Octahedral Anions Research Articles

Synthesis and structure of the rhodium complex [Ph3MeP][RhBr4(DMSO)2-trans

The ionic complex, methyltriphenylphosphonium(I) trans-bis(dimethylsulfoxido)tetrabromorhodiate, was prepared by the reaction of sodium hexabromorhodiate with methyltriphenylphosphonium bromide in dimethyl sulfoxide and studied by X-ray diffraction. The phosphorus atom in the [Ph3MeP]+ cation has an almost undistorted tetragonal coordination (the CPC angles are 108.3(2)°–110.5(2)°, the P-C bonds are 1.779(6)–1.798(4) A). In the octahedral complex anion [RhBr4(DMSO)2-trans]−, the dimethyl sulfoxide ligands are coordinated by the sulfur atoms (Rh-S, 2.344(1), 2.336(1); Rh-Br, 2.4839(7)–2.4934(7) A; SRhS, 179.56(7)°; trans-BrRhBr, 179.30(3)°, 179.56(7)°) (CIF file CCDC no. 978748).

Hydrogen-Bonded Supramolecular Architectures Based on Tris(Hydranilato)Metallate(III) (M = Fe, Cr) Metallotectons

Here we report on the synthesis and characterization of two isostructural mononuclear complexes of formula [(Ph)4P]3[M(H2An)3]·6H2O (M = Fe(III) (1) or Cr(III) (2); H2An = H2C6O42– = dianion of 3,6-dihydroxy-1,4-benzoquinone (DHBQ)) as suitable metallotectons for the preparation of H-bonded supramolecular architectures. The crystal structure of 1 consists of homoleptic tris-chelated octahedral complex anions [Fe(H2An)3]3– surrounded by crystallization water molecules and (Ph)4P+ cations. The metal complexes are involved in an extensive network of moderately strong hydrogen bonds (HBs) between the peripheral oxygen atoms of the ligand and crystallization water molecules. These interactions are responsible for the formation of supramolecular layers that run parallel to the a crystallographic axis, showing an unprecedented H-bonded 2D architecture in the family of the anilato-based H-bonded networks. The supramolecular interactions present in the structure were investigated analyzing the properties of the Hirshfeld surface (HS), which points out the crucial role of the HBs in the construction of the overall supramolecular architecture, whereas the electronic properties of the metal complex were studied by means of DFT calculations. The magnetic susceptibility measurements reveal the expected paramagnetism of the two compounds with quasi-isolated spin centers.

Hexafluorosilicates with antibacterial active guanidine containing cations

The present research has studied the spectral data, thermochemical transformations and hydrolysis of hexafluorosilicates with guanidine containing cations (C22H32Cl2N10)SіF6 (І) and (C21H45N9)(SiF6)1.5 (ІІ) for their potential use as caries-preventive and antibacterial agents. Hexafluorosilicates of the com position I and II were separated as crystalline products of interaction of hexafluorosilicic acid with the methanol solutions of chlorhexidine hydrochloride and polyhexamethylene guanidine hydrochloride. The compounds isolated have been characterized by IR, NMR 19 F, mass-spectrometry, thermogravimetric analysis, potentiometry. According to IR spectroscopy data, “onium” hexafluorosilicates I and II have ionic structures. The vibrations of the groups ν(NH), ν(N + H2) in salts I and II appear as strong absorption bands at 3360-3180 cm –1 ; δ(N + H2) vibrations appear at 1634 and 1637 cm –1 . The strong ν(SiF) and δ(SiF2) stretches of SiF6 2– anions are observed in their characteristic regions (at 744, 734 and 482 cm –1 , respectively). The singlet character of ν(SiF) and δ(SiF2) vibrations indicates the absence of noticeable distortion of symmetry of SiF6 2– anion with regard to Oh. The NMR 19 F spectra of compounds I and II (in DMSO-d6 solutions) have one resonance at –136,70, –135,09 ppm (SiF6 2– ); additional resonance at –123,14 ppm, in the case of II it can be related to the octahedral complex anion [SіF5(ДМСО)] – . The results of thermogravimetric analysis are consistent with a multi-stage thermolysis scheme for hexafluorosilicates I and II. The temperatures of thermolysis beginning of complexes I and II are 270 and 100°C, respectively. The compounds I and II studied are characterized by the predicted tendency to hydrolysis in dilute aqueous solutions with formation of orthosilicic acid and fluoride ions, and it allows considering these salts as potential anticaries agents. The study of the biological activity of these compounds is the subject of further investigations. In recent years, several research groups consisting of experts from Japan, the United States [10-13] and Armenia [1, 8] demonstrated the possible use of ammonium and amino acids hexafluorosilicates as caries-preventive and hyposensitive agents in dental practice. These results [1, 8, 10-13] allow to consider the “onium” hexafluoro silicates as a promising new class of drugs possessing a number of advantages compared to the conventional agents of fluoride caries therapy such as sodium and po tassium fluorides, silver diamine fluoride, tin fluoride and sodium monofluorophosphate. The active components of treatment and prevention of dental caries are also antibacterial agents, including high efficient guanidine de rivatives (chlorhexidine, polyhexamethylene guanidine hydrochloride, etc.) [9, 13]. In principle, introducing guanidine containing cations possessing the antibacterial action into the composition of hexafluorosilicate allows to obtain compounds for which the caries-preventive effect of the anion is intensified by the bactericidal action of the cation. The aim of this work is the synthesis, the study of the structure and properties of chlorhexidine (CH) and polyhexamethylene guanidine (PHMG) hexafluorosilicates – the first representatives of fluoride-containing salts com bined with cations exhibiting the antibacterial activity. Materials and Methods The synthesis of hexafluorosilicates was performed by the ion exchange reaction between methanol solu

Structural characterization and properties of bis (1,4-H2-1,2,4-triazolium) pentachlorobismuthate (III) and cocrystal of ammonium chloride with tris (1,4-H2-1,2,4-triazolium) hexachlorobismuthate (III)

The crystal structure of two novel 1,2,4-triazolium analogues: [C2N3H4]2[BiCl5] (TBC) and [NH4][C2N3H4]3[BiCl6][Cl] (TCBA), isolated from one system, has been determined. The structure of TCBA is built up from cationic substructures consisting of 1,2,4-triazolium and ammonium cations, [Cl]-, and discrete [BiCl6]3- octahedral anions. The two-component cationic sublayer of TCBA is unique in the case of halobismuthates(III). TCBA adopts the triclinic space group (P1¯) at 100K. Differential scanning calorimetry (DSC) and dilatometric measurements showed that it undergoes reversible first-order phase transition (PT) at 420/405K (heating/cooling) governed by an ’order–disorder’ mechanism. The crystal structure of TBC (Cmca at 100K) contains the [BiCl5]∞2- chains of cis-connected octahedra and a hydrogen-bonded array of 1,2,4-triazolium cations. The statistical disorder of the 1,2,4-triazolium cations is found at low temperatures. No PT is detected between 100 and 400K in TBC.

Binding and removal of octahedral, tetrahedral, square planar and linear anions in water by means of activated carbon functionalized with a pyrimidine-based anion receptor

Enhanced anion recovery from water is achieved upon functionalization of activated carbon with polyamine groups.

Dual modes of binding on the hexafluorosilicate anion by a C3vsymmetric flexible tripodal amide ligand in solid state

Apara-nitrophenyl functionalizedC3vsymmetric flexible tripodal amide ligand,L, shows remarkable solvent dependent dual binding behaviour towards the octahedral hexafluorosilicate anion in solid state.

Structural properties of the inner coordination sphere of indium chloride complexes in organic and aqueous solutions

The nature of the inner coordination sphere of In(3+) present in both the organic and aqueous solutions during the solvent extraction of In(3+) from an aqueous HCl solution with tri-n-octyl amine (TOA) was investigated by In K-edge XAFS. This information was then used to clarify the details of the extraction properties of indium chloride anion complexes with TOA. In aqueous HCl solution (0.1-10 M), In(3+) exists as octahedral anion complexes, [InCln(H2O)6-n](3-n) (n ≥ 4); the [InCl6](3-) complex is dominant at 10 M HCl. The extraction of In(3+) from HCl solution with TOA was performed using two kinds of diluents: nitrobenzene (NB) or n-dodecane (DD), which contained 20 vol% of 2-ethylhexanol as an additive. The stoichiometric composition of the extracted complexes, which is estimated from the distribution ratios of In(3+), is affected by the diluents and the HCl concentration of the aqueous phase; the apparent values of TOA/In(3+) in the extracted complex are 3 for DD-1 M HCl (diluent-aqueous phase) and DD-5 M HCl, 2 for NB-1 M HCl and NB-5 M HCl, and 1 for NB-10 M HCl. The EXAFS analysis of these extracted complexes shows that the In(3+) has ∼4 Cl(-) at ∼2.336 Å and no H2O in the inner coordination sphere; additionally, the shape of the XANES suggests that their coordination geometry is tetrahedral. Therefore, the same tetrahedral [InCl4](-) complex is formed during the extraction in spite of the variation in the stoichiometric composition (TOA/In(3+) = 1-3) of the extracted complexes.

Hexane-1,6-diammonium hexafluorosilicate

The asymmetric unit of the title organic–inorganic molecular salt, C6H18N2 2+·SiF6 2−, consists of one anion and one cation together with half of each of two cations and two anions located on inversion centres. The SiF6 2− octa­hedral anions are arranged to form sheets parallel to (011), which are linked into a three-dimensional network by the organic cations through N—H⋯F hydrogen bonds.

Ionic coordination complexes based on [Re6S8(CN)4L2]n– (L = OH–, NH3; n = 2, 3) cluster anions, and Ni(II) and Cd(II) ammine cations

Two new complexes containing M(II) ammine cations (M = Ni, Cd) and octahedral rhenium(III) thiocyanoammine and thiocyanohydroxoammine cluster anions, [Ni(NH3)6][Re6S8(CN)4(NH3)2]∙2H2O (1) and [Cd(NH3)6][{Cd(NH3)5}{Re6S8(CN)4(OH)(NH3)}]2∙5H2O (2), have been synthesized by hydrothermal reactions starting from Cs1.83K2.17[Re6S8(CN)4(OH)2]∙2H2O. The compounds were structurally characterized by single-crystal X-ray diffraction analysis, elemental analysis, energy dispersive spectroscopy, and IR spectroscopy. Both compounds adopt monoclinic crystal structures composed from discrete ionic species which are held together by multiple hydrogen bonds between CN–, OH–, and NH3 ligands and lattice water. 2 consists of {Cd(NH3)5}2+ attached to the OH group of the [Re6S8(CN)4(OH)(NH3)]3– cluster anion via the Re–OH–Cd linkage.

Mononuclear anionic octahedral cobalt(III) complexes based on N-salicylidene-o-aminophenol and its derivatives: Synthetic, structural and spectroscopic studies

The reactions of Co(II) sources with N-salicylidene-o-aminophenol (H2saph), N-salicylidene-o-amino-4-methylphenol (H2saph-4Me) and N-salicylidene-o-amino-4-chlorophenol (H2saph-4Cl) were studied in MeOH. The new solid complexes (Bu4nN)[CoIII(saph)2] (1), (Et3NH)[CoIII(saph-4Me)2]⋅MeOH⋅MeCO2H (2⋅MeOH⋅MeCO2H) and (Et3NH)[CoIII(saph-4Cl)2]⋅MeOH⋅MeCO2H (3⋅MeOH⋅MeCO2H) have been isolated and their structures determined by single-crystal, X-ray crystallography. The three compounds contain the mononuclear, low- spin octahedral anion [CoIIIL2]- (H2L=H2saph, H2saph-4Me, H2saph-4Cl), in which both L2− ligands act as tridentate chelating, meridional ONO donors. The crystal structures of 2⋅MeOH⋅MeCO2H and 3⋅MeOH⋅MeCO2H are built through H-bonding and π–π stacking interactions. The new complexes were characterized by elemental analyses and spectroscopic (IR, Raman, UV/VIS, 1H NMR) data. All data are discussed in terms of the nature of bonding and known structures.

Structure and thermoelectric properties of EuTi(O,N)3 ± δ

After partial substitution of nitrogen for oxygen in EuTiO3, the crystal structure, thermoelectric properties, morphology, and electronic structure of the products were analyzed and compared with pristine EuTiO3. The space group of EuTi(O,N)3 ± δ was orthorhombic Pnma due to the tilt and rotation of the anion octahedra, compared to cubic Pm3¯m of EuTiO3 (at room temperature). The thermoelectric properties of oxynitride polycrystalline bodies sintered in three different ways were investigated in the temperature range of 300 K < T < 950 K. The Seebeck coefficients (S) of the oxynitrides were lower compared with the oxide, and the electrical resistivities (ρ) were increased about one order of magnitude. The activation energies (EA) indicated a larger band gap of EuTi(O,N)3 ± δ when compared to the pristine EuTiO3 (∼1.3 eV compared to 0.98 eV). A morphological characterization by transmission electron microscopy and scanning electron microscopy illustrated intrinsic nanopores within the individual particles and weak grain-interconnections indicating poor intergrain electron transport. Ab initio calculations of the electronic structures confirmed a larger band gap of the distorted crystal structure of the oxynitride and showed a decrease of the density of states at the Fermi level, explaining the reduction of the measured S.

First-Principles Study of Structural Prototypes for NaAlH4: Elevated Pressure Polymorph in Symmetry Fmm2 Leads to a Single-Step Decomposition Pathway

In situ high-temperature X-ray diffraction and high-temperature and pressure nuclear magnetic resonance studies of the complex metal hydride NaAlH4 have strongly suggested an intermediate phase or phases. In order to search for these phases, structural prototypes of NaAlH4 were generated using the method of prototype electrostatic ground states (PEGS). Structural motifs included tetrahedral [AlH4]− and [AlH6]3– octahedral anions. Structures were produced with Al–H coordination numbers from 4 to 6 and were examined for thermodynamic stability. We present a high-temperature phase in symmetry Fmm2 that is lower in total free energy than all currently known structures, including a structure presented in space group Cmcm, due to low rotational barriers for [AlH4]− anions. The Na–Al–H phase diagram, calculated in the harmonic approximation, indicates that at higher pressures, the I41/a NaAlH4 phase transforms to Fmm2 symmetry, which then decomposes directly into NaH and Al, eliminating the Na3AlH6 intermediate. The transition to Fmm2 is predicted to occur near 320 K at calculated pressures of about 1–2 bar. We also present calculations of NMR 27Al and 23Na chemical shifts for the structural prototypes. These results indicate a monotonic decrease of the 27Al chemical shift with increasing Al–H coordination number with an unambiguous identification of an Al/H ratio of 1:4 for the unknown high-temperature phase S105 identified by Conradi and co-workers (Conradi, M. S. et al. J. Phys. Chem. Lett. 2010, 1, (15), 2412−2416).

Anion−π Interactions in Supramolecular Architectures

The study of the noncovalent force between π-acidic aromatic systems and anions, referred to as the anion-π interaction, has recently emerged as a new branch of supramolecular chemistry. The anion-π contact is complementary to the cation-π interaction, a prominent noncovalent force involved in protein structure and enzyme function. Until recently, the scientific community had overlooked the anion-π interaction due to its ostensibly counterintuitive nature. Pioneering theoretical studies in 2002, however, established that anion-π interactions are energetically favorable (~20-70 kJ/mol) and prompted a flurry of reports in support of their existence. The interest in anion-π contacts was further fueled by the importance of anions in key chemical and biological processes and the involvement of π-rings in anion recognition and transport. Anion-π interactions hold great promise for the design of selective anion receptors, hosts or scaffolds, colorimetric sensors, and catalysts and may also affect biological functions. Currently, the area of anion-π research is highly topical in the scientific community and on a meteoric rise in the chemical literature. This Account highlights our leading findings in this burgeoning area. Our work has focused on comprehensive investigations of several unprecedented supramolecular systems, in which the anions and their close anion-π contacts are the driving elements of the final architectures. We surveyed several heterocyclic π-acidic aromatic systems amenable to anion-π contacts and explored the subtle interplay between ligand π-acidity, anion identity, and metal ions in mediating the ensuing self-assembled architectures. The reactions we performed between solvated first-row transition metal ions and the π-acidic ligands bptz (3,6-bis(2-pyridyl)-1,2,4,5-tetrazine) or bmtz (3,6-bis(2-pyrimidyl)-1,2,4,5-tetrazine) resulted in unprecedented metallacycles. Our investigations revealed that the identity of the encapsulated ion dictates the metallacycle nuclearity and close anion-π contacts are critical for the metallacycle stability. Our X-ray crystallographic, NMR spectroscopic, and mass spectrometric (MS) studies demonstrated that the tetrahedral ([BF4](-), [ClO4](-)) and octahedral ([SbF6](-), [AsF6](-), [PF6](-)) anions template discrete molecular squares and pentagons, respectively. The metal ions occupy the vertices, and bptz or bmtz moieties span the edges of the metallacycles. The encapsulated anions occupy the π-acidic cavities of the metallacycles and establish multiple close directional F/O···C(tetrazine) contacts with the edges. The observation of notable (19)F solid-state NMR chemical shifts reflects the short contacts of the encapsulated anions, findings that we corroborated by DFT calculations. The solution NMR data support the conclusion that bona fide metallacycle templation and interconversion between the metallacycles in solution occurs only in the presence of the appropriate anions. The NMR, MS, and CV data underscore the remarkable metallapentacycle stability despite the angle strain inherent in pentagons formed by octahedral metal ions. The low anion activation energies of encapsulation (ΔG(‡) ~ 50 kJ/mol) suggest that anion-π contacts assist the anion templation. We also studied reactions of Ag(I)X (X(-) = [PF6](-), [AsF6](-), [SbF6](-), [BF4](-)) with bptz or bppn (3,6-bis(2-pyridyl)-1,2-pyridazine) to assess the effect of the ligand π-acidity on the preferred structures. The X-ray data revealed that the higher π-acidity of the tetrazine ring in bptz leads to propeller-type products [Ag2(bptz)3](2+) exhibiting prominent short anion-π contacts. By contrast, the less π-acidic bppn preferentially favors grids [Ag4(bppn)4](4+) which exhibit maximized π-π interactions. Finally, we explored the reactions of the extended π-acidic heterocycle HAT(CN)6 (1,4,5,8,9,12-hexaazatriphenylene-hexacarbonitrile) with the Cl(-), Br(-), I(-) ions which lead to highly colored solutions/crystals. X-ray crystallographic studies of the HAT(CN)6/halide complexes revealed unprecedented multisite short peripheral charge-transfer and centroid anion-π contacts. In solution, the charge-transfer contacts were evidenced by electronic absorption, (13)C and halogen NMR, as well as MS data. The distinctly colored complex entities exhibit extraordinarily high association constants, which render them promising for anion-sensing receptor applications.

Synthesis and study of tetramethylammonium hexafluoridozirconate and hexafluoridohafnate solvated by H2O·HF adducts and [N(CH3)4]2ZrF6

A new type of zirconium and hafnium fluoride complexes of the composition [N(CH3)4]2AF6·(H2O·HF) (A=Zr, Hf) solvated by H2O·HF adducts and the compound [N(CH3)4]2ZrF6 have been synthesized. The synthesized compounds were studied by X-ray diffraction, vibrational spectroscopy, quantum chemical calculations and differential thermal analysis. The crystal structures of [N(CH3)4]2AF6·(H2O·HF) (A=Zr, Hf) are built up from N(CH3)4+ cations, octahedral complex anions [AF6]2−, and solvate adducts H2O·HF linked by strong hydrogen bonds FH⋯O. The compound [N(CH3)4]2ZrF6 is built up from N(CH3)4+ cations and complex anions [ZrF6]2−. In the investigated structures, the complex anions, cations, and adducts are linked by ionic interactions and a branched system of hydrogen bonds OH⋯F and СH⋯F.

Buckling the equatorial anion plane: octahedral anion distortions in ferroic perovskites and related systems resolved via neutron diffraction

A framework for describing anion displacements from perfect octahedra in perovskites has been developed for use with neutron diffraction data sets. We describe the distortions as noncoplanar arrangements, or buckling, of oxygen ions in any central plane of the octahedron, ignoring the central cation. Nonplanar distortions of octahedra have been calculated for perovskite structures contained within the Inorganic Crystal Structure Database. We find that antiferroelectric materials have buckling angles larger than ~2° and ferroelectric materials have buckling angles between 0° and 1°. The trend is found as a function of solid solution composition and temperature for common antiferroelectrics. For example, the described method resolves a structural difference between the end members PbTiO(3) and PbZrO(3), which exhibit ferroelectric and antiferroelectric responses, respectively. This technique is applicable to other structures containing anion octahedra, e.g., pyrochlores, spinels, and tungsten bronzes.

First example of bidentate coordination of the octahedral rhenium(III) cluster anion to a 3d-transition metal ion: Assembly of 2D coordination network [{Cu(NH3)3}2{Re6S8(OH)4(μ-OH)2}]·8H2O

A new 2D coordination polymer, [{Cu(NH3)3}2{Re6S8(OH)4(μ-OH)2}]·8H2O (1), has been prepared as a result of reactivity studies of the octahedral rhenium cluster anion [Re6S8(OH)6]4− in a system containing Cu2+ cations in aqueous ammonia. The compound was characterized by means of IR spectroscopy, thermal analysis, elemental analysis and single-crystal X-ray diffraction analysis. The structure determination revealed the presence of neutral layers containing Cu2+ cations surrounded by three NH3 molecules, located midway between two different [Re6S8(OH)6]4− cluster anions. The cluster anion displays an unprecedented bidentate coordination to Cu2+, occurring via the μ3-S ligand (Cu⋯S, 2.996(3)Å) and O atom of a terminal OH group (Cu–O, 1.986(7)Å). The resultant Cu(II) coordination environment can be described as a stretched octahedral geometry (4+2).

Anion–π Interactions Involving [MXn]m−Anions: A Comprehensive Theoretical Study

In this manuscript we perform a systematic study on the geometric and energetic features of anion-π complexes, wherein the anion is a metal complex of variable shapes and charges. Such a study is lacking in the literature. For the calculations we used the ab initio RI-MP2/def2-TZVPP level of theory. A search in the Cambridge Structural Database (CSD) provides the experimental starting point that inspired the subsequent theoretical study. The influence of [MX(n)](m-) on the anion-π interaction was analyzed in terms of energetic, geometric, and charge transfer properties and Bader's theory of "atom-in-molecules" (AIM). The binding energy depends on the coordination index, geometric features and different orientations adopted by the metallic anion. The binding mode resembling a stacking interaction for linear, trigonal planar and square-planar anions is the most favorable. For tetrahedral and octahedral anions the most favorable orientation is the one with three halogen atoms pointing to the ring.

Synthesis, crystal structure, vibrational properties and dielectric properties of 1-(2-ammonium-ethyl) pipérazindiium hexachlorobismuthate(III)

[C6H18N3]BiCl6 crystallizes at room temperature in the monoclinic space group P21/n. The crystal is built up of separated BiCl63− octahedral anions and 1-(2ammonium-ethyl) piperazindiium cations. Differential scanning calorimetry (DSC) disclosed structural phase transitions of the order–disorder type at 343 and 393K. Dielectric investigations revealed a step-wise change of the electric permittivity at Ttr1 and Ttr2, characteristic of crystals in the high-temperature phase. Temperature-dependant Raman spectra for polycrystalline samples were taken between 298 and 493K to clarify the cation dynamics contribution to the mechanism of the phase transition. The modes are assigned to the deformation vibrations of the anionic group and NH+, NH2+ and NH3+ groups in the 1-(2ammonium-ethyl) piperazindiium cations. The 1-(2ammonium-ethyl) piperazindiium cations appeared to be the most sensitive to the phase transition.

Radical cation salts of CLEDO‐TTF with octahedral anions

AbstractA new π‐donor, 4‐chloro‐4′,5′‐ethylenedioxytetrathiafulvalene (CLEDO‐TTF) was synthesized from 4‐methoxycarbonyl‐4′,5′‐ethylenedioxytetrathiafulvalene in the yield of 85%. In the crystal of neutral molecule, the head‐to‐head type uniform stacking column, in which the donor molecules are related by a unit cell translation, was formed. The electrocrystallization of CLEDO‐TTF with PF6 afforded two kinds of 1:1 salts of purple rods and green plates as miner species. In both 1:1 salts, the head‐to‐tail dimers with ring‐over‐ring overlapping mode were formed. Geometrically, the dimers were included in slipped stacking column in the purple rod salt, while the two‐dimensional network was formed in the green plate salt. The significant steric effect of chlorine atom along the molecular long axis was confirmed by the intermolecular arrangement in the green plate salt, in which the chlorine atom is faced to the hydrogen atom of the neighbouring donor along the long axis. The normal mode analyses were carried out for the neutral and monocationic CLEDO‐TTF, which agreed well with the observed Raman spectra. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

77Se-NMR study of quasi-one dimensional organic conductor (TMTSF)2X

Quasi-one dimensional organic conductor (TMTSF)2X with octahedral anions X = PF6, AsF6, and SbF6 have been studied by NMR measurements at the Se-sites which are substantially responsible for conductivity in this system. Close resemblances in the temperature dependence of the spin-lattice relaxation rate 1/T1 and the evolution of internal field in the SDW state were observed in the three measured compounds. The existence of the sub-phases in the SDW phase of all these compounds, which is evidenced by T1 but not from spectrum measurements, indicates that this is a common feature among (TMTSF)2X system with an incommensurate SDW wave number and is associated with dynamic property rather than static one.