Organic Radical Cations Research Articles

Electron transfer photochemistry of bifunctional strained-ring and unsaturated systems

Abstract

Generation, entrapment and reactivity of long-lived organic carbocations and radical cations within a supramolecular assembly: Ca Y zeolite

Diarylethenes spontaneously form the corresponding radical cations and carbocations upon inclusion within activated Ca Y zeolite; oxygen plays an important role in the generation of the radical cations.

A Molecular Antiferromagnet TMTSF·FeCl4

Abstract A semiconducting organic radical cation salt with a magnetic anion, TMTSF·FeCl4 (ρrt = 40 Ωcm), was prepared. The crystal undergoes an antiferromagnetic ordering below TN = 4 K with the easy axis perpendicular to the TMTSF stacking direction. X-ray crystallographic analysis reveals that Cl atoms of the anions closely contact with Se atoms of the donor molecules and suggests that the spin ordering is mediated by magnetic interaction between donors and anions.

Syntheses, Characterization and X-Ray Crystal Structures of Tetrakis(Ethylthio)Tetrathiafulvalenium Hexachlorodicopper(II) and Hexabromodicopper(II)

Abstract Oxidation of tetrakis(ethylthio)tetrathiafulvalene (TTC2-TTF) with CuCl2 and CuBr2 in acetonitrile yielded the organic radical cation salts, (TTC2-TTF)2[Cu2Cl6] 1 and (TTC2-TTF)2[Cu2Br6] 2, whose structures have been determined by X-ray structure analysis. Both 1 and 2 crystallize in the triclinic system, space group P 1, with one molecule per unit cell. 1: a = 12.065(4), b = 12.644(3), c = 8.988(2) A, α = 103.54(2), β = 90.24(2), γ = 112.42(2)°. 2: a = 12.330(3), b = 12.647(2), c = 8.956(2) A, α = 101.72(2), β = 94.66(2), γ = 111.69(1)°. Both structures consist of two segregated stacks of TTC2-TTF+ donors and Cu2X6 2- acceptors associated via short S···X contacts. Consistent with the structural results, the two compounds exhibit low electrical conductivities with [sgrave]25°C being 4 × 10−8 and 8 × 10−8 S cm−1 for 1 and 2, respectively.

Molecular Compounds Exhibiting Coupled Conducting and Magnetic Properties and Based on (cation)n[M(dmit)]2 and (BETS)2(anion) Salts

Abstract A systematic study has been carried out on a range of metal complexes of the type (cation)n[M(dmit)2] (cation = NHyR4-y; y = 1 or 2; n = x, 1, 2; R = ethyl, propyl or butyl, or cation = organic radical cations containing one or two TTF moieties; M = Ni or Pd and dmit = 2-thioxo-1,3-dithiole-4,5-dithiolato). The synthesis of these complexes, the crystal structure of (NHBu3)2[Ni(dmit)2] and neutral [Ni(dmit)2], their solution redox behaviour and the solid state conductivities of the non-integer oxidation state compounds obtained by electrocrystallization techniques are presented. Synthesis, structure and properties of new compounds of the family of (BETS)2(anion) compounds with (CuxCly)n- and [(FeCl4)1−x(GaCl4)x]− anions are described.

Nuclear magnetic relaxation of1H in organic cation radical saltm-MPYNN+X− (X=ClO4, BF4)

The nuclear spin-lattice relaxation timeT 1 of1H in the organic cation radical saltm-MPYNN+X− (X=ClO4, BF4) has been measured in the temperature range 1.5∼200K and in the field range 1∼70kOe. The experimental results in high fields were well interpreted in terms of flip-flop relaxation process involving the pairs of ferromagnetic dimers, whose energy scheme consists of lower triplet- and upper singlet-states with the gap energy of 20K. An appreciable increase of the relaxation rate in low fields below about 10kOe was explained by the direct relaxation process due to the band-like spread of each Zeeman level.

On the deprotonation of the cation radicals of substituted ethylenes. A heterolytic or homolytic process?

Abstract The deprotonation of several cation radicals of substituted ethylenes in a monohydrated, monoammoniated or dihydrated cluster has been theoretically studied using an ab initio method through the 6-31G(D, P) basis set. It has been found that the cation radicals are π radicals, whereas the corresponding deprotonated species are σ radicals, the deprotonation process involving an intramolecular electron transfer from a σ to a π molecular orbitals. The experimental findings about the deprotonation reactions of organic cation radicals that have charge delocalized from the departing proton have been confirmed. The dissociation of the carbon-hydrogen bond begins with the homolytic stretching of the CH bond and then becomes a heterolytic dissociation, the transition state appearing very near the region of the crossing between both diabatic potential energy surfaces. The global proton transfer can therefore be described as a concerted transfer of a hydrogen atom and an electron in opposite senses.

Deprotonation of organic radical cations. Chemical evidence for proton transfer between 9,10-dihydroanthracence radical cations and superoxide radical anions

Deprotonation of organic radical cations. Chemical evidence for proton transfer between 9,10-dihydroanthracence radical cations and superoxide radical anions

Deprotonation of organic radical cations. Chemical evidence for proton transfer between 9,10-dihydroanthracence radical cations and superoxide radical anions

Deprotonation of organic radical cations. Chemical evidence for proton transfer between 9,10-dihydroanthracence radical cations and superoxide radical anions

Thin films of the organic conductor (BEDO-TTF) 2.4I 3

We report results on the fabrication of thin films of the organic radical cation salt (BEDO-TTF) 2.4I 3. The title compound is an organic metal with a room temperature dc-conductivity of 180 – 360 S/cm. On amorphous substrates as quartz glass and silicon wafers ( Si SiO 2 ), we found one or more orientations of the crystalline material with respect to the substrate plane. On NaCl there is only a single, very strong Bragg reflection, which is due to the very good, substrate-induced orientation of the film. Scanning electron microscopy reveals growth of grains on the quartz glass substrates, whereas on NaCl large smooth areas with 1 to 10 μm edge size are observed. The dc-conductivity shows a slightly activated behaviour with an activation energy of 20 meV and a room temperature value of 1 S/cm.

Structure and Properties of an Organic Metal (BEDT-TTP)2I3

Abstract An organic radical-cation salt (BEDT-TTP)2I3, where BEDT-TTP (2,5-bis(4,5-ethylenedithio-1,3-dithiol-2-ylidene)-1,3,4,6-tetrathiapentalene) is a bis-fused analog of BEDT-TTF (bis(ethylenedithio)tetrathiafulvalene), has a donor arrangement similar to β-(BEDT-TTF)2I3. (BEDT-TTP)2I3 shows high conductivity 900 S cm−1 at room temperature, and retains its metallic conductivity down to 0.5 K.

Dc-conduction mechanism and Peierls gap in organic and inorganic charge-density-wave conductors.

It has been shown in a recent analysis of the temperature dependence of the dc conductivity of the quasi-one-dimensional conductor (fluoranthene${)}_{2}$${\mathrm{PF}}_{6}$ that in spite of the occurrence of the Peierls transition to a charge-density-wave ground state (formally implicating polarons as excitations), the dc conduction is essentially due to electron-hole transport in bands and acoustical phonon scattering of the carriers. The theory allows for the determination of the temperature dependence of the Peierls gap below and the fluctuating pseudogap above the transition temperature. Our dc-conductivity measurements confirm that a common temperature dependence occurs in organic radical cation salts and in inorganic materials from the groups of the blue bronzes and the transition metal tetrachalcohalogenides. These materials are rather different especially with respect to the nature of the states forming the conduction band and the filling of the latter. Here we reduce the needed information on the band structure to a minimum connected with optical data and extend the theory to the case of a gap small compared to ${\mathit{k}}_{\mathit{B}}$T. The theory is applied to (Fa${)}_{2}$${\mathrm{PF}}_{6}$, ${\mathrm{K}}_{0.30}$${\mathrm{MoO}}_{3}$, and (${\mathrm{TaSe}}_{4}$${)}_{2}$I as representatives of the above-mentioned groups of materials. From the measured conductivity data the temperature dependence of the Peierls gap below and the pseudogap above the transition temperature are determined as well as several conductivity-related quantities. Similarities and differences of the investigated materials are discussed.

EPR studies of the 2-D magnetic system in an organic cation radical salt, m-MPYNN+·X−

EPR measurements were carried out on a single crystal of m-N-methylpyridinium nitronyl nitroxide perchlorate which consists of a 2-D bond-alternated hexagonal lattice. Angular dependence of the linewidth ΔH pp shows minimums at the magic angles, and can be well interpreted with the theoretical equation for the 2-D magnetic system, ΔH pp= A(3cos2 θ-1) 2+ B. Temperature dependence of ΔH pp shows an anomaly between 50 K and 100 K, which could be relevant to freezing of the orientational disorder of the perchlorate ion. Angular dependence of the g-value confirms the 2-D character of the magnetic system. Below 50 K, the EPR signal is affected by the demagnetizing effects.

Preparation and magnetic properties of saponite clays intercalated with stable organic radicals

The organic radical cations, 2-(3- and 4-N-methylpyridinium)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-1-oxyl 3-N-oxide, are intercalated into saponite clay {Na0.46[Si3.54Al0.46Mg3O10(OH)2]·nH2O} by means of cation exchange, and display Curie paramagnetic behaviour in the interlayers.

OVERVIEW OF ORGANIC SUPERCONDUCTORS

Organic materials which are usually used for insulators, were shown to be an electrical conductor by H. Akamatsu, H. Inokuchi, and Y. Matsunaga in 1954. Moreover, J.P. Ferraris et al. showed that TTF [center dot] TCNQ was stably metallic down to around 60 K in 1973. Because of a low dimensionality of organic compound, however, a stabilization of an electronic state and a destabilization of a periodic lattice constructed a charge density wave which led a metal-insulator transition (a Peierls transition). After overcoming this low dimensionality, D. Jerome et al. discovered the first organic superconductor, (TMTSF)[sub 2] PF[sub 6] ([Tc] = 0.9 K (12kbar)) in 1980. Then with the resisting up of [Tc] constantly, the superconductor [kappa]-(BEDT-TTF)[sub 2](NCS)[sub 2] ([Tc] = 10.4 K) was found in 1987 and the [Tc] of [kappa]-(BEDT-TTF)[sub 2]Cu[N(CN)[sub 2]]Cl, 12.8 K at 0.3kbar, is the highest among the TTF family. Moreover, when the authors included the C[sub 60] system is included as molecular superconductor, the [Tc] = 33 K of Cs[sub 2]RbC[sub 60] reaches the starting point of oxide superconductors. In this paper, the history of organic conductors is described in Sec. 2. In Sec. 3, the author chooses the typical example of organic superconductor,more » [kappa]-(BEDT-TTF)[sub 2]Cu(NCS)[sub 2], and the preparation, crystal structure, chemical and physical properties are reviewed. In Sec. 4, the mechanism of organic superconductors is discussed and the future of organic superconductors is finally presented. 118 refs.« less

ESR studies of organic radical cations in zeolites

ESR studies of organic radical cations in zeolites

Evaluation of AM1‐calculated radical cation ion‐neutral complexes

AbstractAM1 semiempirical molecular orbital calculations are reported for 20 ion‐neutral complexes, including hydrogen‐bonded complexes, presumably involved in the gas‐phase unimolecular decomposition of simple organic radical cations. The systems investigated are [C2H4O2]˙+, [C2H5NO]˙+, [C2H6O]˙+, [C2H6O2]˙+, [C3H6O]˙+, [C3H6O2]˙+, [C3H8O]˙+, and [C3H8O2]˙+. The AM1 results are compared with ab initio molecular orbital calculations at different levels of theory up to MP3/6‐31G(d, p)//SCF/6‐31G(d) + ZPVE and the available experimental data. AM1 fails to predict some local minima and the equilibrium geometries calculated for several complexes are found to be qualitatively different from those predicted by the ab initio calculations. However, reasonable agreement is generally found for the stabilization energies of the complexes toward dissociation into their loosely bound components. © John Wiley & Sons, Inc.

Organic radical cations abstract methylene from ketene to produce stable distonic ions

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTOrganic radical cations abstract methylene from ketene to produce stable distonic ionsRebecca L. Smith, Rebecca L. Franklin, Krista M. Stirk, and Hilkka I. KenttamaaCite this: J. Am. Chem. Soc. 1993, 115, 22, 10348–10355Publication Date (Print):November 1, 1993Publication History Published online1 May 2002Published inissue 1 November 1993https://doi.org/10.1021/ja00075a059RIGHTS & PERMISSIONSArticle Views122Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (799 KB) Get e-Alerts Get e-Alerts

Hydrogen-bond tuning of macroscopic transport properties from the neutral molecular component site along the sries of metallic organic-inorganic solvates (BEDT-TTF)4Re6Se5Cl9.[guest], [guest = DMF, THF, dioxane

A series of single crystals of tetrakis[3,4,3',4'-bis(ethylenedithio)-2,2',5,5'-tetrathiafulvalene] Re 6 Se 5 Cl 9 .-guest] (2a-d) have been prepared where the monoanion is a hexanuclear chalcohalide rhenium cluster and the neutral guest molecules are dimethylformamide (DMF) in 2a (monoclinic modification) and 2b (triclinic modification), tetrahydrofuran (THF) in 2c, and dioxane in 2d. All four compounds present the same basic structural organization in which conducting organic cation radical slabs are sandwichdn by inorganic cluster monoanion layers

Charge transport in the quasi-one-dimensional organic charge density wave conductor (fluoranthene) 2X

Due to its simple crystal structure the organic radical cation salt (fluoranthene) 2X can serve as a model system for quasi-one-dimensional conductors. The temperature dependence of the dc conductivity exhibits the typical behaviour of a quasi-one-dimensional metal with a Peierls transition at about 180 K to a charge density wave (CDW) ground state. Above the Peierls transition σ |;( T) can be described quantitavely within a model of CDW fluctuations leading to a pseudo gap in the electronic density of states. Below, the existence of a real energy gap 2 Δ( T) with a modified BCS-like temperature dependence determines the charge transport. On crystals from different charges intrinsic energy gaps 2 Δ(0) = 120–180 meV have been found due to deviations from the ideal 2:1-stoichiometry in (FA) 2X. For electrical fields exceeding a small sample dependent threshold ( E T = 0.1–1 V/cm) nonlinear conductivity and other collective CDW transport phenomena can be observed. On crystals with different energy gaps 2Δ(0) we observe significant differences in dynamics of the nonlinearity as well as in the magnitude of the threshold field. Our observations indicate that defect and commensurability pinning of the CDW are of great importance for the nonlinear transport properties of (FA) 2X. On thermally quenched samples the existence of metastable states has been found, due to pinning of the CDW by randomly positioned impurities.