenced by the topology of the inorganic layers and behave as molecular semiconductors with room-temperature conductivity values of ca. 3 × 10-4 S cm-1. The magnetic properties are dominated by the paramagnetic S = 5/2 [Fe(Cl2An)3]3- anions whose high-spin character is confirmed by magnetic susceptibility measurements. The correlation between crystal structure and conducting behavior has been studied by means of tight-binding band structure calculations which support the observed conducting properties. [ABSTRACT FROM AUTHOR]

Molecular metals have been essentially obtained with tetrathiafulvalene (TTF)-based precursors, either with multicomponent ionic materials or, in a few instances, with single-component systems. In that respect, gold bis- (dithiolene) complexes, in their neutral radical state, provide a prototype platform toward such single-component conductors. Herein we report the first single-component molecular metal under ambient pressure derived from such Au complexes without any TTF backbone. This complex exhibits a conductivity of 750 S-cm-1 at 300 K up to 3800 S-cm-1 at 4 K. First-principles electronic structure calculations show that the striking stability of the metallic state finds its origin in sizable internal electron transfer from the SOMO-1 to the SOMO of the complex as well as in substantial interstack and interlayer interactions. [ABSTRACT FROM AUTHOR]

The sensitivity of electronic propertiesof organic conductorsto minute modifications of their solid-state structure is investigatedhere within BEDT-TTF (ET) salts with organic bis-sulfonate anions,where specific hydrogen bonds between water molecules and sulfonatemoieties are shown to dynamically control the organic slabs’electronic structure. While the mixed-valence, 2,6-naphthalene-bis(sulfonate)salt, (ET)4(NBS)·4H2O, exhibitsa charge order state already at room temperature, the correspondingsalt with the 2,6-anthracene-bis(sulfonate) dianion, formulated as(ET)4(ABS)·4H2O, is metallicat RT and exhibits a metal–insulator transition at TMI= 85 K. The origin of the MI transition isrevealed from a combination of temperature-dependent spectroscopic(Raman) measurements, X-ray structure elucidations (from 300 to 15K), and theoretical investigations, demonstrating that the chargedisproportionation observed below TMIisassociated here with the progressive switching of bifurcated OH···Ohydrogen bonds between the sulfonate moieties of the anion and thetrapped water molecules. These movements within the anion layer aretransmitted through weaker C–H···O interactionsto the two A and B donor molecules, modifying the details of the overlapinteractions within AA and BB pairs and opening a gap in the bandstructure. [ABSTRACT FROM AUTHOR]

Combining recent concepts from the fields of molecular conductivity and molecular machinery we set out to design a crystalline molecular conductor that also possesses a molecular rotor. We report on the structures, electronic and physical properties, and dynamics of two solids with a common 1,4-bis(carboxyethynyl)bicyclo[2.2.2]octane (BABCO) functional rotor. One, [nBu4N+]2[BABCO][BABCO-]2, is a colorless insulator where the dicarboxylic acid cocrystallizes with two of its monoanionic conjugated bases. The other is self-assembled by electrocrystallization in the form of black, shiny needles, with highly conducting molecular slabs of (EDT-TTF-CONH2)2+ (EDT-TTF = ethylenedithiotetrathiafulvalene) and anionic [BABCO-] rotors. Using variable-temperature (5-300 K) proton spin-lattice relaxation, 1H T1-1, we were able to assign two types of Brownian rotators in [nBu4N+]2[BABCO][BABCO-]2. We showed that neutral BABCO groups have a rotational frequency of 120 GHz at 300 K with a rotational barrier of 2.03 kcal mol-1. Rotors on the BABCO- sites experience stochastic 32 GHz jumps at the same temperature over a rotational barrier of 2.72 kcal mol-1. In contrast, the BABCO- rotors within the highly conducting crystals of (EDT-TTF-CONH2)2+[BABCO-] are essentially "braked" at room temperature. Notably, these crystals possess a conductivity of 5 S cm-1 at 1 bar, which increases rapidly with pressure up to 50 S cm-1 at 11.5 kbar. Two regimes with different activation energies Ea for the resistivity (180 K above 50 and 400 K below) are observed at ambient pressure; a metallic state is stabilized at ca. 8 kbar, and an insulating ground state remains below 50 K at all pressures. We discuss two likely channels by which the motion of the rotors might become slowed down in the highly conducting solid. One is defined as a low-velocity viscous regime inherent to a noncovalent, physical coupling induced by the cooperativity between five Csp3-H⋯O hydrogen bonds engaging any rotor and five BABCO units in its environment. The rotational barrier calculated with the effect of this set of hydrogen bonds amounts to 7.3 kcal mol-1. Another is quantum dissipation, a phenomenon addressing the difference of dynamics of the rotors in the two solids with different electrical properties, by which the large number of degrees of freedom of the low dimensional electron gas may serve as a bath for the dissipation of the energy of the rotor motion, the two systems being coupled by the Coulomb interaction between the charges of the rotors (local moments and induced dipoles) and the charges of the carriers. [ABSTRACT FROM AUTHOR]

A single component molecular conductor has been isolated from electrocrystallization of the monoanionic gold bis(dithiolene) complex based on the N-ethyl-1,3-thiazoline-2-thione-4,5-dithjolate (Et-thiazdt) ligand. The crystal structure of the system exhibits layers built from parallel uniform one-dimensional stacks of the planar molecule. At room temperature and ambient pressure the system is semiconducting (0.33 Scm1) with a small activation energy. However, the single crystal conductivity is strongly pressure dependent reaching 1000 S·cm-1 at 21 kbar. At 13 kbar there is a crossover between semiconducting and metallic regimes. Thus, the present system is the first well characterized single-component molecular metal without TTF dithiolate ligands. First-principles DFT calculations show that the ground state is antiferromagnetic with a very small band gap. A simulation of the effect of pressure on the electronic structure provides a rationale for the observed variations of the conductivity and gives insight on how to further stabilize the metallic state of the system. [ABSTRACT FROM AUTHOR]