Table of Contents

Abstract: A gate-induced thermally stimulated current (TSC) on β′-(BEDT-TTF)(TCNQ) crystalline FET were conducted to elucidate the previously observed ferroelectric-like behaviors. TSC which is symmetric for the polarization of an applied V^P_G and has a peak at around 285 K was assigned as a pyroelectric current. By integrating the pyroelectric current, temperature dependence of the remnant polarization charge was obtained and the existence of the ferroelectric phase transition at 285 K was clearly demonstrated. We have tentatively concluded that the phase transition between dimer Mott insulator and charge ordered phase occurred at around the interface of organic crystal and substrate.

Abstract: Heat capacity measurements of κ-(BEDT-TTF)₂X (BEDT-TTF: Bis(ethylendithio) tetrathiafulvalene, X: counteranions) which are classified as two-dimensional (2D) dimer-Mott system are reported. At first, we explain structural and electronic features originated from rigid dimerization in donor arrangement in 2D layers. The antiferromagnetic Mott insulating phase located at low-pressure region in the phase diagram shows vanishing γ electronic heat capacity coefficient in the heat capacity, which claims opening of a charge-gap in this insulating state. Then, a systematic change of the γ around the Mott boundary region is reported in relation to the glass freezing of ethylene dynamics. The thermodynamic parameters determined by ∆C_p/γT_c of 10 K class superconductors, κ-(BEDT-TTF)₂Cu(NCS)₂ and κ-(BEDT-TTF)₂Cu[N(CN)₂]Br demonstrate that a rather large gap with a strong coupling character appears around the Fermi-surface. On the other hand, the low temperature heat capacity clearly shows a picture of nodal-gap structure due to an anisotropic pairing. The comparison with lower T_c compounds in the κ-type structure is also performed so as to discuss overall features of the κ-type superconductors. The heat capacity measurements of hole-doped systems containing mercury in the counteranions show an anomalous enhancement of γ, which is consistent with the T₁⁻¹ of NMR experiments etc. The results of heat capacity measurements under high pressures are also reported.

Abstract: This paper is an overview concerning the preparations and properties as well as possible applications of neutral (one component) metal 1,2-dithiolenes (and selenium analogues). The structural, chemical, electrochemical, optical and electrical behavior of these complexes depend strongly on the nature of ligand and/or the metal. The results of unsymmetrical in comparison to those of symmetrical complexes related to the properties of materials in the solid state are primarily discussed. The optical absorption spectra exhibit strong bands in the near IR spectral region ca. 700 to ca. 1950 nm. X-ray crystal structure solutions show that the complexes usually have square-planar geometry with S–S and/or M–S contacts. Some of them behave as semiconductors or conductors (metals) and are stable in air. The cyclic voltammograms at negative potentials are different from the corresponding potentials of tetrathiafulvalenes (TTFs). As a consequence, the LUMO bands occur at much lower levels than those of TTFs. Consequently, electrical measurements under conditions of field effect transistors exhibit n-type or ambipolar behavior. Illumination of materials with high power lasers exhibits non-linear optical behavior. These properties enable metal 1,2-dithiolene complexes to be classified as promising candidates for optical and electronic applications, (e.g., saturable absorbers, ambipolar inverters).

Abstract: Organic molecular conductors with a strongly correlated electron system, in which the itinerancy of electrons (or holes) and the electron correlation (U/W, U, the on-site Coulomb repulsion, W, the bandwidth) compete with each other, are promising candidates for achieving superconductivity and also for exploring remarkable physical properties induced by external stimuli such as pressure, light, voltage and current. Our synthetic approach to the construction of strongly correlated organic electron systems is based on chemical modifications to the donor molecule BDH-TTP [2,5-bis(1,3-dithiolan-2-ylidene)-1,3,4,6-tetrathiapentalene] capable of producing metallic CT (charge-transfer) salts stable down to low temperatures (4.2–1.5 K). This aims at enhancing the electron correlation in the itinerant electron system by decreasing the bandwidth. Chemical modifications of BDH-TTP such as ring expansion of two outer dithiolane rings, replacement of one sulfur atom in an outer dithiolane ring with an oxygen atom and introduction of two methyl substituents into an outer ditiolane ring led to BDA-TTP [2,5-bis(1,3-dithian-2-ylidene)-1,3,4,6-tetrathiapentalene], DHOT-TTP [2-(1,3-dithiolan-2-ylidene)-5-(1,3-oxathiolan-2-ylidene)-1,3,4,6-tetrathiapentalene] and DMDH-TTP [2-(4,5-dimethyl-1,3-dithiolan-2-ylidene)-5-(1,3-dithiolan-2-ylidene)-1,3,4,6-tetrathiapentalene], respectively. In this review, the physical properties and the crystal and electronic structures of molecular conductors derived from these donor molecules will be described.

Abstract: Hydrogen desorption from hydride matrix is still an open field of research. By means of accurate first-principle molecular dynamics (MD) simulations an Mg–MgH2 interface is selected, studied and characterized. Electronic structure calculations are used to determine the equilibrium properties and the behavior of the surfaces in terms of structural deformations and total energy considerations. Furthermore, extensive ab-initio molecular dynamics simulations are performed at several temperatures to characterize the desorption process at the interface. The numerical model successfully reproduces the experimental desorption temperature for the hydride.

Abstract: An isostructural series of anion radical salts, β'-(Et_xMe_4−xZ)[Pd(dmit)₂]₂ (x = 0–2, Z = P, As, Sb), with a quasi-triangular lattice comprising the dimer unit [Pd(dmit)₂]₂⁻ belong to a strongly correlated electron system with geometrical frustration. Intra and interdimer transfer integrals between the frontier molecular orbitals, which characterize the strength of electron correlation and degree of frustration, can be tuned by selection of the counter cation. We have systematically analyzed the crystal structure with X-ray diffraction method and intermolecular transfer integrals using extended Hückel molecular orbital calculations based on structural data. The variation in the cation affects the unit cell in a manner equivalent to an anisotropic pressure. Increasing the covalent radius of the central atom Z and the number of ethyl groups (x) in the cation leads to slight arching of the Pd(dmit)₂ molecule. This arch-shaped distortion of the Pd(dmit)₂ molecule modifies the interdimer transfer integrals in formation of the regular triangular dimer lattice. On the other hand, the intradimer transfer integral, which is correlated with the effective on-site Coulomb interaction of the dimer, is weakly dependent on the type of cation.

Abstract: Molecular solids are generally highly insulating. The creation of conducting molecular solids proved to be a major scientific challenge. As in the case of Si technology, the challenge started as impurity doping in band insulators and then developed into highly doped polymers, which are not crystalline. More conducting materials in crystalline forms have been realized in charge transfer (CT) complexes with two different kinds of molecules, where electrons are transferred between them in solids. In such CT complexes, not only conducting, but also even superconducting systems were achieved in 1980 and today more than 100 different superconductors are known. The most remarkable achievement in this direction was the realization of a truly metallic state in molecular solids based on a single kind of molecule. These are called single component molecular metals (SCMM) and consist of a rich variety of electronic properties. In these conducting molecular solids, CT and SCMM, many interesting electronic properties resulting from mutual Coulomb interactions and electron-phonon interactions have been explored so far, and these will be reviewed briefly in this article from a theoretical viewpoint. Challenges to come, based on these achievements, are also discussed at the end of this review.

Abstract: The relationship between the conducting behavior and the degree of charge fluctuation in the β″-type BEDT-TTF salts is reviewed from the standpoints of vibrational spectroscopy and crystal structure. A group of β″-type ET salts demonstrates the best model compounds for achieving the above relationship because the two-dimensional structure is simple and great diversity in conducting behavior is realized under ambient pressure. After describing the requirement for the model compound, the methodology for analyzing the results of the vibrational spectra is presented. Vibrational spectroscopy provides the time-averaged molecular charge, the charge distribution in the two-dimensional layer, and the inter-molecular interactions, etc. The experimental results applied to 2/3-filled and 3/4-filled β″-type ET salts are reported. These experimental results suggest that the conducting property, the difference in the time-averaged molecular charges between the ionic and neutral-like sites, the alternation in the inter-molecular distances and the energy levels in the charge distributions are relevant to one another. The difference in the time-averaged molecular charges, ∆ρ, is a useful criterion for indicating conducting behavior. All superconductors presented in this review are characterized as small but finite ∆ρ.

Abstract: The one-pot synthesis of a Cu(II) complex with partially oxidized tetrathiafulvalene (TTF) moieties in its capping MT-Hsae-TTF ligands, [Cu^II(MT-sae-TTF)₂] [Cu^ICl₂] was realized by the simultaneous occurrence of Cu(II) complexation and Cu^IICl₂ mediated oxidation of TTF moieties. The crystal structure was composed of one-dimensional columns formed by partially oxidized TTF moieties and thus the cation radical salt showed relatively high electrical conductivity. Tight binding band structure calculations indicated the existence of a Peierls gap due to the tetramerization of the TTF moieties in the one-dimensional stacking column at room temperature, which is consistent with the semiconducting behavior of this salt.

Abstract: Electrolysis of Na and K salts of the anion dicyano(phthalocyaninato)cobalt(III) (Co(Pc)(CN)₂) in ethanol yields one-dimensional partially oxidized salts of A[Co(Pc)(CN)₂]₂.4(EtOH) (A = Na and K). The cationic component is the supramolecular cation [A(EtOH)₄]⁺, which forms hydrogen bonds with the CN ligands of the Co(Pc)(CN)₂ units. The crystal shows metallic conductivity, in contrast to the thermally activated conductivity observed in the isomorphous tetraphenylphosphonium (TPP) salt of TPP[Co(Pc)(CN)₂]₂. Since the π-π interactions in these isomorphous crystals are nearly the same, the distinctive behavior of the Na and K salts may be attributed to the difference in the degree of charge disproportionation in these crystals.

Abstract: The crystal structure of the coordination polymer diaqua(μ-5,5'-bistetrazolato-κ⁴N¹,N²,N⁵,N⁶)copper(II) was determined by X-ray diffraction. The copper atoms are connected to chains over the bridging 5,5'-bistetrazolato ligand. The energetic properties of the compound were investigated, such as thermal behavior and sensitivities (shock, friction, electrical spark).

Abstract: A facile one-pot synthesis of methyl 5-(4-chlorobenzoyloxy)-1-phenyl-1H-pyrazole-3-carboxylate (4) is described. The title compound was efficiently synthesized by the reaction of phenyl hydrazine, dimethyl acetylenedicarboxylate and 4-chlorobenzoyl chloride in dichloromethane under reflux in good yield. The structure of the target compound was deduced by modern spectroscopic and analytical techniques and unequivocally confirmed by a single crystal X-ray diffraction analysis. The crystal of the title compound belongs to orthorhombic system, space group P 2₁ 2₁ 2₁ with cell parameters a = 6.6491(3) Å, b = 7.9627(6) Å, c = 30.621(5) Å, α = β = γ = 90° and Z = 4. The crystal packing of the compound (4) is stabilized by an offset π-stacking between the planar benzoyl-substituted diazole moieties.

Abstract: The crystal structures of two zincophosphate networks prepared in the presence of 1,5-diaminopentane (dap) are described. In Zn₃(PO₄)₂(C₅H₁₄N₂)₂·3H₂O (1) the dap forms Zn–N coordinate bonds to generate an unusual three-dimensional “hybrid” framework constructed from ZnO₃N, ZnO₂N₂ and PO₄ tetrahedra with three different types of elongated channels occupied by water molecules. In C₅H₁₆N₂·Zn₃(PO₄)₂(HPO₄)·H₂O; (2) the doubly-protonated H₂dap acts in a more typical way to template double layers of vertex-sharing ZnO₄, PO₄ and HPO₄ tetrahedra incorporating 10-rings and interacts with the inorganic component via N–H O hydrogen bonds. Crystal data: 1 (C₁₀H₃₄N₄O₁₁P₂Zn₃), M_r = 644.46, monoclinic, C2 (No. 4), Z = 4, a = 25.302 (7) Å, b = 4.9327 (13) Å, c = 19.808 (6) Å, b = 107.377 (8)°, V = 2359.4 (12) ų, R(F) = 0.054, wR(F²) = 0.139. 2 (C₅H₁₉N₂O₁₃P₃Zn₃), M_r = 604.24, monoclinic, P2₁/c (No. 14), Z = 4, a = 11.3275 (15) Å, b = 8.3235 (11) Å, c = 18.588 (2) Å, b = 96.979 (3)°, V = 1739.6 (4) ų, R(F) = 0.056, wR(F²) = 0.119.

Abstract: Quasi-two-dimensional organic conductor λ-BETS₂FeCl₄ (BETS = bis(ethylenedithio)tetraselenafulvalene) transforms from a paramagnetic metal (PM) to an antiferromagnetic insulator (AFI) at a transition temperature, T_MI, of 8.3 K under zero magnetic field. To understand the mechanism of this PM-AFI phase transition, we studied the thermodynamic properties of λ-BETS₂FeCl₄. We observed, below T_MI, a six-level Schottky hump in its specific heat and a broad shoulder in its magnetic susceptibility. Just below the transition temperature T_MI, about 80% of 3d spin degree of freedom is sustained. These temperature dependences clarify that π and 3d spins do not cooperatively form the AF order at T_MI. In λ-BETS₂Fe_xGa_1−xCl₄ system, the increasing Fe 3d spin density enhances the internal magnetic field caused by π spin antiferromagnetic (AF) ordering, although the 3d spin itself maintains large entropy against the AF ordering. It was confirmed that the Fe 3d spin provided favorable conditions for this mysterious PM-AFI phase transition in the π electron system. We propose that this phase transition originates from the magnetic anisotropy introduced by the π-d interaction, which suppressed the low dimensional fluctuation in the π spin system.

Abstract: A review is given for recent theoretical studies on phase transitions in quasi-one-dimensional molecular conductors with a quarter-filled band. By lowering temperature, charge transfer salts exhibit a variety of transitions accompanying symmetry breaking, such as charge ordering, lattice dimerization, antiferromagnetic transition, spin-Peierls distortion, and so on. Analyses on microscopic quasi-one-dimensional models provide their systematic understandings, by the complementary use of different analytical and numerical techniques; they can reproduce finite-temperature phase transitions, whose results can be directly compared with experiments and give feedbacks to material design.

Abstract: The crystal structures of 2,4,5-tribromo-1-(prop-2-ynyl)imidazole and seven new 1,3-dialkyl-2,4,5-tribromoimidazolium salts (R¹ = propenyl, propynyl, dibromopropenyl; R² = Me, Et) with halogen-containing anions (tetrafluoroborate, hexafluorophosphate, triflimide) were determined. The structures revealed halogen...halogen and anion...π interactions. Contacts of the type Br...Br, Br...F, Br...O, Br...N, F...F, H...Br, H...F, F...π and O...π were identified. Specific interactions were quantified by Hirshfeld surface analysis.

Abstract: Quasi-One and quasi-two dimensional organic conductors consisting of TTF derivatives such as BEDT-TTF (bis-(ethylene-dithio)-tetra-thia-fulvalene) and TMTCF (C = S; TMTTF: tetra-methyl-tetra-thia-fulvalene, C = Se; TMTSF: tetra-methyl-tetra-selena-fulvalene) have been well investigated in condensed matter physics because of interest in the emerging electric and magnetic properties, such as the spin density wave, charge order, superconductivity, anti-ferromagnetism, and so on. To probe the electronic state, nuclear magnetic resonance (NMR) is one of the most powerful tools as the microscopic magnetometer. A number of ¹³C-NMR studies have been performed of the double-site central ¹³C=¹³C bond substituted molecules. However, problems with the coupled spin system of ¹³C=¹³C complicated the interpretation for observations on NMR. Therefore, single-site ¹³C-enriched molecules are desired. We summarize the problem of Pake doublet and the preparation of the single-site ¹³C-susbstituted BEDT-TTF and TMTCF molecules. We also demonstrate the superiority of ¹³C-NMR of the single-site ¹³C-susbstituted molecule utilizing the hyperfine coupling tensor.

Abstract: The crystal and molecular structures of two 2-aminothiophene derivatives, potential allosteric enhancers at the human A₁ adenosine receptor, are reported. (2-Amino-4,5,6,7-tetrahydro-1-benzothiophen-3-yl)(phenyl)methanone (1) crystallizes in the orthorhombic space group Pna2₁ (a = 9.2080(4) Å, b = 14.0485(7) Å, c = 10.3826(6) Å), and (2-amino-5-ethylthiophen-3-yl)(2-chlorophenyl)methanone (2) crystalizes in the monoclinic P2₁/c space group with unit cell parameters a = 10.6092(8) Å, b = 10.8355(8) Å, c = 11.1346(9) Å, β = 98.643(6)Å. In both molecules the intramolecular N–H···O=C hydrogen bonds close six-membered planar rings and significantly influence the molecular conformation. Intermolecular N–H···O bonds connect the molecules in infinite chains along a in case of 1, and along b in 2; in each case the appropriate unit cell axis is approximately 10 Å long.

Abstract: Strongly electron-lattice- and electron-electron-correlated molecular crystals, such as charge transfer (CT) complexes, are often sensitive to external stimuli, e.g., photoexcitation, due to the cooperative or competitive correlation of various interactions present in the crystals. These crystals are thus productive targets for studying photoinduced phase transitions (PIPTs). Recent advancements in research on the PIPT of CT complexes, especially Et₂Me₂Sb[Pd(dmit)₂]₂ and (EDO-TTF)₂PF₆, are reviewed in this report. The former exhibits a photoinduced insulator-to-insulator phase transition with clearly assigned spectral change. We demonstrate how to find the dynamics of PIPT using this system. The latter exhibits a photoinduced hidden state as an initial PIPT process. Wide energy ranged time-resolved spectroscopy can probe many kinds of photo-absorption processes, i.e., intra-molecular and inter-molecular electron excitations and intramolecular and electron-molecular vibrations. The photoinduced spectral changes in these photo-absorption processes reveal various aspects of the dynamics of PIPT, including electronic structural changes, lattice structural changes, and molecular deformations. The complexities of the dynamics of the latter system were revealed by our measurements.

Abstract: The synthesis, structure and properties of the bimetallic layered coordination polymer, [KDy(C₈H₃NO₆)₃(C₈H₅NO₆)]_n·2n(C₁₀H₉N₂)·5n(H₂O) = [KDy(Hptc)₃(H₃ptc)]_n·2n(Hbipy)·5n(H₂O), are described. The Dy³⁺ ion is coordinated by three O,N,O-tridentate doubly-deprotonated pyridine tri-carboxylate (Hptc) ligands to generate a fairly regular DyO₆N₃ tri-capped trigonal prism, with the N atoms acting as the caps. The potassium ion is coordinated by an O,N,O-tridentate H₃ptc molecule as well as monodentate and bidentate Hptc ligands to result in an irregular KNO₉ coordination geometry. The ligands bridge the metal-atom nodes into a bimetallic, layered, coordination polymer, which extends as corrugated layers in the (010) plane, with the mono-protonated bipyridine cations and water molecules occupying the inter-layer regions: Unlike related structures, there are no dysprosium–water bonds. Many O–HLO and N–HLO hydrogen bonds consolidate the structure. Characterization and bioactivity data are described. Crystal data: C₅₂H₄₂DyKN₈O₂₉, M_r = 1444.54, triclinic, (No. 2), Z = 2, a = 9.188(2) Å, b = 15.7332(17) Å, c = 19.1664(19) Å, α = 92.797(6)°, β = 92.319(7)°, γ = 91.273(9)°, V = 2764.3(7) ų, R(F) = 0.029, wR(F²) = 0.084.

Abstract: Bis-fused donors composed of (thio)pyran-4-ylidene-1,3-dithiole and tetraselenafulvalene (1a, 2a) and their bis(methylthio) derivatives (1b, 2b) were synthesized. Cyclic voltamograms of all the donors consisted of four pairs of one-electron redox waves, and it was suggested that a positive charge of 1^+• and 2^+• distributed mainly on the (thio)pyran-4-ylidene-1,3-dithiole moiety. X-ray structure analysis revealed that (1b)PF₆(C₆H₅Cl)_0.5 and (2b)PF₆(C₆H₅Cl) formed one-dimensional conducting stacks in which the donors were dimerized or tetramerized. In those salts, intramolecular charge disproportionation of the donors was suggested by X-ray structure analysis and density functional theory (DFT) calculation with UB3LYP/6-31G(d) basis function. A tight-binding band calculation suggested that these materials were band insulators. All the donors gave highly conducting TCNQ (7,7,8,8-tetracyanoquinodimethane) complexes and I₃⁻ salts (σ_rt = 0.3–19 S cm⁻¹ on a compressed pellet) with very low activation energies of 0.017–0.040 eV, while single crystals of (1b)PF₆(C₆H₅Cl)_0.5 and (2b)PF₆(C₆H₅Cl) exhibited semiconductive behavior with large activation energies (E_a = 0.16–0.22 eV).

Abstract: Two new pyrazoline derivatives, 3,5-bis(4-fluorophenyl)-4,5-dihydropyrazole-1-carboxamide (1) and 3,5-bis(4-fluorophenyl)-4,5-dihydropyrazole-1-carbothioamide (2), were synthesized by reacting 4,4'-difluoro chalcone with semicarbazide hydrochloride and thiosemicarbazide in ethanolic sodium hydroxide solution. Both the compounds were confirmed by single crystal X-ray diffraction data and supported by IR, NMR, and mass spectral data. In 1, crystal packing is stabilized by N–H…O hydrogen bonds and weak N–H...N, N–H…F and C–H…F intermolecular interactions. In 2, only weak N–H…F and N–H…S intermolecular interactions are observed. Crystal data: C₁₆H₁₃F₂N₃O, (1), M_r = 301.29, monoclinic, C2/c, a = 17.6219(6) Å, b = 10.8735(3) Å, c = 15.3216(5) Å, β = 102.864(3)°, V = 2862.11(16) ų, Z = 8, T = 173 K, R(F) = 0.0511, wR(F²) = 0.1333; C₁₆H₁₃F₂N₃S, (2), M_r = 317.35, monoclinic, P2₁/c, a = 14.339(2) Å, b = 11.1478(17) Å, c = 9.541(2)(5) Å, β = 107.007(18)°, V = 1458.5(5) ų, Z = 4, T = 173 K, R(F) = 0.0413, wR(F²) = 0.0959.

Abstract: ¹H and ¹⁹⁵Pt NMR are used to probe the spin ½ anion chain in the quasi-one-dimensional conductor Per₂[Pt(mnt)₂], which exhibits nearly simultaneous charge density wave (CDW) and spin-Peierls (SP) transitions at low temperatures (T_c ~ 8 K). Below T_c the [Pt(mnt)₂] chain forms a spin-singlet state that is evident in ¹H NMR spectra and spin relaxation (1/T₁) rates; however minority unpaired Pt spins may remain in the SP ground state. With increasing magnetic field, the SP and CDW order parameters decrease in unison, indicating they are coupled up to a critical field B_c ~ 20 T. Above B_c, the spin singlet evolves into a spin-polarized configuration. The ¹⁹⁵Pt NMR signals vanish as either T_c or B_c are approached from within the SP ground state, suggesting the hyperfine field of the Pt nucleus is significantly stronger than at the proton sites. Simulations yield a consistent picture of the angular, temperature, and magnetic field-dependent spectral features.

Abstract: Single crystals and phase pure samples of oxygen-poor ternary lanthanide oxide selenides with the composition M₁₀OSe₁₄ (M = La–Nd; tetragonal, I4₁/acd; a = 1592.0–1559.8 pm, c = 2106.5–2062.9 pm) could be obtained by reacting the corresponding metals, selenium and selenium dioxide as oxygen source. Their crystal structures are isotypic with Pr₁₀OS₁₄ and thus contain isolated [OM₄]¹⁰⁺ tetrahedra (d(O^2––M³⁺) = 243–248 pm) embedded in a complex anionic {[M₆Se₁₄]^10–} lanthanide selenide matrix (d(M³⁺–Se^2–) = 288–358 pm). All three crystallographically independent M³⁺ cations exhibit eight contacts to chalcogenide anions (O^2– and/or Se^2–) resulting in the formation of bicapped trigonal prismatic coordination polyhedra. The optical band gaps of the oxide selenides M₁₀OSe₁₄ amount to values between 1.89 and 2.04 eV indicating wide band-gap semiconductors.

Abstract: The crystal structure of APA₂[Zn₃(HPO₄)₄(H₂O)₂] (APA = 2-amino-1-phenylene-ammonium, C₆H₉N₂⁺) (1), as prepared by a predominantly non-aqueous synthesis, is described and compared to related compounds. 1 is built up from an alternating array of ZnO₄ and HPO₄ tetrahedra sharing vertices as Zn–O–P bonds to generate infinite anionic sheets. Within these sheets, polyhedral 4-, 6- and 8-rings are apparent. The negative charge of the inorganic layer is balanced by singly-protonated APA template cations and water molecules are also present. The components are linked by N_t–H⋯O_f, O_f–H⋯O_w, O_w–H⋯O_f and O_f–H⋯N_t (t = template, f = framework, w = water) hydrogen bonds: the last of these represents an unusual framework-to-template interaction. Weak C_t–H⋯O_f links may also play a role in consolidating the structure. Crystal data: 1 (C₁₂H₂₆N₄O₁₈P₄Zn₃), M_r = 834.36, monoclinic, C2/c (No. 15), Z = 4, a = 20.194 (8) Å, b = 8.682 (3) Å, c = 15.123 (6) Å, β = 91.510 (11)°, V = 2650.5 (17) ų, R(F) = 0.048, wR(F²) = 0.112.

Abstract: Two-dimensional quarter-filled organic solids are a promising class of materials to realize the strongly correlated insulating states called dimer Mott insulator and charge order. In their conducting layer, the molecules form anisotropic triangular lattices, harboring geometrical frustration effect, which could give rise to many interesting states of matter in the two insulators and in the metals adjacent to them. This review is concerned with the theoretical studies on such issue over the past ten years, and provides the systematic understanding on exotic metals, dielectrics, and spin liquids, which are the consequences of the competing correlation and fluctuation under frustration.

Abstract: The conversion of Z-phenylalanine hydrazide with cyanogen bromide resulted in the formation of the corresponding 2-amino-1,3,4-oxadiazole by spontaneous cyclization of the intermediary cyanohydrazide. The molecular structure of the product was confirmed by single crystal X-ray diffraction. Crystals of the title compound where obtained from a saturated solution in a mixture of petroleum ether and ethyl acetate and belong to the monoclinic space group P2₁ with unit cell parameters a = 9.8152(2) Å, b = 9.6305(2) Å, c = 9.8465(2) Å, β = 116.785(1)°. The asymmetric unit contains one molecule.

Abstract: We have studied the electronic structure of Cu(tmdt)₂, a material related to single-component molecular conductors, by first-principles calculations. The total energy calculations for several different magnetic configurations show that there is strong antiferromagnetic (AFM) exchange coupling along the crystal a-axis. The electronic structures are analyzed in terms of the molecular orbitals near the Fermi level of isolated Cu(tmdt)₂ molecule. This analysis reveals that the system is characterized by the half-filled pdσ(−) band whose intermolecular hopping integrals have strong one-dimensionality along the crystal a-axis. As the exchange splitting of the band is larger than the band width, the basic mechanism of the AFM exchange coupling is the superexchange. It will also be shown that two more ligand orbitals which are fairly insensitive to magnetism are located near the Fermi level. Because of the presence of these orbitals, the present calculation predicts that Cu(tmdt)₂ is metallic even in its AFM state, being inconsistent with the available experiment. Some comments will be made on the difference between Cu(tmdt)₂ and Cu(dmdt)₂.

Abstract: Tetrathiafulvalene (TTF), pentacene, and quarterthiophene with tert-butyl substituents are synthesized, and the crystal structures and the transistor properties are investigated. The tetracyanoquinodimethane (TCNQ) complex of tert-butyl TTF constructs highly one-dimensional segregated columns with tetragonal crystal symmetry.

Abstract: The crystal and molecular structures of the title compounds, ethyl 4-(4-hydroxyphenyl)-6-(6-methoxy-2-naphthyl)-2-oxocyclohex-3-ene-1-carboxylate (I) and ethyl 4-(3-bromophenyl)-6-(6-methoxy-2-naphthyl)-2-oxocyclohex-3-ene-1-carboxylate (II), are reported and confirmed by single crystal X-ray diffraction data. Compound (I), C₂₆H₂₄O₅, crystallizes from a methanol solution in the monoclinic C2/c space group with eight molecules in the unit cell. The unit cell parameters are: a = 25.4114(5) Å, b = 8.47440(10) Å, c = 20.6921(4) Å, β = 108.328(2)° and V = 4229.92(13) ų. Disorder is observed throughout the entire molecule with an occupancy ratio 0.690(2):0.310(2). Compound (II), C₂₆H₂₃O₄Br, crystallizes from an ethyl acetate solution in the monoclinic P2₁/c spacegroup with four molecules in the unit cell. The unit cell parameters are a = 17.8991(9) Å, b = 11.4369(6) Å, c = 10.8507(5) Å, β = 92.428(4)° and V = 2219.25(19) ų. Disorder is observed in the cyclohexenone ring and the carboxylate group with an occupancy ratio 0.830(6):0.170(6). Weak O–H...O (I) or C–H...O (II) intermolecular interactions are observed which influence crystal packing stability. These chalcone derivative types of molecules are important in their ability to act as activated unsaturated systems in conjugated addition reactions of carbanions in the presence of basic catalysts which exhibit a multitude of biological activities.

Abstract: The title compound, Methyl 5-Hydroxy-1-Phenyl-1H-Pyrazole-3-Carboxylate (C₁₁H₁₀N₂O₃), was prepared by a one-pot, two-component reaction of an equimolar mixture of phenyl hydrazine and dimethyl acetylene dicarboxylate (DMAD) at reflux temperature for 2 h in a mixture of toluene and dichloromethane as solvent. C₁₁H₁₀N₂O₃ was crystallized from an ethanol solution in monoclinic space group P2₁/c with unit cell dimensions a = 9.5408(16), b = 9.5827(16), c = 11.580(2) Å, β = 105.838(3)°, V = 1018.5(3) ų, Z = 4.

Abstract: The synthesis, structure and some properties of the one-dimensional coordination polymer, [Pr₂(pdc)₃(Hpdc)]_n·n(H3hp)·8n(H₂O), (H₂pdc = pyridine 2,6-dicarboxylic acid, C₇H₅NO₄; 3hp = 3-hydroxypyridine, C₅H₅NO) are described. One of the Pr³⁺ ions is coordinated by two O,N,O-tridentate pdc²⁻ ligands and one tridentate Hpdc⁻ anion to generate a fairly regular PrO₆N₃ tri-capped trigonal prism, with the N atoms acting as the caps. The second Pr³⁺ ion is coordinated by one tridentate pdc²⁻ dianion, four water molecules and two monodentate bridging pdc²⁻ ligands to result in a PrO₈N coordination polyhedron that approximates to a mono-capped square-anti-prism. The ligands bridge the metal-atom nodes into a chain, which extends in the [100] direction. The H3hp⁺ cation and uncoordinated water molecules occupy the inter-chain regions and an N–HLO and numerous O–HLO hydrogen bonds consolidate the structure. The H3hp⁺ species appears to intercalate between pendant pdc rings to consolidate the polymeric structure. Crystal data: 1 (C₃₃H₄₃N₅O₂₉Pr₂), M_r = 1255.54, triclinic, (No. 2), Z = 2, a = 13.2567(1) Å, b = 13.6304(2) Å, c = 13.6409(2) Å, α = 89.695(1)°, β = 63.049(1)°, γ = 86.105(1)°, V = 2191.16(5) ų, R(F) = 0.033, wR(F²) = 0.084.

Abstract: An approach to various metal hydrides based on electronic principles is presented. The effective medium theory (EMT) is used to illustrate fundamental aspects of metal-hydrogen interaction and clarify the most important processes taking place during the interaction. The elaboration is extended using the numerous existing results of experiment and calculations, as well as using some new material. In particular, the absorption/desorption of H in the Mg/MgH₂ system is analyzed in detail, and all relevant initial structures and processes explained. Reasons for the high stability and slow sorption in this system are noted, and possible solutions proposed. The role of the transition-metal impurities in MgH₂ is briefly discussed, and some interesting phenomena, observed in complex intermetallic compounds, are mentioned. The principle mechanism governing the Li-amide/imide transformation is also discussed. Latterly, some perspectives for the metal-hydrides investigation from the electronic point of view are elucidated.

Abstract: The compound τ-(P-S,S-DMEDT-TTF)₂(AuCl₂) (AuCl₂)_y (where P-S,S-DMEDT-TTF is the compound pyrazino-(S,S)-dimethyl-ethylenedithio-tetrathiofulvale) crystallizes in the non-centrosymmetric space group I-42d, with a = 7.3260(1) Å and c = 67.5487(12) Å (RT data) and remains tetragonal in the temperature range from RT to 100 K. This compound is a quasi-two-dimensional material and the relation of the lattice of the order part of the structure created by the donor molecules with that of the disordered anion lattice revealed by intense diffusion streaks give a value of y ≈ 0.9. In contrast to the Br and I analogs or the related compounds which contain the compound ethylenedioxy-S,S-dimethylenedithiotetrathiafulvalene (abbreviated as EDO-S,S-DMEDT-TTF) as donor and which exhibit anisotropic metallic behavior down to low temperature, this compound is anisotropic semiconductor in the same temperature range. The appearance of satellites on the diffraction images recorded below 110 K indicates a structural change. Resistivity measurements show that this material is a semiconductor with anisotropy σ_a/σ_c of ca. 400–1400 at room temperature.

Abstract: This paper reviews charge ordering in the organic conductors, β″-(BEDT-TTF) (TCNQ), θ-(BEDT-TTF)₂X, and α-(BEDT-TTF)₂X. Here, BEDT-TTF and TCNQ represent bis(ethylenedithio)tetrathiafulvalene and 7,7,8,8-tetracyanoquinodimethane, respectively. These compounds, all of which have a quarter-filled band, were evaluated using infrared and Raman spectroscopy in addition to optical conductivity measurements. It was found that β″-(BEDT-TTF)(TCNQ) changes continuously from a uniform metal to a charge-ordered metal with increasing temperature. Although charge disproportionation was clearly observed, long-range charge order is not realized. Among six θ-type salts, four compounds with a narrow band show the metal-insulator transition. However, they maintain a large amplitude of charge order (Δρ~0.6) in both metallic and insulating phases. In the X = CsZn(SCN)₄ salt with intermediate bandwidth, the amplitude of charge order is very small (Δρ < 0.07) over the whole temperature range. However, fluctuation of charge order is indicated in the Raman spectrum and optical conductivity. No indication of the fluctuation of charge order is found in the wide band X = I₃ salt. In α-(BEDT-TTF)₂I₃ the amplitude of charge order changes discontinuously from small amplitude at high temperature to large amplitude (Δρ_max~0.6) at low temperature. The long-range charge-ordered state shows ferroelectric polarization with fast optical response. The fluctuation of multiple stripes occurs in the high-temperature metallic phase. Among α-(BEDT-TTF)₂MHg(SCN)₄ (X = NH₄, K, Rb, Tl), the fluctuation of charge order is indicated only in the X = NH₄ salt. α′-(BEDT-TTF)₂IBr₂ shows successive phase transitions to the ferroelectric state keeping a large amplitude of charge order (Δρ_max~0.8) over the whole temperature range. It was found that the amplitude and fluctuation of charge order in these compounds is enhanced as the kinetic energy (bandwidth) decreases.

Abstract: 5-(2-Chlorophenyl)-7-ethyl-1H-thieno[2,3-e][1,4]diazepin-2(3H)-one, a close analogue of clotiazepam (full agonist at GABA receptor), crystallizes in monoclinic P2₁/c space group with a = 15.6941(6) Å, b = 10.7909(4) Å, c = 8.6586(3) Å, and β = 102.184(4)° (at 125 K). Seven-Membered diazepine ring has approximate mirror plane of symmetry, planar thieno and phenyl rings are almost perpendicular to one another, dihedral angle between their mean planes is 84.11(5)°. N–H···O hydrogen bonds connect molecules into centrosymmetric dimers which are further expanded into 3D crystal structure with the help of weaker C–H···O and C–H···π interactions. The methyl group is disordered at room temperature, but it gets gradually ordered at lower temperatures and becomes fully ordered at approximately 200 K. The changes in structure with temperature were studied between 125 and 380 K. The unit cell volume—as expected—increases almost monotonically when the temperature rises, but one of the parameters shortens significantly.

Abstract: Two dinuclear Cu^II complexes based on a diazecine ligand were characterized by X-ray diffraction, one of which includes the rare Cu^II–F bond, resulting from dissociation of a BF₄⁻ ion. The F⁻ ligands actively participate in the crystal structure, behaving as acceptors for hydrogen bonding.