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Within this work we have investigated spiro‐based tetrathiafulvalenes (TTFs) obtained as mixtures of stereoisomers from racemic spiro[5.5]undeca‐1,8‐dien‐3‐one. Compared to previously described spiro‐TTFs, enantiomeric and diastereoisomeric forms have been here separated by chiral HPLC and fully characterized both experimentally and theoretically. The two types of spiro‐based chiral derivatives contain either one (2) or three (1) chiral centres out of each one is spiro‐type. Experimental CD, supported by TD‐DFT calculations, shows differences in the optical activity between the 1 and 2 and their intermediates. The low optical activity of 2 and 3 (spiro alone chirality) was attributed to the presence of two conformers in the solution (ax and eq) of opposite Cotton effect whereas in the case of 1 and 5 (spiro and stereogenic centres) the spiro chirality seems to be responsible of the Cotton effect in the high energy region whereas the R and S chirality in the low energy region. Racemic and enantiopure forms have been successfully used for the synthesis of charge transfer complexes with tetracyanoquinodimethane (TCNQ) based acceptors. [ABSTRACT FROM AUTHOR]

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]

Control of the structural type in metallic enantiopure and racemic radical cation salts is achieved through hydrogen bonding interactions between the chiral donor DM-EDT-TTF and the XF6 anions (X = P, As, Sb), determined by the anion size and the chiral information. [ABSTRACT FROM AUTHOR]

The enantiopure radical cation salts [( S, S)-DM-BEDT-TTF]4[ReCl6] ([( S, S)- 1]4[ReCl6]) and [( R, R)-DM-BEDT-TTF]4[ReCl6] ([( R, R)- 1]4[ReCl6]) [DM-BEDT-TTF = dimethylbis(ethylenedithio)tetrathiafulvalene] have been prepared by electrocrystallization of the chiral precursor DM-BEDT-TTF in the presence of NBu4[ReCl5(pyrazine)] (NBu4 = tetra- n-butylammonium cation; pyz = pyrazine) as supporting electrolyte. The single-crystal X-ray analysis shows that the compounds crystallize in the triclinic system, non-centrosymmetric space group P1, and that the donors arrange in parallel columns. The four independent donor molecules possess approximate charges of +1, +1/2, +1/2 and 0, according to the structural parameter analysis and band-structure calculations, which also support the semiconducting behaviour of the materials. The rhenium(IV) ion in both compounds is six-coordinate with six chloro atoms that describe a slightly distorted octahedral environment with Re-Cl distances that cover the short range 2.348-2.374 Å. Magnetic measurements on polycrystalline samples of [( S, S)- 1]4[ReCl6] and [( R, R)- 1]4[ReCl6] have been investigated in the temperature range 2-295 K. They are practically identical and confirm the presence of high-spin S = 3/2 [ReCl6]2- isolated monomers together with a Pauli paramagnetism, typical of this kind of system. The magnetic susceptibility data are thoroughly reproduced over the whole temperature range with a simple model of isolated S = 3/2 ions with a zero-field splitting plus a temperature-independent paramagnetism (TIP), and the best-fit parameters being gRe = 1.875(2), | D| = 4.50(3) cm-1 and TIP = 3630(20)×10-6 cm3 mol-1 (2 D is the energy gap between the MS = ±3/2 and MS = ±1/2 Kramers doublets). [ABSTRACT FROM AUTHOR]

Enantiopure (S,S) and (R,R) dimethyl-ethylenedithio-tetrathiafulvalene (DM-EDT-TTF) 1 donors are synthesized by cross coupling followed by decarboxylation reactions. In the solid state the methyl groups are arranged in axial positions within sofa-type conformation for the six-membered rings. Crystalline radical cation salts formulated as [(S,S)-1]2PF6, [(R,R)-1]2PF6, and [(rac)-1]2PF6 are obtained by electrocrystallization. When the experiment is conducted with enantioenriched mixtures both enantiopure and racemic phases are obtained. The monoclinic enantiopure salts, containing four independent donors in the unit cell, show semiconducting behavior supported by band structure calculations of extended Hückel type. The racemic salt contains only one independent donor in the mixed valence oxidation state +0.5. Under ambient pressure the racemic material is metallic down to 120 K, while an applied pressure of 11.5 kbar completely suppresses the metal-insulator transition. Band structure calculations yield an open Fermi surface, typical for a pseudo-one-dimensional metal, with unperfected nesting, thus ruling out the possibility of charge or spin density modulations to be at the origin of the transition. Raman spectroscopy measurements, in agreement with structural analysis at 100 K, show no indication of low-temperature charge ordering in the racemic material at ambient pressure, thus suggesting Mott-type charge localization for the observed metal-insulator transition. [ABSTRACT FROM AUTHOR]

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]

Conducting and chira] [Ni(dmit)2] dithiolene salts were obtained by electrocrystallization of the radical [n-BU4N] [Ni(dmit)2] salt in the presence of chiral, enantiopure trimethylaiumonium cations. Three different cations were investigated, namely, (R)-Ph(Me)HC*-NMe3*, (S)-('Bu)- (Me)HC*-NMe3+, and (S)-(1-Napht)MeHC*-NMe3*, noted (R)-l, (S)-2, and (S)-3. Salts of 1:3 stoichiometry were obtained with (R)-l and (S)-2, formulated as [(R)-1] [Ni(dmit)2]3 and [(S)-2][Ni(dmit)2]3-(CH;,CN)2, They both crystallize in the P2i2j2i chiral space gi'oup, with three crystallographically independent complexes exhibiting different oxidation degrees. Another salt with 2:5 stoichiometry was isolated with (S)-3. The semiconducting character of the three salts (σRT - 20--30 X 10-3 S cm-1) finds its origin in a stiong electron localization, favored by the large number of crystallographically independent [Ni(dmit)2] complexes in these chiral structures and their association into wealdy interacting dimeric or trimeric motifs. Racemic salts with the same cations, obtained only with difficulties witli the íerí-butyl-containing (rac)-2 cation, afforded similar trimerized structures. The observed unusual stoicliiometry and stiong charge localization is tentatively assigned to the size and anisotiopic charge distribution of the cations. [ABSTRACT FROM AUTHOR]

The article discusses the syntheses, structure and properties of chiral molecular metals. Within the extended series of organic metals and superconductors based on tetrathiafulvalene (TTF) and derivatives, the introduction of chirality offers an invaluable opportunity to evaluate the role of disorder on the conductive properties since radical cation salts of enantiopure donors are expected to suffer less from structural disorder than those of racemates, where the crystal structure may tolerate the enantiomers exchanging places.