Comparative Analysis of the Crystal Structures and Physical Properties of the Complex Group 14 Selenides Sr8Ge4Se17 and Ba8Sn4Se17

During our group's continued exploration of group 14 chalcogenides, we discovered two new compounds, Sr8Ge4Se17 and Ba8Sn4Se17. Both compounds have an 8:4:17 stoichiometric ratio but adopt different centrosymmetric crystal structures. Sr8Ge4Se17 crystallizes in the triclinic P1̅ space group with a = 11.8429(18) Å, b = 12.172(3) Å, c = 13.624(3) Å, α = 114.472(5)0, β = 97.396(5)0, γ = 107.040(5)0, and Z = 2. Ba8Sn4Se17 crystallizes in the monoclinic C2/c space group with a = 47.286(3) Å, b = 12.6294(5) Å, c = 25.7303(15) Å, β = 104.585(5)0, and Z = 16. The unit cell of Ba8Sn4Se17 is approximately eight times larger than the unit cell of Sr8Ge4Se17, which is a consequence of the differently aligned tetrahedra, resulting in a quadrupled a axis, unchanged b axis, and doubled c axis. The lattice parameters and atomic coordinates were finalized via Rietveld refinements on data collected at a high-energy synchrotron beamline. Both compounds are semiconductors with band gaps in the visible region. Sr8Ge4Se17 and Ba8Sn4Se17 have optical band gaps of 1.88 and 1.93 eV, respectively. Both compounds have remarkably low thermal conductivities owing to their low symmetries and large unit cells. The minimum experimental thermal conductivity values of Sr8Ge4Se17 and Ba8Sn4Se17 are 0.45 W m-1 K-1 at 321 K and 0.31 W m-1 K-1 at 324 K, respectively.

Crystal structure, phase width, and physical properties of the barium tetrel selenides Ba6Si2-xGexSe12 (x = 0, 0.5, 1, and 1.5) with ultralow thermal conductivity

The new compound Ba6Si2Se12 was synthesized, and the crystal structure and physical properties are reported here. Ba6Si2Se12 adopts a new structure type in the triclinic P1̄ space group with the lattice parameters a = 9.1822(7) Å, b = 12.2633(14) Å, c = 12.3636(18) Å, α = 109.277(3)°, β = 104.734(2)°, and γ = 100.4067(16)°. Notably, the structure features disordered Se22- dumbbells that have also been observed in the germanium selenide with the analogous stoichiometry (Ba6Ge2Se12). Density functional theory calculations revealed that Ba6Si2Se12 is a semiconductor with a calculated band gap of 1.74 eV. UV/vis/NIR absorption spectra indicated that the experimental band gap of Ba6Si2Se12 is 1.89 eV. While exploring this compound's phase width, it was discovered that up to 75% of the Si could be substituted with Ge while retaining the structure type. Rietveld refinements were performed on the phase-pure samples of Ba6Si2-xGexSe12 (x = 0, 0.5, 1, and 1.5) using data collected at the Canadian Light Source's High Energy Wiggler Beamline. The cell parameters, Si/Ge occupancies, and disordered Se22- occupancies were studied. Raman spectra displayed the expected Si-Se and Ge-Se stretching modes from 215 cm-1 to 280 cm-1. The samples were also hot-pressed into pellets to determine their thermal conductivity values ranging from 0.5 to 0.4 W m-1 K-1 for the x = 0, 0.5, and 1.5 samples. The x = 1 sample stood out with a remarkably low thermal conductivity of 0.3 W m-1 K-1, consistent from room temperature up to 573 K.

A New Sodium Thioborate Fast Ion Conductor: Na 3 B 5 S 9

We report a new sodium fast-ion conductor, Na3B5S9, that exhibits a high Na ion total conductivity of 0.80 mS∙cm-1 (sintered pellet; cold-pressed pellet = 0.21 mS∙cm-1). The structure consists of corner-sharing B10S20 supertetrahedral clusters, which create a framework that supports 3D Na ion diffusion channels. The Na ions are well-distributed in the channels and form a disordered sublattice spanning five Na crystallographic sites. The combination of structural elucidation via single crystal X-ray diffraction and powder synchrotron X-ray diffraction at variable temperatures, solid-state nuclear magnetic resonance spectra and ab initio molecular dynamics simulations reveal high Na-ion mobility (predicted conductivity: 0.96 mS∙cm-1) and the nature of the 3D diffusion pathways. Notably, the Na ion sublattice orders at low temperatures, resulting in isolated Na polyhedra and thus much lower ionic conductivity. This highlights the importance of a disordered Na ion sublattice - and existence of well-connected Na ion migration pathways formed via face-sharing polyhedra - in dictating Na ion diffusion.

Ba6Ge2Se12 and Ba7Ge2Se17: Two Centrosymmetric Barium Seleno-Germanates with Polyatomic Anion Disorder

Herein, the crystal structures and physical properties of two previously unreported barium seleno-germanates, Ba₆Ge₂Se₁₂ and Ba₇Ge₂Se₁₇, are presented. Ba₆Ge₂Se₁₂ adopts the P2₁/c space group with a = 10.0903(2) Å, b = 9.3640(2) Å, c = 25.7643(5) Å, and β = 90.303(1)°, whereas Ba₇Ge₂Se₁₇ crystallizes in the Pnma space group with a = 12.652(1) Å, b = 20.069(2) Å, c = 12.3067(9) Å. Both structures feature polyatomic anion disorder: [Se₂]^2- in the case of Ba₆Ge₂Se₁₂ and [GeSe₅]^4- in the case of Ba₇Ge₂Se₁₇. The anion disorder is verified by comparing pair distribution functions of ordered and disordered models of the structures. These anions are split unevenly across two possible sets of atomic coordinates. The optical band gaps obtained from the powdered samples are found to be 1.75 and 1.51 eV for Ba₆Ge₂Se₁₂ and Ba₇Ge₂Se₁₇, respectively. Differential scanning calorimetry experiments indicate that the compounds are stable under the exclusion of air up to at least 673 K. The thermal diffusivity measurements revealed thermal conductivities reaching values as low as 0.33 W m^-1 K^-1 in both compounds at 573 K.

Structure of the Solid-State Electrolyte Li3+2xP1-xAlxS4: Lithium-Ion Transport Properties in Crystalline vs Glassy Phases

The search for new solid electrolyte materials and an understanding of fast-ion conductivity are crucial for the development of safe and high-power all-solid-state battery technology. Herein, we present the synthesis, structure, and properties of a crystalline lithium-ion conductor, Li_3.3Al_0.15P_0.85S₄ (i.e., Li_9.9Al_0.45P_2.55S₁₂), found in the compositional range Li_3+2xP_1-xAl_xS₄ (x = 0.15, 0.20, and 0.33). ³¹P magic-angle spinning nuclear magnetic resonance (MAS-NMR) aided in identifying the successful introduction of Al into the lattice. At high values of x (>0.15), crystalline Li₅AlS₄ and a glassy amorphous component exsolve to yield a multiphase mixture. The crystal structure of Li_3.3Al_0.15P_0.85S₄ was elucidated by single-crystal X-ray diffraction and powder neutron diffraction, demonstrating that it belongs to the thio-LISICON family with the Pnma space group, a = 12.9572(13) Å, b = 8.0861(8) Å, c = 6.1466(6) Å, and V = 644.00(11) ų. The Li⁺-ion conductivity and diffusivity in this bulk material (which contains about 10 wt % of an amorphous phase, as prepared) were studied by electrochemical impedance spectroscopy and ⁷Li pulsed-field gradient nuclear magnetic resonance spectroscopy (PFG-NMR). The total ionic conductivity of Li_3.3Al_0.15P_0.85S₄ is 0.22(2) mS·cm^-1 at room temperature with an activation energy of 0.30(1) eV. A two-component analysis method based on the Kärger equations was developed to analyze the diffusive exchange between the bulk and amorphous phases of Li_3.3Al_0.15P_0.85S₄ detected via the PFG-NMR signal attenuation curves. This approach was employed to quantitatively compare different sample morphologies (glass powder, crystalline powder, and crystalline pellets of Li_3.3Al_0.15P_0.85S₄) and assess the influence of the macroscopic state on microscopic ion transport, as supported by NMR relaxation measurements.

Thermoelectric Properties of Hot-Pressed Ba3Cu14-δTe12

The aim of this study was to investigate the thermoelectric properties of hot-pressed Ba₃Cu_14-δTe₁₂ as well as its stability with regards to Cu ion movement. For the latter, two single crystals were picked from pellets after they were measured up to 573 and 673 K, which showed no significant changes in the occupancies of any of the Cu sites. All investigated Ba₃Cu_14-δTe₁₂ materials displayed low thermal conductivity values (<1 W m^-1 K^-1) and appropriate electrical conductivity values (300-600 Ω^-1 cm^-1). However, the thermopower values were comparably low (<+65 μV K^-1), resulting in uncompetitive zT values, with the highest being achieved for Ba₃Cu_13.175Te₁₂, namely zT = 0.12 at 570 K. In an attempt to decrease the thermal conductivity, and thereby enhance the figure of merit, a brief alloying study with Ag was undertaken. The incorporation of Ag, however, did not produce any significant improvements.

Fast Ion-Conducting Thioboracite with a Perovskite Topology and Argyrodite-like Lithium Substructure

We report a new fast ion-conducting lithium thioborate halide, Li₆B₇S₁₃I, that crystallizes in either a cubic or tetragonal thioboracite structure, which is unprecedented in boron-sulfur chemistry. The cubic phase exhibits a perovskite topology and an argyrodite-like lithium substructure that leads to superionic conduction with a theoretical Li-ion conductivity of 5.2 mS cm^-1 calculated from ab initio molecular dynamics (AIMD). Combined single-crystal X-ray diffraction, neutron powder diffraction, and AIMD simulations elucidate the Li⁺-ion conduction pathways through 3D intra- and intercage connections and Li-ion site disorder, which are all essential for high lithium mobility. Furthermore, we demonstrate that Li⁺ ordering in the tetragonal polymorph impedes lithium-ion conduction, thus highlighting the importance of the lithium substructure and lattice symmetry in dictating transport properties.

Effect of Pb Substitution in Sr2-xPbxGeSe4 on Crystal Structures and Nonlinear Optical Properties Predicted by DFT Calculations

We investigated the Sr_2-xPb_xGeSe₄ series from 0 ≤ x ≤ 2 to study the impact of Pb on structure and properties. While the noncentrosymmetric (NCS) compounds γ-Sr₂GeSe₄ and α-Pb₂GeSe₄ have already been reported previously, the substitution variants Sr_1.31Pb_0.69GeSe₄ (space group Ama2, a = 10.31220(1) Å, b = 10.39320(1) Å, c = 7.42140(1) Å) and Sr_0.19Pb_1.81GeSe₄ (I4̅3d, a = 14.6177(3) Å) are introduced here for the first time. The experimentally determined optical band gaps decrease as predicted with increasing Pb content from γ-Sr₂GeSe₄ to Sr_1.31Pb_0.69GeSe₄, Sr_0.25Pb_1.75GeSe₄, and α-Pb₂GeSe₄ from 2.00, to 1.65, 1.45 and 1.42 eV, respectively. The nonlinear optical (NLO) properties of the orthorhombic compounds γ-Sr₂GeSe₄ and Sr_1.3Pb_0.7GeSe₄ (approximated with the supercell "Sr₃PbGe₂Se₈") were studied both theoretically, using first-principle calculations, and experimentally. The calculations found the effective nonlinear susceptibility, d_eff, of γ-Sr₂GeSe₄ and "Sr₃PbGe₂Se₈" at the static limit to be 10.8 and 8.8 pm V^-1, respectively. The experimental d_eff values of γ-Sr₂GeSe₄, Sr_1.31Pb_0.69GeSe₄, Sr_0.25Pb_1.75GeSe₄, and α-Pb₂GeSe₄ were 2.6, 2.3, 0.68, and 0.79 pm V^-1, respectively.

New Family of Argyrodite Thioantimonate Lithium Superionic Conductors

We report on a new family of argyrodite lithium superionic conductors, as solid solutions Li_6+xM_xSb_1-xS₅I (M = Si, Ge, Sn), that exhibit superionic conductivity. These represent the first antimony argyrodites to date. Exploration of the series using a combination of single crystal X-ray and synchrotron/neutron powder diffraction, combined with impedance spectroscopy, reveals that an optimal degree of substitution (x), and substituent induces slight S^2-/I^- anion site disorder-but more importantly drives Li⁺ cation site disorder. The additional, delocalized Li-ion density is located in new high energy lattice sites that provide intermediate interstitial positions (local minima) for Li⁺ diffusion and activate concerted ion migration, leading to a low activation energy of 0.25 eV. Excellent room temperature ionic conductivity of 14.8 mS·cm^-1 is exhibited for cold-pressed pellets-up to 24 mS·cm^-1 for sintered pellets-among the highest values reported to date. This enables all-solid-state battery prototypes that exhibit promising properties. Furthermore, even at -78 °C, suitable bulk ionic conductivity of the electrolyte is retained (0.25 mS·cm^-1). Selected thioantimonate iodides demonstrate good compatibility with Li metal, sustaining over 1000 h of Li stripping/plating at current densities up to 0.6 mA·cm^-2. The significantly enhanced Li ion conduction and lowered activation energy barrier with increasing site disorder reveals an important strategy toward the development of superionic conductors.

Aromatic Embrace Motifs for Bulk Supramolecular Polymers

Frequently encountered in crystalline materials, aromatic embraces (AEs) are formed when arylated molecules interact through multiple concerted aromatic interactions. AEs are a robust motif that is suitable for the preparation of amorphous bulk supramolecular polymers (BSPs). Crystal engineering revealed that the polymorphic compound (PPh₃ )(Cp)Fe(CO){CO(CH₂ )₅ CH₃ } (Cp=cyclopentadienyl), known as FpC₆ , assembled into various chain structures through several AE motifs. Upon melting, FpC₆ always adopted the same AE motif, which extended into the corresponding embracing "ladder" chains. The resultant BSP displayed typical polymer behaviour, including the presence of a glass transition and viscoelasticity, which allowed the effect of thermal history on the polymerisation behaviour to be explored. The ladder chains formed by the AE remain assembled at temperatures of up to 130 °C and were able to effectively suppress crystallisation during cooling. The ability of the AE to form chains at high temperatures and suppress crystallisation is a new opportunity to advance the field of BSPs and supramolecular chemistry.

Characterization of 3-[(Carboxymethyl)thio]picolinic Acid: A Novel Inhibitor of Phosphoenolpyruvate Carboxykinase

Phosphoenolpyruvate carboxykinase (PEPCK) has traditionally been characterized for its role in the first committed step of gluconeogenesis. The current understanding of PEPCK's metabolic role has recently expanded to include it serving as a general mediator of tricarboxylic acid cycle flux. Selective inhibition of PEPCK in vivo and in vitro has been achieved with 3-mercaptopicolinic acid (MPA) (K_i ∼ 8 μM), whose mechanism of inhibition has been elucidated only recently. On the basis of crystallographic and mechanistic data of various inhibitors of PEPCK, MPA was used as the initial chemical scaffold to create a potentially more selective inhibitor, 3-[(carboxymethyl)thio]picolinic acid (CMP), which has been characterized both structurally and kinetically here. These data demonstrate that CMP acts as a competitive inhibitor at the OAA/PEP binding site, with its picolinic acid moiety coordinating directly with the M1 metal in the active site (K_i ∼ 29-55 μM). The extended carboxy tail occupies a secondary binding cleft that was previously shown could be occupied by sulfoacetate (K_i ∼ 82 μM) and for the first time demonstrates the simultaneous occupation of both OAA/PEP subsites by a single molecular structure. By occupying both the OAA/PEP binding subsites simultaneously, CMP and similar molecules can potentially be used as a starting point for the creation of additional selective inhibitors of PEPCK.

BaCuSiTe3: A Noncentrosymmetric Semiconductor with CuTe4 Tetrahedra and Ethane-like Si2Te6 Units

BaCuSiTe₃ was prepared from the elements in a solid-state reaction at 973 K, followed by slow cooling to room temperature. This telluride adopts a new, hitherto unknown structure type, crystallizing in the noncentrosymmetric space group Pc with a = 7.5824(1) Å, b = 8.8440(1) Å, c = 13.1289(2) Å, β = 122.022(1)°, and V = 746.45(2) ų (Z = 4). The structure consists of a complex network of two-dimensionally connected CuTe₄ tetrahedra and ethane-like Si₂Te₆ units with a Si-Si bond. This semiconducting material has an optical band gap of 1.65 eV and a low thermal conductivity of 0.50 W m^-1 K^-1 at 300 K. Calculations of its optical properties revealed a moderate birefringence of 0.23 and a second-order harmonic generation response of d_eff = 3.4 pm V^-1 in the static limit.

Two-Dimensional Metal-Organic Framework Nanosheets as a Dual Ratiometric and Turn-off Luminescent Probe

Current research on metal-organic framework (MOF) luminescent sensing probes focuses on the design of three-dimensional bulk-sized MOFs that in return limits their up-close interactions with targeted guest molecules. In this work, we report a two-dimensional (2D) copper-based metal-organic framework, namely, AUBM-6, synthesized via solvothermal method from isonicotinic acid linker and copper(II) ion. The resulting 2D-layered MOF crystals were highly fluorescent in their exfoliated form and, therefore, explored for detecting several solvents, where a ratiometric selectivity was shown toward acetone. Metal ion sensing was also performed, by which fluorescent detection was observed to have the highest turn-off quenching efficiency toward Pd²⁺.

Effect of mixed occupancies on the thermoelectric properties of BaCu6-xSe1-yTe6+y polychalcogenides

The title materials have been reported earlier to be p-type thermoelectrics when x = 0.1 and y = 0. Here, we studied the properties after varying the Cu and the Se/Te concentrations. At first, materials with the same nominal Cu concentration, 5.9 Cu per formula unit, and different Se/Te ratios were prepared. The different thermoelectric properties indicated that the Se/Te ratio strongly affected the Cu deficiency, which is directly responsible for the charge carrier concentration. Single crystal structure data revealed the Cu amount to be less than 5.8 per formula unit when y = 0.4; therefore a sample of nominal composition "BaCu5.74Se0.46Te6.54" was also studied. This sample exhibited an electrical conductivity of 685 Ω-1 cm-1 at room temperature, which is almost three times larger than in case of "BaCu5.9SeTe6", in accord with the lower Cu amount causing a larger hole concentration. The larger mass fluctuation on the Se/Te site resulted in a lower lattice thermal conductivity, but the decreased Seebeck coefficient mitigated a performance increase in form of a higher figure-of-merit. In contrast to other Cu chalcogenides, the data are reproducible under the measurement conditions.

Structural investigation of a new cadmium coordination compound prepared by sonochemical process: Crystal structure, Hirshfeld surface, thermal, TD-DFT and NBO analyses

A new nanostructured cadmium complex containing a tridentate Schiff base ligand was sonochemically synthesized and characterized by XRPD, FT/IR, NMR, and single crystal X-ray crystallography. Structural data showed that cadmium(II) ion is surrounded by three nitrogen atoms of Schiff base ligand and two iodide anions. The crystal packing was contained the intermolecular interactions such as CH⋯O, CH⋯I and π⋯π interactions organizing the self-assembly process. Hirshfeld surfaces and corresponding fingerprint plots have been used for investigation of the nature and proportion of interactions in the crystal packing. FT/IR, NMR and XRD data were in agreement with the X-ray structure and confirm the phase purity of the prepared sample. The molecular structure of the complex was optimized by density functional theory (DFT) calculation at the B3LYP/LANL2DZ level of theory and the results were compared with experimental ones. For more concise study of structure and spectral aspects of the complex, natural bond orbital (NBO) analysis and time-dependent density functional theory (TD-DFT) have been also performed. Thermal stability of the cadmium iodide complex was investigated by thermogravimetric analysis (TGA). Finally, cadmium oxide nanoparticles was prepared by direct calcination of CdLI₂ complex as a new precursor.

A New Material with a Composite Crystal Structure Causing Ultralow Thermal Conductivity and Outstanding Thermoelectric Properties: Tl2Ag12Te7+δ

A new state-of-the-art thermoelectric material, Tl₂Ag₁₂Te_7+δ, which possesses an extremely low thermal conductivity of about 0.25 W m^-1 K^-1 and a high figure-of-merit of up to 1.1 at 525 K, was obtained using a conventional solid-state reaction approach. Its subcell is a variant of the Zr₂Fe₁₂P₇ type, but ultimately its structure was refined as a composite structure of a Tl₂Ag₁₂Te₆ framework and a linear Te atom chain running along the c axis. The super-space group of the framework was determined to be P6₃(00γ) s with a = b = 11.438(1) Å, c = 4.6256(5) Å, and that of the Te chain substructure has the same a and b axes, but c = 3.212(1) Å, space group P6(00γ) s. The modulation leads to the formation of Te₂ and Te₃ fragments in this chain and a refined formula of Tl₂Ag_11.5Te_7.4. The structure consists of a complex network of three-dimensionally connected AgTe₄ tetrahedra forming channels filled with the Tl atoms. The electronic structures of four different models comprising different Te chains, Tl₂Ag₁₂Te₇, Tl₂Ag₁₂Te_7.33, and 2× Tl₂Ag₁₂Te_7.5, were computed using the WIEN2k package. Depending on the Te content within the chain, the models are either semiconducting or metallic. Physical property measurements revealed semiconducting properties, with an ultralow thermal conductivity, and excellent thermoelectric properties at elevated temperatures.

Benzoquinone-Bridged Heterocyclic Zwitterions as Building Blocks for Molecular Semiconductors and Metals

In pursuit of closed-shell building blocks for single-component organic semiconductors and metals, we have prepared benzoquino-bis-1,2,3-thiaselenazole QS, a heterocyclic selenium-based zwitterion with a small gap (λ_max = 729 nm) between its highest occupied and lowest unoccupied molecular orbitals. In the solid state, QS exists in two crystalline phases and one nanocrystalline phase. The structures of the crystalline phases (space groups R3 c and P2₁/ c) have been determined by high-resolution powder X-ray diffraction methods at ambient and elevated pressures (0-15 GPa), and their crystal packing patterns have been compared with that of the related all-sulfur zwitterion benzoquino-bis-1,2,3-dithiazole QT (space group Cmc2₁). Structural differences between the S- and Se-based materials are interpreted in terms of local intermolecular S/Se···N'/O' secondary bonding interactions, the strength of which varies with the nature of the chalcogen (S vs Se). While the perfectly two-dimensional "brick-wall" packing pattern associated with the Cmc2₁ phase of QT is not found for QS, all three phases of QS are nonetheless small band gap semiconductors, with σ_RT ranging from 10^-5 S cm^-1 for the P2₁/ c phase to 10^-3 S cm^-1 for the R3 c phase. The bandwidths of the valence and conduction bands increase with applied pressure, leading to an increase in conductivity and a decrease in thermal activation energy E_act. For the R3 c phase, band gap closure to yield an organic molecular metal with a σ_RT of ∼10² S cm^-1 occurs at 6 GPa. Band gaps estimated from density functional theory band structure calculations on the ambient- and high-pressure crystal structures of QT and QS correlate well with those obtained experimentally.

Thermoelectric properties and thermal stability of layered chalcogenides, TlScQ2, Q = Se, Te

A few thallium based layered chalcogenides of α-NaFeO₂ structure-type are known for their excellent thermoelectric properties and interesting topological insulator nature. TlScQ₂ belongs to this structural category. In the present work, we have studied the electronic structure, electrical and thermal transport properties and thermal stability of the title compounds within the temperature range 2-600 K. Density functional theory (DFT) predicts a metallic nature for TlScTe₂ and a semiconducting nature for TlScSe₂. DFT calculations also show significant lowering of energies of frontier bands upon inclusion of spin-orbit coupling contribution in the calculation. The electronic structure also shows the simultaneous occurrence of holes and electron pockets for the telluride. Experiments reveal that the telluride shows a semi-metallic behaviour whereas the selenide is a semiconductor. The thermoelectric properties for both the materials were also investigated. Both these materials possess very low thermal conductivity which is an attractive feature for thermoelectrics. However, they lack thermal stability and decompose upon warming above room temperature, as evidenced from high temperature powder X-ray diffraction and thermal analysis.

Crystal structure, electronic structure and physical properties of the new quaternary chalcogenides Tl2NdAg3Se4 and Tl2NdAg3Te4

Two new quaternary chalcogenides are presented, which are bestowed with extraordinarily low thermal conductivity.

Spin Frustration in an Organic Radical Ion Salt Based on a Kagome-Coupled Chain Structure

Electro-oxidation of the quinoidal bisdithiazole BT in dichloroethane in the presence of [Bu4N][GaBr4] affords the 1:1 radical ion salt [BT][GaBr4], crystals of which belong to the trigonal space group P3. The packing pattern of the radical cations provides a rare example of an organic kagome basket structure, with S = 1/2 radical ion chains located at the triangular corners of a trihexagonal lattice. Magnetic measurements over a wide temperature range from 30 mK to 300 K suggest strongly frustrated AFM interactions on the scale of J/kb ∼ 30 K, but reveal no anomalies that would be associated with magnetic order. These observations are discussed in terms of the symmetry allowed magnetic interactions within and between the frustrated layers.

Pushing TC to 27.5 K in a heavy atom radical ferromagnet

In the solid state the iodo-substituted bisdiselenazolyl radical 1c orders as a bulk ferromagnet with T_C = 10.5 K. With the application of pressure T_C rises rapidly, reaching a value of 27.5 K at 2.4 GPa.

DFT study and crystal structure analysis of a new nano-structure five coordinated Hg(II) complex involving C-H⋯O, N⋯O and π⋯π interactions in a supra-molecular structure

In this research, template synthesis and crystal structure of a new HgLI₂ complex are presented (L=N(1)-(4-nitrobenzylidene)-N(2)-(2-((E)-(4-nitrobenzylidene)amino)ethyl)ethane-1,2-diamine). The mercury complex crystallizes in the triclinic system with space group of P1¯. The crystal structure of the complex shows a distorted trigonal bipyramidal geometry around the mercury(II) center; including two I and an N atoms of Schiff base ligand in equatorial plane and two iminic N atoms in axial positions. Two five membered mercury containing rings [Hg(-N-C-C-N-)] are found in the structure. Some C-H⋯O, N⋯O and π⋯π intermolecular interactions causes a supra-molecular network in the solid-state. In addition to crystal structure analysis, density functional theory (DFT) study at the B3LYP/LanL2DZ level of theory has been also performed on the structure. Thereafter some theoretical structural and spectral data were compared with experimental results. Furthermore, total energy levels of HOMO and LUMO orbitals, molecular electrostatic potential, Mullikan atomic charges, thermodynamic and polarizability properties of the complex were calculated. Finally the mercury complex was prepared in nano-structure size confirmed by SEM and XRD analyses. The particles size of the titled complex was evaluated under 40 nm based on Sherrer's formula.

The structure, magnetism and EPR spectra of a (μ-thiophenolato)(μ-pyrazolato-N,N') double bridged dicopper(II) complex

A new binuclear copper(ii) complex, namely [Cu2L(pz)(DMSO)], where L = 2,6-bis[(2-phenoxy)iminomethyl]-4-methylthiophenolate(3-) and pz = pyrazolate ligand, has been synthesized by a one-pot synthesis involving copper(ii) acetate monohydrate, the S-protected ligand precursor 2-(N,N-dimethylthiocarbamato)-5-methylisophthalaldehyde di-2'-hydroxy anil, (), and pyrazole, in which a metal-promoted S-deprotection reaction occurs during the formation of the complex. This was characterized by routine physicochemical studies, single crystal X-ray diffraction and electron paramagnetic resonance (EPR) techniques. The structure analysis reveals that there are copper centres in two different environments, a slightly distorted square planar and a distorted square-pyramidal, arranged in binuclear units. The EPR study of these binuclear units performed at 9.4 GHz in the temperature range between 4 and 293 K shows an antiferromagnetic interaction between Cu(II) ions, and allows evaluating g factors gx = 2.068(1), gy = 2.091(1) and gz = 2.165(1), with <g> = 2.108(1), an exchange coupling parameter J0 = -26(1) cm(-1) (defined as ), and a zero field splitting of the ground triplet state described by D = 86(2) × 10(-4) cm(-1) and E = -48(3) × 10(-4) cm(-1). These results are discussed and compared with the existing literature.

Intermolecular Interactions of CpFePPh3(CO)CO(CH2)5CH3: From a Crystalline Solid to a Supramolecular "Iron-Truss" Polymer

PPh₃CpFe(CO)(CO)(CH₂)₅CH₃ (FpC6) spontaneously forms supramolecular polymers in the solid state. The polymers crystallize slowly over a period of one month and can be recovered by melting the crystals at 65 °C. The rheological profile of FpC6 fits the Maxwell model indicating the presence of chain entanglement. Crystal analysis reveals that FpC6 is able to assemble, via cooperative π-π interactions and weak C-H···O hydrogen bonding, into a duplex chain structure with truss arrangement of iron atoms. Powder X-ray diffraction (PXRD) of the polymers shows a double-peak pattern, characteristic for duplex ladder polymers. FTIR/ATR analysis further supports that carbonyl groups are involved in C-H···O hydrogen bonding responsible for the self-assembly. This discovery opens up new design motifs for organometallic supramolecular polymers.

N-Benzyl-2-chloro-quinazolin-4-amine

The asymmetric unit of the title compound, C15H12ClN3, contains two independent mol-ecules. The quinazoline ring system in each is essentially planar, with maximum deviations of 0.025 (16) and 0.0171 (16) Å. The dihedral angles between quinazoline ring systems and the phenyl rings are 88.25 (8) and 85.28 (16)° in the two independent mol-ecules. In the crystal, alternating independent mol-ecules are linked by N-H⋯N hydrogen bonds, forming chains along [001].

A common synthetic route to homochiral tetracycles related to pillaromycinone and premithramycinone

Homochiral AB segments for (+)- and (–)-pillaromycinone were prepared in 11 steps from 2-acetylfuran. The synthesis featured an intramolecular Diels–Alder reaction of a 2,5-disubstituted furan and a hydroxyl-directed homogeneous hydrogenation of the tetrasubstituted alkene double bond of two enones. The CD segment was attached by a modified Staunton–Weinreb annulation to produce the desired homochiral tetracycle 21c related to (+)-pillaromycinone. An unusual acetonide migration enabled the synthesis of a tetracyclic model for premithramycinone.