Radical Cation Salts Research Articles

Chiral EDT-TTF precursors with one stereogenic centre: substituent size modulation of the conducting properties in the (R-EDT-TTF)2PF6 (R = Me or Et) series

The first enantiopure monoalkylated EDT-TTF derivatives provided mixed-valence chiral radical cation salts showing metallic or semiconducting character.

Structural relations in (1 : 1) and (2 : 1) cyanobenzene-ethylenedithio-TTF radical salts; the role of CN⋯H interactions

Radical cation salts of 4-CNB-EDT-TTF presenting CN⋯H pairing interactions, semiconducting properties and chains of antiferromagnetically coupled donor dimers.

A 4-cyanobenzene-ethylenedithio-TTF electron donor and its (1 : 1) triiodide radical cation salt; isomer effects in C–N⋯H–C interactions

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.

Preparation and Properties of a Polycyclic p-Quinodimethane with Two Oxygen Bridges and its Radical Cation in Comparison with the Isomeric o-Quinodimethane.

We prepared an electron-rich p-quinodimethane compound, 2,9-dibromo-7,14-dimesityl-5,12-dioxapentacene (1). The quinoidal character was clarified by bond-length alternation in the central ring. Clear vibrational structures in both absorption and emission bands and small Stokes shift indicate the rigid dioxapentacene framework. The reversible redox waves of 1 were observed at +0.14 and +0.69 V vs. Fc+ /Fc, respectively. The radical cation salt 1⋅+ ⋅SbF6 - was successfully isolated and characterized by means of X-ray structural analysis and ESR and UV/Vis-near infrared absorption spectroscopies. The molecular structure and electronic properties of the neutral and radical cation species were compared to those of the isomeric o-quinodimethane.

Large magnetic anisotropy of chromium(III) ions in a bis(ethylenedithio)tetrathiafulvalenium salt of chromium bis(dicarbollide), (ET)2[3,3′-Cr(1,2-C2B9H11)2

The synthesis of a radical-cation salt based on a derivative of tetrathiafulvalene, (ET)2[3,3′-Cr(1,2-C2B9H11)2] (ET = bis(ethylenedithio)tetrathiafulvalenium), was accomplished by electrochemical anodic oxidation of ET in the presence of (Me4N)[3,3´-Cr(1,2-C2B9H11)2] in the galvanostatic regime. An electric conductivity σ (293 K) = 7 × 10−3 Ohm−1 cm−1 with semiconductor activation energy Ea ≅ 0.1 eV in the range of 127–300 K was observed. The crystal structure of (ET)2[3,3′-Cr(1,2-C2B9H11)2] was determined by X-ray diffraction at 173 K, revealing the presence of structural tetramers in radical-cation stacks. The magnetic properties of the complex were investigated in the temperature range 1.8–300 K using magnetometry and EPR, showing that the magnetic structure of (ET)2[3,3′-Cr(1,2-C2B9H11)2] consists of two independent magnetic subsystems. Cation radicals form a rectangular magnetic lattice in the ab-plane with significant antiferromagnetic exchange interactions. The chromium bis(dicarbollide) anions are characterized by unusually strong positive zero-field splitting of the Cr(III) ions, which was confirmed by ab initio calculations.

Decoupling anion-ordering and spin-Peierls transitions in a strongly one-dimensional organic conductor with a chessboard structure, (o-Me2TTF)2NO3.

A mixed-valence conducting cation radical salt of the unsymmetrically substituted o-Me2TTF donor molecule (TTF is tetrathiafulvalene) was obtained upon electrocrystallization in the presence of the non-centrosymmetric NO3- anion. It crystallizes at room temperature in the monoclinic P21/c space group, with the anion disordered on an inversion centre. The donor molecules are stacked along the a axis. A 90° rotation of the longest molecular axis of o-Me2TTF generates a chessboard-like structure, preventing lateral S⋯S contacts between stacks and providing a strongly one-dimensional electronic system, as confirmed by overlap interaction energies and band structure calculations. A strong dimerization within the stacks explains the semi-conducting behaviour of the salt, with σroom temp = 3-5 S cm-1 and Eactivated = 0.12-0.14 eV. An X-ray diffuse scattering survey of reciprocal space, combined with full structure resolutions at low temperatures (250, 85 and 20 K), evidenced the succession of two structural transitions: a ferroelastic one with an anion-ordering (AO) process and the establishment of a (0, ½, ½) superstructure below 124 (±3) K, also visible via resistivity thermal dependence, followed by a stack tetramerization with the establishment of a (½, ½, ½) superstructure below 90 (±5) K. The latter ground state is driven by a spin-Peierls (SP) instability, as demonstrated by the temperature dependence of the magnetic susceptibility. Surprisingly, these two kinds of instability appear to be fully decoupled here, at variance with other tetra-methyl-tetra-thia-fulvalene (TMTTF) or tetramethyl-tetra-selena-fulvalene (TMTSF) salts with such non-centrosymmetric counter-ions.

Specific Structural Disorder in an Anion Layer and Its Influence on Conducting Properties of New Crystals of the (BEDT-TTF)4A+[M3+(ox)3]G Family, Where G Is 2-Halopyridine; M Is Cr, Ga; A+ Is [K0.8(H3O)0.2

New crystals (1–4) of organic conductors based on the radical cation salts of the bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) with paramagnetic and diamagnetic tris(oxalato)metallate anions {A+[M3+(ox)3]3−G}2−, where M is Cr, Ga; G is 2-chloropyridine, 2-bromopyridine; and A+ is [K0.8(H3O)0.2]+ have been prepared and their crystal structure and transport properties were studied. All crystals belong to the monoclinic group of the (BEDT-TTF)4A+[M3+(ox)3]G family with β″-packing type of conducting BEDT-TTF layers. In contrast to the known superconducting crystals with M3+ = Fe3+ and G = 2-chloro- or 2-bromopyridine (Tc = 4.0–4.3 K), crystals with Cr3+ and Ga3+ ions exhibit metallic properties down to 0.5 K without superconducting transition. Upon cooling these crystals, the incommensurate superstructure appears, which has never been observed before in the numerous β″-salts of the family. In addition, orthorhombic (sp. group Pbca) semiconducting crystals α″-(BEDT-TTF)5[Ga(ox)3]·3.4·H2O·0.6 EtOH (5) were obtained. It is a new compound in the family of BEDT-TTF crystals with tris(oxalato)metallate anions.

Crystal structure and physical properties of radical cation salt based on 4,5-ethylenedioxy-4′-iodotetrathiafulvalene (EDO-TTF-I) with iodine bonding ability

The radical cation salt of 4,5-ethylenedioxy-4′-iodotetrathiafulvalene possessing iodine bonding ability afforded the β′-type molecular arrangement in dimerized Mott insulating state.

Synthesis of Quinoline Derivatives Containing Lactone Structure Promoted by Radical Cation Salt

Synthesis of Quinoline Derivatives Containing Lactone Structure Promoted by Radical Cation Salt

СИНТЕЗ ОКИСНЕНОЇ ФОРМИ ДИТІЄНО-ТТФ МЕТОДОМ ЕЛЕКТРОКРИСТАЛІЗАЦІЇ

General principles of the electrocrystallization technique in application to organic molecules are shown, as some historical background. Based on this, we were able to rationalize main variables in the experiment which are needed in order to get crystals of the oxidized form, that are suitable for further applications such as for example single crystal x-ray diffraction analysis or conductivity measurements. The biggest impact comes from such factors as choice of solvent and supporting electrolyte, which influence directly the solubility of both the starting compound and its oxidized form. Purity of all components is also paramount. In order to avoid formation of by-products, experiment is usually performed in a sealed U-shaped electrochemical cell with a glass filter between the anodic and cathodic compartments and under inert atmosphere such as argon or nitrogen. Other parameters considered here, such as temperature of the solution and intensity of the current, help to fine-tune the result, but have less impact on whether the crystallization will occur at all. It is also critical to maintain both parameters at constant values in order to obtain high quality single crystals. Galvanostatic oxidation mode is more favourable comparing to the potentiostatic as it allows steady rate of oxidation by providing fixed intensity of the electrical current and subsequently more stable rate of crystal grows, although potentiostatic mode or alternating current can be used to grow bigger amounts when quality of the single crystal is less important. Further we used this approach to electrocrystalize previously obtained by our group dithieno-TTF, based on the exTTF scaffold. According to the literature cyclic voltammetry data, dithieno-TTF undergoes reversible single-wave two electron oxidation to form bis-cation similar to classic exTTF, but in our case only radical-cation salt was obtained in a form of shiny, dark-red, needle-like single crystals. This could be attributed to its extremely low solubility and corresponding formation of the kinetic product, which correlate well with relatively fast crystallization just within 3 days. Another possibility is a comproportionation reaction involving the starting neutral molecule and oxidized dication.

Recent Progress in Radical Cation Salts Promoted Chemical Transformations

Recent Progress in Radical Cation Salts Promoted Chemical Transformations

Syntheses, structures and theoretical calculations of stable triarylarsine radical cations.

The first stable triarylarsine radical cation salts 1˙+[BArF4]- and 2˙+[BArF4]- were afforded by one-electron oxidation of triarylarsines Trip3As (1, Trip = 2,4,6-iPr3C6H2) and Dipp3As (2, Dipp = 2,6-iPr2C6H3) with AgSbF6 and NaBArF4 (ArF = 3,5-(CF3)2C6H3), respectively. Their molecular and electronic structures were investigated by single-crystal X-ray diffraction, electron paramagnetic resonance (EPR) and UV-vis absorption spectroscopy, in conjunction with density functional theory (DFT) calculations. The EPR and computational results demonstrate that the spin density of 1˙+ and 2˙+ is mainly distributed on the As nuclei.

Synthesis and Physical Properties of Purely Organic BEDT-TTF-Based Conductors Containing Hetero-/Homosubstituted Cl/CN-Anilate Derivatives.

Radical cation salts composed of a bis(ethylenedithio)tetrathiafulvalene (ET) donor with homo-/heterosubstituted Cl/CN anilic acids as purely organic molecular conducting materials formulated as [BEDT-TTF]2[HClCNAn] (1) and [BEDT-TTF][HCl2An] (2) have been prepared by electrocrystallization. Compounds 1 and 2 crystallized in the monoclinic space group P2/c for 1 and I2/a for 2, showing segregated donor-anion layers arranged in a α'-type donor packing pattern (1) and twisted parallel columns (2), respectively. Single-crystal conductivity measurements show that 1 is a semiconductor with room-temperature conductivity of 10-2 S cm-1 and an activation energy Ea of 1900 K.

Back Cover: Facile Construction of Quinoline‐2‐carboxylate Esters through Aerobic Oxidation of Alkyl 4‐Anilinocrotonates Induced by a Radical Cation Salt (Chem. Asian J. 14/2017)

Back Cover: Facile Construction of Quinoline‐2‐carboxylate Esters through Aerobic Oxidation of Alkyl 4‐Anilinocrotonates Induced by a Radical Cation Salt (Chem. Asian J. 14/2017)

Facile Construction of Quinoline-2-carboxylate Esters through Aerobic Oxidation of Alkyl 4-Anilinocrotonates Induced by a Radical Cation Salt.

A facile construction of quinoline-2-carboxylate esters through an aerobic oxidation of alkyl 4-anilinocrotonates is described. In the presence of dioxygen, sp3 C-H bonds in 4-anilinocrotonates can easily be oxidized by using a catalytic amount of a radical cation salt, providing a radical intermediate. After further oxidation and domino cyclization, the desired quinoline derivatives were afforded in high yields. This reaction provides a new way to construct the pharmaceutically relevant quinoline skeleton, avoiding harsh reaction conditions and tedious starting material synthesis.

Tetrathiafulvalene based electroactive ligands and complexes: Synthesis, crystal structures and antifungal activity

The synthesis of two tetrathiafulvalene-appended pyridinehydrazone pyrimidine ligands, namely (Z)-4-(2-((5-([2,2′-bi(1,3-dithiolylidene)]-4-yl)pyridin-2-yl)methylene) hydrazinyl)-6-chloropyrimidine L1 and (Z)-4-(2-((6-([2,2′-bi(1,3-dithiolylidene)]-4-yl)pyridin-2-yl)methylene) hydrazinyl)-6-chloropyrimidine L2 is described. Ligand L1 was reacted with cobalt(II) to yield a cationic metal complex [Co(L1)2] while ligand L2 was reacted with zinc(II) to afford a neutral metal complex [ZnL2Cl2]. The crystal structure analysis of [Co(L1)2] indicate that Co(II) ion is coordinated by six nitrogen atoms from two perpendicular ligands while in [ZnL2Cl2], Zn(II) is coordinated by two chlorine atoms and three nitrogen atoms. The electrochemical behavior indicate that ligands L1 and L2 and the zinc(II) complex are suitable fort the preparation of crystalline radical cation salts. Finally the determination of MIC80 values against C. albicans, C. glabrata, C. parapsilosis, C. krusei and E. dermatitidis revealed that the cobalt(II) metal complex [Co(L1)2] is active against all the studied fungi.

New radical cation salt κ-(BETS)2Co0.13Mn0.87[N(CN)2]3 with two magnetic metals: Synthesis, structure, conductivity and magnetic peculiarities

A new metallic radical cation salt κ‐(BETS)2Co0.13Mn0.87[N(CN)2]3, where BETS is bis(ethylenedithio)tetraselenafulvalene, C10S4Se4H8, has been synthesized. In this salt, a part of Mn2+ ions are replaced by Co2+ which acts as a magnetic dopant with a different effective magnetic moment. Crystal structure, band structure, conducting and magnetic properties of the salt have been studied. Below 30K the material undergoes a metal-insulator transition, which is suppressed by applying a pressure of ∼0.5 kbar, leading to a superconducting ground state. While the structural and conducting properties are very similar to those of the parent salt κ‐(BETS)2Mn[N(CN)2]3, magnetic properties associated with localized moments in the anion layer are found to be surprisingly different.

First hybrid radical-cation salts with halogen substituted iron bis(dicarbollide) anions – synthesis, structure, properties

New radical-cation salts based on bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF or ET) were synthesized: (ЕТ)2[8,8′-Br2-3,3′-Fe(1,2-C2B9H10)2] (1) and (ЕТ)[8,8′-I2-3,3′-Fe(1,2-C2B9H10)2] (2). Their crystal structures were studied by X-ray analysis, electroconducting and magnetic properties were measured in a wide temperature range. Salts (1) and (2) appeared to be the first radical-cation salts with [8,8′-I2-3,3′-Fe(1,2-C2B9H10)2]- and [8,8′-Br2-3,3′-Fe(1,2-C2B9H10)2]- anions, respectively. In the literature [8,8′-I2-3,3′-Fe(1,2-C2B9H10)2]- and [8,8′-Br2-3,3′-Fe(1,2-C2B9H10)2]- anions are presented for the first time. Salts (1) and (2) were found to be paramagnetic. Their room temperature conductivities were 2 and 1·10−6 Ohm−1cm−1, respectively.

New Ethylenedithio-TTF Containing a 2,2,5,5-Tetramethylpyrrolin-1-yloxyl Radical through a Vinylene Spacer and Its FeCl4− Salt—Synthesis, Physical Properties and Crystal Structure Analyses

To develop novel magnetic conductors exhibiting conducting/magnetic bifunctionalities and peculiar responses to applied magnetic fields, we synthesized new EDT-TTF (ethylenedithiotetrathiafulvalene) donor containing a 2,2,5,5-tetramethylpyrrolin-1-yloxyl radical through a π-conjugated vinylene spacer 1 and examined its electronic and crystal structures, and physical properties. We also prepared its cation radical salts by an electrochemical oxidation method and successfully cleared the crystal structures and magnetic properties of the cation radical salts, 1·FeCl4 and 1·GaCl4. These salts have strongly dimerized one-dimensional arrays of the fully oxidized donor molecules, giving rise to the formation of spin-singlet state of the π cation radical spins in the dimer. On the other hand, the FeCl4- anion locates on the side of the dimers with very short S-Cl contacts and mediates very strong π-d interaction between the donor and anion moieties, resulting in the antiferromagnetic behavior of the Weiss temperature of θ = -3.9 K through its d-π-d interaction.

Enantiopure and racemic radical-cation salts of bis(2'-hydroxylpropylthio)(ethylenedithio)TTF with polyiodide anions.

The chiral TTF-based donor molecule bis(2'-hydroxylpropylthio)(ethylenedithio)tetrathiafulvalene (BHPT-EDT-TTF) has produced enantiopure R,R and S,S radical-cation salts with polyiodide anions I3- and I82-. Enantiomorphic 6 : 6 donor : I3 phases grown from either the R,R or S,S donor are semiconducting with similar activation energies of 0.24-0.30 eV and 0.22-0.23 eV, respectively, and contain three unique face-to-face donor pairs whose relative orientation is determined by side chain conformations and hydrogen bonding. Racemic material under the same conditions gave an insulating centrosymmetric phase with R,R and S,S donor cations in a face-to-face pair partnered with an octaiodide dianion, and with a ca. 3 : 1 disorder between the enantiomers. Enantiopure BHPT-EDT-TTF yielded two further insulating crystalline phases of composition 2 : 2 with triiodide and 2 : 1 with octaiodide.