ET Molecules Research Articles

Electron Localization Induced by Disordered Anions in an Organic Conductor.

We report on a new organic conductor κ″-(ET)2Cu[N(CN)2]Br (κ″-Br), which is the first polymorph of an organic superconductor κ-(ET)2Cu[N(CN)2]Br (κ-Br), where ET denotes bis(ethylenedithio)tetrathiafulvalene. κ″-Br has a similar κ-type arrangement of ET molecules to κ-Br, but, in contrast to the orthorhombic κ-Br, which has ordered polyanion chains, presents a monoclinic crystal structure with disordered polymeric anion chains. To elucidate the electronic state of κ″-Br, we performed band calculations as well as transport, magnetic, and optical measurements. The calculated band dispersion, magnitude of electron correlation, and room-temperature optical conductivity spectra of κ″-Br were comparable to those of κ-Br. Despite these similarities, the κ″-Br salt exhibited a semiconducting behavior. The electron spin resonance and Raman spectroscopies indicated that there is neither magnetic nor charge order in κ″-Br, suggesting the occurrence of Anderson localization due to disordered anion layers.

High pressure investigation of an organic three-dimensional Dirac semimetal candidate having a diamond lattice

$(\mathrm{ET}){\mathrm{Ag}}_{4}{(\mathrm{CN})}_{5}$ [ET = BEDT-TTF: bis(ethylenedithio)tetrathiafulvalene] is a rare example of organic conductors that crystallizes in a diamond structure due to the tetrahedral arrangement of neighboring ET molecules. Because each ET has a $+1$ site charge, the band is half filled, which in combination with strong Coulomb interactions, turn $(\mathrm{ET}){\mathrm{Ag}}_{4}{(\mathrm{CN})}_{5}$ into a Mott insulator. Recently, it was realized that this material may realize a nodal Dirac semimetal with a diamondlike lattice, whose state can be induced by suppressing the strong electron correlations. In this report, we present high pressure transport and optical studies on $(\mathrm{ET}){\mathrm{Ag}}_{4}{(\mathrm{CN})}_{5}$. Our transport study indicates that the activation energy is highly suppressed by the application of hydrostatic pressure. At high pressures, the system varies from activated behavior into Coulomb gap variable range hopping.

Коррелятивные взаимосвязи между показателями системной эндотоксинемии и липидного профиля у пациентов без клинических проявлений атеросклероза

Актуальность. Атеросклероз является проявлением хронического системного воспаления, индукция которого может быть связана с эндотоксиновой агрессией (ЭА), как патогенной формы системной эндотоксинемии (СЭЕ). Цель: выявить коррелятивные связи между показателями липидного профиля и СЭЕ в зависимости от степени выраженности атеросклеротического процесса. Материалы и методы. Проводился опрос пациентов с использованием шкалы оценки риска SCORE. Всем выполнялось триплексное ультразвуковое исследование экстракраниального отдела брахиоцефальных артерий на аппарате Medison SA9900 (Южная Корея) с оценкой структуры и толщины комплекса интима-медиа (ТИМ), расчёта степени стенозирония методом ECST. Оценивались параметры липидного профиля (общий холестерин (ОХС), ЛПНП, ЛПВП, ТГ, индекс атерогенности (ИА)) и показатели СЭЕ: методом микро-ЛАЛ-теста концентрация липополисахарида (ЛПС) и активность АЭИ при помощи СОИС-ИФА. Результаты. С использованием шкалы SCORE пациенты были отнесены к средней группе риска по развитию сердечно-сосудистых осложнений. На основании данных УЗИ пациенты были разделены на три подгруппы. Первая: утолщение ТИМ; вторая: с атеросклеротическими бляшками; третья: без признаков нарушения структуры стенки артерии, но с нарушенными параметрами липидного профиля. Нами не было выявлено статистически значимых различий между подгруппами по параметрам липидного профиля, но пациенты значимо отличались от группы контроля по концентрации ЛПНП, ОХС и ИА. Не было статистически значимых различий по параметрам СЭЕ между обследуемыми в подгруппах и группой контроля. Однако множественная регрессия показала значительное влияние уровня ЭТ и соотношения антител к гидрофильной/гидрофобной частям молекулы ЛПС на уровень ОХС и ИА (p < 0,001). Заключение. Обнаруженная нами прямая взаимосвязь между показателями концентрации ЛПС в общем кровотоке и ОХС может быть следствием более высокого сродства молекулы ЭТ к ЛПВП и конкурентным связываем при транспорте молекул. Это дает возможность объяснить обнаруженные прямые коррелятивные взаимосвязи параметров СЭЕ и липидного профиля. Background. Atherosclerosis is a manifestation of chronic systemic inflammation, the induction of which may be associated with endotoxin aggression (EA) as a pathogenic form of systemic endotoxemia (SEE). Objective: to identify correlations of the lipid profile with SEE depending on severity of the atherosclerotic process. Materials and methods. Patients were interviewed using the SCORE risk assessment scale. All patients underwent a triplex ultrasound examination of extracranial brachiocephalic arteries using Medison SA9900 (South Korea) including evaluation of the intima-media complex (TIM) structure and thickness. The ECST method was used to quantify arterial stenosis. Indices of the lipid profile (total cholesterol, LDL, HDL, TG, atherogenic index (AI)) and SEE were estimated; the micro-LAL test was used to measure the lipopolysaccharide (LPS) concentration; and the AEI activity was measured using SOIS-ELISA. Results. Using the SCORE scale patients were assigned to the group of intermediate risk for development of cardiovascular complications. Based on ultrasound data the patients were divided into three subgroups: first subgroup, TIM thickening; second subgroup, atherosclerotic plaques; third subgroup, no signs of disturbed structure of the arterial wall but abnormal lipid profile. There were no significant differences between subgroups in indices of the lipid profile but patients significantly differed from the control group in concentrations of LDL, cholesterol, and AI. Statistically significant differences in SEE indices between the subgroups and the control group were absent. However, multiple regression showed a significant effect of the ET level and the ratio of antibodies to the hydrophilic/hydrophobic parts of the LPS molecule on the level of total cholesterol and AI (p < 0.001). Conclusion. The observed direct relationship between concentrations of LPS in the systemic circulation and total cholesterol may be due to a higher affinity of the ET molecule to HDL and the competitive binding in transport of molecules. This explains the found direct correlations of SEE indices with the lipid profile.

Mn‐Containing Paramagnetic Conductors with Bis(ethylenedithio)tetrathiafulvalene (BEDT‐TTF)

Two novel paramagnetic conductors have been prepared with the organic donor bis(ethylenedithio)tetrathiafulvalene (BEDT‐TTF = ET) and paramagnetic Mn‐containing metallic complexes: κ′‐ET4[KMnIII(C2O4)3]∙PhCN (1) and ET[MnIICl4]∙H2O (2). Compound 1 represents the first Mn‐containing ET salt of the large Day’s series of oxalato‐based molecular conductors and superconductors formulated as (ET)4[AM(C2O4)3]∙G (A+ = H3O+, NH4+, K+, ...; MIII = Fe, Cr, Al, Co, ...; G = PhCN, PhNO2, PhF, PhCl, PhBr, ...). It crystallizes in the orthorhombic pseudo‐κ phase where dimers of ET molecules are surrounded by six isolated ET molecules in the cationic layers. The anionic layers contain the well‐known hexagonal honey‐comb lattice with Mn(III) and H3O+ ions connected by C2O42- anions. Compound 2 is one of the very few examples of ET salts containing ET2+. It also presents alternating cationic‐anionic layers although the ET molecules lie parallel to the layers instead of the typical almost perpendicular orientation. Both salts are semiconductors with room temperature conductivities of ca. 2 x 10-5 and 8 x 10−5 S/cm and activation energies of 180 and 210 meV, respectively. The magnetic properties are dominated by the paramagnetic contributions of the high spin Mn(III) (S = 2) and Mn(II) (S = 5/2) ions.

BEDT-TTF Salts Formed with Tetrahedrally Coordinated Zinc(II) Complex Anions

Twelve kinds of bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF or ET) cation radical salts with tetrahedrally coordinated zinc(II) complex anions were obtained by electrocrystallization; most of them were produced via the additional reaction of Lewis-basic cyano-containing anions [N(CN)2–, C(CN)3–, and Au(CN)2–] with ZnX2 (X = Cl–, Br–, and SCN–) that occurred during electrocrystallization. On the basis of the charge and arrangement of ET molecules, these salts were predominantly categorized into four groups: (A) isolated ET•+ dimers or tetramers, (B) infinite ET•+ ribbon, (C) infinite layers either with a peculiar ET0.5+ arrangement of ET molecules with partial charges other than +0.5, and (D) infinite layers of ET0.5+ molecules. In A, zinc(II) complex anions including a unidentate-coordinated C(CN)3 or Au(CN)2 group spatially interrupt the infinite arrangement of ET molecules. The ET•+ ribbon in B runs parallel to the pseudopolymeric chain of disordered Zn[C(CN)3]2Br22– ions. In C, two salts are semico...

Chemical Passivation of In0.53Ga0.47As(100) Using Ammonium Sulfide and Thiols

III-V compound semiconductors have superior electron and hole mobilities compared to silicon, which makes them alternative materials to fabricate transistors that are faster and use less energy. Since the oxides of III-V’s contain many defects and have undesirable electrical properties, aqueous passivation chemistries are needed to incorporate these materials into existing semiconductor processing lines. This study seeks to determine whether a thin (~2-3 nm) layer of sulfur or a sulfur-containing molecule can chemically passivate clean InGaAs surfaces to prevent oxide regrowth upon ambient exposure. The goal is to devise a liquid phase process to remove carbon contamination from the surface, etch the native oxides, and deposit a thin film to prevent the diffusion of molecular oxygen and water vapor to the clean surface of the semiconductor for at least one hour. In0.53Ga0.47As(100) on InP substrates (RMS=0.18 nm by atomic force microscopy) were cleaned in dilute SC1 solutions and etched for 1 min in 0.3 M HF or 1.0 M HCl followed by immersion in dilute solutions of 1-eicosanethiol (ET, 20 carbon atoms in chain) in ethanol or ammonium sulfide ((NH4)2S) in water. The chemical composition of the passivated surfaces was analyzed by x-ray photoelectron spectroscopy (XPS). The presence of InGaAs oxides was evaluated by comparing the In 3d, Ga 2p, As 2p and O 1s region of the XPS spectra of the substrates after different processes. The analysis of InGaAs etched for 1 min in HF or HCl showed that the surface reoxidized completely after only 4 min of ambient exposure (no surface roughening occured after etching). The main oxides present on the surface after the acid etching were the As3+ and Ga3+ states. When clean substrates were etched in HF or HCl and immersed for 20 min 4 mM ET and 0.02% (NH4)2S solutions, oxides were detectable on the surface after 4 min of atmospheric exposure, but the reoxidation of InGaAs was slowed down (after 60 min of ambient exposure, less oxides were present on the surface in comparison with the substrate that was not passivated, as shown in Figure 1). Additional tests showed similar results for 0.02% (NH4)2S passivation for 1 min and for 60 min, or for 20 min in 20% (NH4)2S, suggesting that the passivation is independent of (NH4)2S concentration or deposition time. From the XPS analysis, the passivation layer is bonding to the InGaAs surface in the form of sulfide (As1+ states observed in the passivated samples only). Only when InGaAs was passivated for 20 h in ET or for 20 min in (NH4)2S under a nitrogen atmosphere in a glove box, no detectable oxygen was observed in the O 1s region after exposing to air for a short time (4 min). Oxide regrowth was observed for longer ambient exposure times. To estimate the thickness of the passivation layer deposited, spectroscopic ellipsometry was used to measure the overlayer (ET, S and InGaAs oxides) on InGaAs after the passivation processes. An overlayer thickness of 0.8 nm was measured on InGaAs after passivating for 20 min in 0.02% (NH4)2S. The thickness of the overlayer on InGaAs after passivating for 20 h in 4 mM ET was 2.6 nm (the calculated molecular length of the ET molecule is 2.7 nm). These results show that the sulfur-based chemistries are bonding to the III-V’s but the resulting layer is not thick enough to prevent oxygen or water vapor from diffusing and reacting at the surface. We are working to understand how to densify the ET layer and control the thickness of layers deposited using (NH4)2S. Figure 1. XPS spectra of In0.53Ga0.47As(100) etched in 0.3 M HF and passivated for 20 min in 0.02% (NH4)2S in a nitrogen atmosphere (glove box). A control experiment where a water rinse was done instead of the passivation, exposed for 4 min to atmosphere, is shown in a). The passivated surface was exposed to atmosphere for b) 4 min, c) 8 min, d) 20 min and e) 60 min Figure 1

Metallic Charge‐Transfer Salts of Bis(ethylenedithio)tetrathiafulvalene with Paramagnetic Tetrachloro(oxalato)rhenate(IV) and Tris(chloranilato)ferrate(III) Anions

AbstractThe synthesis, crystal structure and physical characterization of three radical salts of the donor bis(ethylenedithio)tetrathiafulvalene (BEDT‐TTF or ET) and tetrachloro(oxalato)rhenate(IV) {[ReCl4(C2O4)]2–} or tris(chloranilato)ferrate(III) {[Fe(C6O4Cl2)3]3–} anions are reported. The isolated salts with ReIV are (ET)[ReCl4(C2O4)] [1, monoclinic, space group C2/c with a = 18.3409(3) Å, b = 10.8414(2) Å, c = 11.1285(3) Å, β = 99.9714(7)°, V = 2179.38(8) Å3, Z = 4] and (ET)4[ReCl4(C2O4)]·C6H5CN [2, monoclinic, space group P21/c with a = 11.8549(2) Å, b = 32.9079(5) Å, c = 36.4154(5) Å, β = 96.742(2)°, V = 14108.1(4) Å3, Z = 8]. The salt with FeIII is (ET)6[Fe(C6O4Cl2)3]·(H2O)1.5·(CH2Cl2)0.5 [3, triclinic, space group P$\bar {1}$ with a = 20.9489(7) Å, b = 26.7244(8) Å, c = 33.9132(11) Å, α = 68.262(3)°, β = 80.632(3)°, γ = 71.172(3)°, V = 16672.2(9) Å3, Z = 6]. Compounds 2 and 3 are two rare examples of paramagnetic molecular metals and the first ones in their respective families. Compound 3 has a very unusual θ21 phase and the largest number of independent ET molecules reported to date (18).

Evaluating model parameters of theκ- andβ′-type Mott insulating organic solids

We elucidate the model parameters for a series of organic crystals called $\ensuremath{\kappa}$- and ${\ensuremath{\beta}}^{\ensuremath{'}}$-type salts by constructing the maximally localized Wannier orbitals which reproduce the bulk energy band of the first-principles methods based on the density functional theory (DFT). These materials host a dimer Mott insulator, localizing one hole per dimerized ET molecules due to strong on-dimer interaction, ${U}_{\mathrm{d}}$. For all these materials, we evaluate the parameters of the two representative effective lattice models in units of molecule and on dimer, and clarify two issues. First, the conventional relationships between the two models called ``dimer approximation'' does not hold. Second, contrary to the previous semiempirical estimates, the degree of dimerization (which approximates ${U}_{\mathrm{d}}$) does not depend much on materials, and that the overall ground state properties are controlled by the degree of anisotropy of the triangular lattice, denoted as $|{t}_{c}/{t}_{a}|$ in units of dimers. We update the DFT estimates $|{t}_{c}/{t}_{a}|$ of $\ensuremath{\kappa}$-ET${}_{2}$Cu${}_{2}$(CN)${}_{3}$, showing that it falls on a class of regular triangle with the strongest degree of frustration.

Isolation and Crystallographic Characterization of Sm@C2v(3)-C80 Through Cocrystal Formation with NiII(octaethylporphyrin) or Bis(ethylenedithio)tetrathiafulvalene

Sm@C(2v)(3)-C(80) has been separated from the carbon soot produced by electrical arc vaporization of graphite rods doped with Sm(2)O(3) and purified. Its structure has been determined by single crystal X-ray diffraction using cocrystals obtained from either Ni(II)(octaethylporphyrin) (Ni(II)(OEP)) to form Sm@C(2v)(3)-C(80)·Ni(II)(OEP)·1.68(toluene)·0.32(benzene) or bis(ethylenedithio)-tetrathiafulvalene (ET) to produce Sm@C(2v)(3)-C(80)·ET·0.5(toluene). Thus, this study offers the first opportunity to compare a common endohedral fullerene in two different cocrystals. Both cocrystals provide consistent information on the basic structure of Sm@C(2v)(3)-C(80) but show that the distribution of samarium ion sites inside the carbon cage depends upon whether Ni(II)(OEP) or ET is present. The samarium ion is disordered in both structures, but the prominent sites lie slightly off the 2-fold symmetry axis of the cage. Computational studies at the B3LYP level indicate that Sm@C(2v)(3)-C(80) is more stable than any of the other six isomers of Sm@C(80) that obey the isolated pentagon rule (IPR). The surface electrostatic potential of the interacting components in the cocrystals has been examined to identify factors responsible for the ordering of the fullerene cages. The regions of the Ni(II)(OEP) or ET molecules that are closest to the fullerene display negative potential, while the corresponding regions of the endohedral fullerene show positive potential in a consistent fashion in both cocrystals.

Carrier doping to the organic Mott insulator by conjugating with tetrathiafulvalene

The electrical conductivity of the organic Mott insulator ET-F2TCNQ (ET = bis(ethylenedithio)tetrathiafulvalene, F2TCNQ = 2,5-difluoro-7,7,8,8-tetracyanoquinodimethane) crystal was found to be enhanced by conjugation with a tetrathiafulvalene (TTF) single crystal on its surface; surface sheet resistance decreased from 5 × l05 to 2 × 103 Ω/sq. The mechanism of this decrement was investigated through optical and atomic force microscopy measurements at the interface. When TTF was conjugated to the ET-F2TCNQ crystal, electron injection from TTF and complex formation between TTF and F2TCNQ occurred. Neutral ET molecules were consequently generated at the interface, and this charge doping broke the Mott insulating state.

Beyond the quantum spin liquid concept in frustrated two dimensional organic superconductors

AbstractThe occurrence of antiferromagnetism (AFM) in κ‐(ET)2X can be understood within an effective 1/2‐filled band with dimers of ET molecules containing one hole each. We argue that while this effective model can describe the presence of AFM, a complete description for these materials requires the correct carrier density of one‐half per molecule. For dimerized and strongly frustrated 1/4‐filled lattices we show that a singlet‐paired statecoexisting with charge ordering occurs that we have termed the paired electron crystal (PEC). Here we investigate the 1/4‐filled model on a dimerized lattice, showing regions where AFM, PEC, and the Wigner‐crystal occur. We point out the need to go beyond quantum spin liquid concepts for highly frustrated materials such as κ‐(ET)2Cu2(CN)3 and β′‐EtMe3Sb[Pd(dmit)2]2 which we believe are PECs at low temperatures.

1/f noise in the quasi-two-dimensional organic superconductor β′′-(ET)2SF5CH2CF2SO3

We performed resistance noise spectroscopy measurements of a bulk single crystal the quasi-two-dimensional organic superconductor β′′-(ET)2SF5CH2CF2SO3 and found generic 1/fα-type spectra. The temperature dependence of the nearly 1/f spectra are well described by a generalized random fluctuation model. Our data suggest that the number of fluctuators and/or their coupling to the electrical resistance depends on the temperature. The phenomenological model for the electronic fluctuations explains a pronounced peak structure in the low-frequency noise at around 100 K in terms of the thermally-activated conformational degrees of freedom of the ET molecules' ethylene endgroups.

Multifrequency ESR inET2MnCu[N(CN)2]4: A radical cation salt with quasi-two-dimensional magnetic layers in a three-dimensional polymeric structure

The radical cation salt, ${\text{ET}}_{2}\text{MnCu}{[\text{N}{(\text{CN})}_{2}]}_{4}$, $[\text{ET}=\text{bis}(\text{ethylenedithio})\text{tetrathiafulvalene}]$ with an unusual three-dimensional anionic polymeric network is studied by x-ray diffraction, static susceptibility measurements, and electron spin resonance (ESR) at frequencies between 9 and 420 GHz. The magnetic properties are determined by the alternating two-dimensional layers of the ${\text{Mn}}^{2+}$ ions of the network and the partially charged ET molecules. At ambient temperature the overlap between ${\text{Mn}}^{2+}$ ions and ET molecules is weak and an exchange integral $|{J}_{\text{Mn}\ensuremath{-}\text{ET}}|\ensuremath{\approx}4\ensuremath{\cdot}{10}^{\ensuremath{-}2}\text{ }\text{K}$ is estimated from their resolved ESR lines. At lower temperatures, ${\text{ET}}_{2}\text{MnCu}{[\text{N}{(\text{CN})}_{2}]}_{4}$ is not a simple system of weakly interacting paramagnetic ions in spite of the isotropic, Curie-like static susceptibility. There are first-order phase transitions at 292 K and in the range of 120--180 K. One of the lattice constants shows anomalous temperature dependence below 292 K. Anisotropic ESR shifts appear below 150 K, which we explain by demagnetizing fields of the platelike crystals and an exchange-narrowed fine structure. The latter contributes significantly to the shift when the populations of Zeeman levels are altered in high magnetic fields at low temperatures. We estimated the exchange coupling between ${\text{Mn}}^{2+}$ ions within a layer, ${J}_{\text{Mn-Mn}}\ensuremath{\approx}\ensuremath{-}48\text{ }\text{K}$ and determined the fine structure parameters below 150 K, showing a distortion in the plane of the ${\text{Mn}}^{2+}$ ions.

The first polymorph, κ″-(ET) 2Cu[N(CN) 2]Cl, in the family of κ-(ET) 2Cu[N(CN) 2] X ( X=Cl, Br, I) radical cation salts

The first polymorph, κ″-(ET) 2Cu[N(CN) 2]Cl, of the well known Mott insulator κ-(ET) 2Cu[N(CN) 2]Cl has been prepared and its crystal and electronic structures have been examined. The polymorph has monoclinic symmetry in contrast with the orthorhombic one of the isostructural κ-salts of the family (ET) 2Cu[N(CN) 2] X ( X=Cl, Br, I). The monoclinic phase exhibits a layered structure in which the conducting layers are packed in a κ-type arrangement and the anion sheets consist of polymeric zigzag chains formed by Cu[N(CN) 2]Cl units. The main structural differences with the orthorhombic κ-salts are that the anion sheets are disordered and the ET molecules are less planar. The new polymorph shows metallic type resistivity down to 4.2 K.

Impurity Effect on Superconducting Properties in Molecular Substituted Organic Superconductor κ-(ET)2Cu(NCS)2

We report an impurity effect in the organic superconductor κ-(ET) 2 Cu(NCS) 2 by substitution of the ET molecule with an analogue, bis(methylenedithio)tetrathiafulvalene (MT). The superconducting transition temperature decreases with increasing substitution. The in-plane magnetic penetration depth is enhanced with substitution, which is quantitatively attributed to the decrease in the in-plane mean free path. The enhancement of the penetration depth can also explain the reduction of the effective pinning in terms of the condensation energy.

Phase Transition from Mott Insulating Phase into the Charge Ordering Phase with Molecular Deformation in Charge-Transfer Salts κ-(ET)4[M(CN)6][N(C2H5)4]·2H2O (M = CoIII and FeIII)

Two isostructural charge-transfer salts κ-(ET)4[M(CN)6][N(C2H5)4]·2H2O (ET = bis(ethylenedithio)tetrathiafulvalene and M = CoIII, FeIII) were synthesized, and their crystal structures, Raman spectra, electrical conductivities, electron spin resonance (ESR), and static magnetic susceptibilities as a function of temperature were studied. At room temperature the salts contain two crystallographically independent ET molecules with an average charge of +0.5. Temperature dependence of the Raman spectra revealed that a charge disproportionation gradually occurs upon cooling, because new peaks originated from the ET+ and ET0 grow gradually. ESR, static magnetic susceptibility, and conductivity data, supported by band structure calculation, give us firm evidence of the phase transition from the Mott insulating phase with the fluctuation of charge order into the long-range charge ordered phase at around 150 K. The charge ordered ground state consists of (ET+)2 dimers and (ET0)2 dimers, where the neutral molecules a...

Molecular magnetic semiconductors formed by cationic and anionic networks: (ET)2Mn[N(CN)2]3 and (ET)2CuMn[N(CN)2

Crystals of (ET)2Mn[N(CN)2]3 (1) and (ET)2CuMn[N(CN)2]4 (2) with mono- and first bimetal dicyanamide anions were obtained and their structure, conducting and magnetic properties were investigated. The structure of 2 is not typical for ET radical cation salts and is characterized by the presence of a 3D polymeric anion built into the ET radical cation layers. The crystals of 1 exhibit a semiconducting behavior of conductivity and 2 undergoes a semiconductor I–semiconductor II phase transition at 295–291 K, which is specified by a jump of resistivity and the appearance of a hysteresis in the R(T) curves. The phase transition is accompanied by changes in the charge state of the ET molecules and intermolecular interactions in the crystal. Antiferromagnetic correlations of spins associated with anionic subsystems were found in both salts at temperatures lower than 25 K. Antiferromagnetic ordering in 1 has a long-range character. The effect of the spin frustrated state of localized spins on conducting electrons of ET subsystem was found in 1.

Unusual packing of ET molecules caused by π–π stacking interactions with TRISPHAT molecules in two [ET][TRISPHAT] salts (ET = bis(ethylenedithio)tetrathiafulvalene, TRISPHAT = (tris(tetrachlorobenzenediolato)phosphate(V)))

The synthesis, structure and physical properties of two new radical salts formed with the organic donor bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF or ET) and a racemic mixture of the chiral anion (tris(tetrachlorobenzenediolato)phosphate(V)) (TRISPHAT) are reported. The structure of the salts (ET) 4[TRISPHAT] 4 · 3.5H 2O ( 1) and (ET)(TRISPHAT) · CH 2Cl 2 · CH 3CN ( 2) has been solved by X-ray single crystal diffraction. Unusual packings of ET molecules are obtained in the two structures. The electrical properties indicate that both compounds are insulators. This is in agreement with the isolation of the ET molecules and their complete ionization. On the other hand, the anisotropy of the ESR lines has been studied by Q-band ESR spectra.

Examination of the Charge-Sensitive Vibrational Modes in Bis(ethylenedithio)tetrathiafulvalene

We reinvestigated the two C=C stretching modes of the five-membered rings of ET (ET = bis(ethylenedithio)tetrathiafulvalene), namely, nu(2) (in-phase mode) and nu(27) (out-of-phase mode). The frequency of the nu(27) mode of ET(+) was corrected to be approximately 1400 cm(-1), which was identified from the polarized infrared reflectance spectra of (ET)(ClO(4)), (ET)(AuBr(2)Cl(2)), and the deuterium- or (13)C-substituted compounds of (ET)(AuBr(2)Cl(2)). It was clarified from DFT calculations that the frequency of the nu(27) mode of the flat ET(0) molecule was significantly different from that of the boat-shaped ET(0) molecule. We obtained the linear relationship between the frequency and the charge on the molecule, rho, for the flat ET molecule, which was shown to be nu(27)(rho) = 1398 + 140(1 - rho) cm(-1). The frequency shift due to oxidation is remarkably larger than that reported in previous studies. The fractional charges of several ET salts in a charge-ordered state can be successfully estimated by applying this relationship. Therefore, the nu(27) mode is an efficient probe to detect rho in the charge-transfer salts of ET. Similarly, a linear relationship for the nu(2) mode was obtained as nu(2)(rho) = 1447 + 120(1 - rho). This relationship was successfully applied to the charge-poor molecule of theta-type ET salts in the charge-ordered state but could not be applied to the charge-rich molecule. This discrepancy was semiquantitatively explained by the hybridization between the nu(2) and nu(3) modes.

The determination of the effective dielectric constant of micelles and microemulsions

Pyridinium N-phenoxide betaine, commonly known as ET(30) molecule, is used to probe the polarity of the cetyltrimethylammonium bromide (CTAB) micelle and the didodecyldimethylammonium bromide (DDAB) bicontinuous microemulsion systems. The observed ET(30) values of these aggregated systems were observed to lie within those of the C1 through C5 alcohols, and have good correlation with their respective dielectric constants, ε. The effective dielectric constant of the micelles and microemulsions were determined using the correlation obtained from the alcohols’ ET(30) values correlated with their corresponding dielectric constants. Generalized equations, usable for all micelles, irrespective of the type of surfactant was developed and the effective dielectric constant values obtained using the equation were in good agreement with the literature values. An equally satisfactory equation based on the ratio of surfactant and oil (S/O) for the bicontinuous microemulsion system was also developed.