Synthesis of tetra-silylated tetrathiafulvalene derivatives TTF(SiR2H)4 (R = Me,Ph): Novel assembling ligands for the construction of bimetallic transition metal complexes

The HR₂Si-functionalized tetrathiafulvalene (TTF) ligand TTF(SiR₂H)₄ (R = Me 2a; R = Ph 2b) have been synthesized and the molecular structure of 2a determined. The reactivity of the four Si–H bonds for oxidative addition reactions has been exploited. Thus, the bimetallic platinum–silicon complex [(PPh₃)₂Pt{(Me₂Si)₂TTF(SiMe₂)₂}Pt(PPh₃)₂] 3 incorporating TTF(SiMe₂H)₄ as bridging unit has been assembled by oxidative addition across [Pt(PPh₃)₂(CH₂CH₂)]. Electrochemical investigations by means of cyclic voltammetry reveals, for the complex 3, a strong cathodic shift of the two redox processes of the TTF core compared with those of 2a.     

Crystalline patterns and band structure dimensionality in a series of conducting hybrids associating amide-functionalized EDT-TTF π-donors with the isosteric octahedral anions [FeNO(CN)5]2− and [M(CN)6]3− (M = Co,Fe)

Four new radical cation salts based on the amide functionalized EDT-TTF organic donors EDT-TTF-CONH₂ (D1) and EDT-TTF-(CONH₂)₂ (D2), α′-(D1)₄[FeNO(CN)₅] (1), α′-(D1)₄[Co(CN)₆] (2), β-(D1)₆[Fe(CN)₆] (3) and (D2)₄[FeNO(CN)₅]NB (4), have been synthesized and characterized by X-ray single crystal diffraction experiments, band structure calculations and electrical resistivity measurements. Functionalized organic donors are remarkable for the ability to form cation⋯cation and cation⋯anion type hydrogen bonds which can effectively direct the crystal architecture of molecular conductors. The structural analysis reveals a well-developed hydrogen bond network in the crystals investigated. (D1)₂-dimers or (D2)_n-extended zigzag chains of donors connected through functional groups are found to be stable structural motifs in 1–4. Remarkably, salts 1 and 2 are isostructural despite the presence of anions of different charge (−2 and −3, respectively) and the inherent difference in the degree of charge transfer has a clear effect on the transport properties: σ_RT(2)/σ_RT(1) = 300. Salt 3 differs from 1 and 2 both in the stoichiometry and packing of the conducting organic layer. Crystals of 4 exhibit a superstructure with the incommensurate vector q = ±(0.5, 0.3, 0.2).     

Synthesis of CETBz-TTF and CESBz-TTF: Preparation, structural and physical properties of their radical salts with paramagnetic Cu(II) complex anions

CETBz-TTF (4,5-bis(cyanoethylthio)benzo-tetrathiafulvalene) and CESBz-TTF (4,5-bis(cyanoethylseleno)benzo-tetrathiafulvalene) 5 have been synthesized from cyano precursor via a cross-coupling reaction. Radical salts with paramagnetic Cu(II) complex anions, such as (CETBz-TTF)₂CuCl₄ 6 and (CESBz-TTF)₂CuCl₄ 7 have been prepared. X-ray crystal structure and physical properties of these new compounds are presented.     

Multi-component molecular conductors with supramolecular assembly based on ET radical cation salts with (NO3)− anion

Synthesis, structure and conducting properties of two new multi-component radical cation ET salts with the (NO₃)⁻ counterion: (ET)₂(NO₃)·C₂H₄(OH)₂ (I) and (ET)₂(NO₃)·0.5[C₂H₄(OH)₂]·H₂O (II) are described. Both salts have layered structures with the distinguishing feature of hydrogen bonds being present between the radical cation layers and anion sheets. It was found that introduction of glycol molecules to compositions of I and II significantly affects the structure of their cation and anion layers and, as a result, their conducting properties. I is a semiconductor, while II demonstrates metallic conductivity down to 4.2 K.     

Temperature anomalies of deformation behavior and dislocation structure of Ti3Al: A review

Experimental data on the temperature anomalies of deformation characteristics and dislocation structure of Ti₃Al oriented for pyramidal slip have been reviewed. The results of the investigations that are performed by the method of computer simulation with the use of N-particle potentials of interatomic interaction have been reported. The subject of the studies was the core structure of 2c + a superdislocations in pyramid planes in glissile configurations and configurations of dislocation barriers. A dislocation model of thermally activated formation and destruction of dislocation barriers that are responsible for the anomaly of the deformation behavior of Ti₃Al has been discussed; the model makes it possible to account for the observed experimental data.     

Copper(I) coordination ability of the outer S-position isomer of EDT-DMT-TTF (D1): crystal structure of (D1)2Cu2Br4,2CH2Cl2; structural correlation with the (D1)2Cu2Br6 copper(II) salt

The (D1)₂Cu₂Br₄,2CH₂Cl₂ (1) and (D1)₂Cu₂Br₆ (2) radical cation salts, where D1 is the outer S-position isomer of ethylenedithiodimethylthiotetrathiafulvalene (EDT-DMT-TTF), have been synthesized and their X-ray crystal structures have been solved. The molecular structure of 1 is built up from (D1–Cu₂Br₄–D1) metal complexes. Each copper(I) atom is coordinated to a sulfur atom of the D1 disulfide bridge through a σ-type dative bond. Consequently, Cu₂Br₄ part is located between two organic molecules which are approximately plane and parallel to each other. In compound 2, (Cu₂Br₆)²⁻ anions, in which copper atoms are at the +2 oxidation state, also lie between two oxidized donors. In both resulting structures, the D1–Cu₂Br_x–D1 parts (x=4 for 1, x=6 for 2) are stacking in order to form columns containing dimerized (D1⁺)₂ units.     

2D double-layered metal–radical complexes: Crystal structures and magnetic properties

Two new complexes [Mn(NIT4Py)(2,4-PDA)(H₂O)₂] (1) and [Co(NIT4Py)(2,4-PDA)(H₂O)₂] (2) (where NIT4Py stands for 2-(4′-pyridinyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, 2,4-PDA stands for pyridine-2,4-dicarboxylate) have been synthesized and characterized. The single-crystal X-ray diffraction demonstrates that complex 1 present dimeric structure with two 2,4-PDA anions function as bridging ligands, connecting two Mn(II) centers. The dimeric units form an infinite 2D double-layered network via hydrogen bonds. Complex 2 consists of infinite 1D chain, in which each 2,4-PDA anion bridges two adjacent Co(II) ions in monodentate–bidentate mode. These 1D chains are further connected together by hydrogen bonds, generating a 2D double-layered structure, too. The variable temperature magnetic susceptibility measurements reveal that the magnetic couplings between Mn(II) and NIT4Py, Co(II) and NIT4Py are weak ferromagnetic and antiferromagnetic interactions for complexes 1 and 2, respectively.     

Syntheses,structures, and luminescent properties of cadmium (II) complexes: 3D supramolecular [Cd(phen)(NO3)(NO2)(H2O)]n and Cd(phen)2(NO3)(NO2) constructed by π–π stacking interactions

Two novel complexes [Cd(phen)(NO₃)(NO₂)(H₂O)]_n (1) and Cd(phen)₂(NO₃)(NO₂) (2) (phen = 1,10-phenanthroline) have been synthesized by the reductive reaction of metal source Cd(NO₃)₂·4H₂O with phen and benzidine in the mixed solution of DMF, ethanol and water. Crystal structures of complexes 1 and 2 were determined by single-crystal X-ray diffraction. Complex 1 is a one-dimensional (1D) zig-zag infinite chain in which (phen)Cd^(II) units were bridged by two O atoms of NO₂⁻. The three-dimensional (3D) supramolecular structure of 1 is constructed through hydrogen-bond and aromatic π–π stacking interactions between adjacent metal–organic polymeric coordination chains. Complex 2 is a mononuclear structure, and self-assembled through π–π stacking interactions to form a three-dimensional (3D) supramolecular structure. The complex 1 exhibits luminescent property in the near-UV at room temperature in solutions of DMSO and DMF with the emission energy following the order DMF < DMSO, which might be ascribed to the presence of a highly polarized ground state. Complexes 1 and 2 have blue-purple luminescence at room temperature in the solid state. The blue-purple luminescence of the complexes is due to π* → π transition of phen.     

Synthesis and properties of Mo5Si3 single crystals

The ultra-high temperature structural intermetallic Mo₅Si₃ has been studied for alloy processing, physical properties, and mechanical behavior. High purity single crystals of Mo₅Si₃ have been synthesized by both optical floating zone and Czochralski methods. Structural, thermal, and elastic properties of Mo₅Si₃ single crystals were measured by X-ray powder diffraction, thermal mechanical analysis, and resonant ultrasound spectroscopy, respectively. Results show that the thermal expansion of Mo₅Si₃, a tetragonal structure with I4/mcm symmetry, is strongly anisotropic along the a and c directions with α_c/α_a=2.2. Single crystal elastic moduli of Mo₅Si₃ indicate that it has less elastic anisotropy and lower shear modulus than most transition metal disilicides. The impacts of these physical properties on alloy processing and mechanical behavior are discussed. Room temperature Vickers indentation tests on the (100) and (001) planes have been performed for different orientations of the indenter diagonal and the corresponding hardness, fracture toughness, and deformation behavior have been obtained as a function of the crystallography. Finally, the physical properties and mechanical behavior of Mo₅Si₃ are compared with those of other high temperature structural silicides, e.g. MoSi₂.     

Planar defects and dislocations in transition-metal disilicides

The structures of transition-metal disilicides are constituted of different stacking of identical atomic planes at four different positions A, B, C, D: AB in C11_b structure of e.g. MoSi₂, ABC in C40 structure of e.g. VSi₂ and ABDC in C54 structure of e.g. TiSi₂ disilicides. In comparison with the FCC lattice with the ABC atomic plane stacking along the <111> directions, the occurrence of the fourth position, D, essentially alters the properties of defects and consequently the mechanical properties. The effect of generalized planar defects and their impacts on the dislocation core structures are discussed. In particular, we examine stacking faults and related partial dislocations on the basal planes in different types of disilicides as well as the related twin boundaries and dissociated dislocations. Our analysis of the stacking-fault-like defects is based on the calculations of γ-surfaces using ab initio methods. Predictions of possible metastable defects in all types of disilicides are reported.     

A phosphorescent hexa-peri-hexabenzocoronene platinum complex and its time-resolved spectroscopy

Photoluminescence properties of photoactive HBCC_8,2 and HBCPt₂ have been studied. The phenylene-ethynyl-Pt moieties were incorporated onto the bromo functions of HBCBr₂ 1 via double oxidative addition of Pt(PPh₃)₄ to 1 followed by CuI-catalyzed dehydrohalogenation reaction of compound 2 and phenylacetylene to give the desired molecule HBC-Pt₂. Introduction of platinum-phenylacetylene to the hexa-peri-hexabenzocoronenes (HBC) core enhanced the spin–orbit coupling and decreased the phosphorescence lifetime of the triplet state by three orders of magnitude. Photoluminescence measurements revealed unique phosphorescence emission at room temperature and 77 K. On the other hand, symmetric HBC-C_8,2, bearing no platinum, revealed different delayed emissions depending on the temperature measurement. At room temperature, delayed fluorescence appeared while at 77 K, only phosphorescence could be observed. The triplet energy level has been tuned between 2.3 and 1.7 eV by varying the HBC core substituents. In consequence, combination of both the heavy-atom effect and the increased intersystem crossing in the novel double platinum-substituted HBC lead to the exclusive emission of phosphorescence without any residues of fluorescence in the prompt and delayed emission spectra.     

The first BDH-TTP radical cation salts with mercuric counterions, κ-(BDH-TTP)4[Hg(SCN)4]·C6H5NO2 and α′-(BDH-TTP)6[Hg(SCN)3][Hg(SCN)4]

Two new radical cation salts of the non-TTF containing donor BDH-TTP with the thiocyanatomercurate anions were synthesized. The κ-(BDH-TTP)₄[Hg(SCN)₄]·C₆H₅NO₂ (1) and α′-(BDH-TTP)₆[Hg(SCN)₃][Hg(SCN)₄] (2) salts were characterized by single crystal X-ray diffraction, electrical resistance measurements and electronic band structure calculations. Both salts have a layered structure in which the BDH-TTP layers of κ- or α′-type alternate with anionic sheets. The anionic layers of 1 contain the counterion [Hg(SCN)₄]²⁻ and the nitrobenzene molecule which are statistically disordered. Salt 2 contains two different layers (although both of the α′-type) of the organic donors, a somewhat unusual fact in organic conductors. The anion layers of 2 consist of polymeric chains built up from a combination of the two different anions, [Hg(SCN)₃]¹⁻ and [Hg(SCN)₄]²⁻. Salt 1 shows a metallic behavior down to helium temperatures whereas salt 2 exhibits two-phase transitions in the temperature range 295–8 K.     

Synthesis, crystal and band structures, and optical properties of a new framework mercury pnictides: [Hg4As2](InBr3.5As0.5) with tridymite topology

A new framework compound, [Hg₄As₂](InBr_3.5As_0.5) (1), has been prepared by the solid-state reaction of Hg₂Br₂ with elemental In and As at 450 °C. Compound 1 crystallizes in the space group P₆₃/mmc of the Hexagonal system with two formula units in a cell: a = b = 7.7408(6) Å, c = 12.5350(19) Å, V = 650.47(12) Å³. The crystal structure of 1 features a novel 3D framework, [Hg₄As₂]²⁺ with tridymite topology. The optical properties were investigated in terms of the diffuse reflectance and infrared spectra. The electronic band structure along with density of states (DOS) calculated by DFT method indicates that the present compound is semiconductor, and the optical absorption is mainly originated from the charge transitions from Br-4p and As-4p states to Hg-6s and In-5p states.     

Symmetry analysis of magnetic structures possible in TbNi2Si2-TbMn2Si2 solid solutions

TbNi₂Si₂-TbMn₂Si₂ solid solutions have been studied by neutron diffraction to reveal magnetic structures with wave vectors {k ₈} = μ(b ₁–b ₂) + b ₃/2 = 2π [(1–2μ)/2, (1 + 2μ)/2, 0]/a, {k ₁₃} = b ₃/2 = 2π(1/2, 1/2, 0)/a, and {k ₁₄} = 0. The method of calculation is described and the results of calculations are given for the basis functions of irreducible representations of the space group D _4h ¹⁷ (14/mmm) that are used for the most rational search for a real model of the magnetic structure of these solid solutions. The compositions of the magnetic representations for each of the above-mentioned wave vectors and the possible variants of the mutual orientation of atomic magnetic moments in the crystallographic positions in which the magnetically active atoms (Tb, Ni, Mn) are located have been determined.     

Synthesis,X-ray structure and luminescent properties of a new 1D terbium(III) coordination polymer based on 2,4-dichlorophenoxyacetate and 4,4′-bipyridine

A new 1D terbium coordination polymer, {[Tb(2,4-dcpa)₃(H₂O)₂]·(4,4′-bpy)_1.5(H₂O)₂}_n (1) [2,4,-dcpa = 2,4-dichlorophenoxyacetate, 4,4′-bpy = 4,4′-bipyridine], was prepared by hydrothermal synthesis and characterized by IR spectroscopy, elemental analysis, thermogravimetric analysis (TGA) and single-crystal X-ray diffraction. Complex 1 exhibits an infinite chain structure with a {Tb₂(2,4-dcpa)₆(H₂O)₄} dimeric repeat unit. Each Tb³⁺ ion is nine-coordinated to two water molecules, one monodentate carboxylate group and four bridging carboxylate groups in which the carboxylate groups are bonded to the terbium ion in one modes: the chelating–bridging tridentate. Three-dimensional fluorescence spectra of 1 were detected at room temperature under the excitation and the emission wavelengths in the range of 420–750 nm with the interval of 5 nm. The lifetime of 1 in solid-state at room temperature up to 1.132 ms. On the other hand, poor luminescence efficiency has been noted for the Tb³⁺-2,4-dcpa complex.     

Synthesis and characterization of light-emitting materials composed of carbazole,pyrene and fluorene

A series of ethynyl-linked π-conjugated light-emitting molecules with good photoluminescence properties were designed and synthesized through Pd/Cu-catalyzed Sonogashira coupling reaction. The main structure comprised of different fluorophors (pyrene, carbazole, and fluorene), which were linked with triple bonds in order to be screened for high emission efficiency. Optical properties of these synthesized compounds (I_a–I_f) were examined in solutions, thin films and solid states, respectively. All of them showed relative high quantum yields both in solutions (Φ_s: 0.70–0.83) and in films (Φ_f: 0.17–0.34). Light-emitting diode using I_e as an emissive layer was fabricated in the ITO/poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate) (PEDOT:PSS)/I_e/2, 2′, 2″-(1, 3, 5)-benzene-triyl)tris[1-phenyl-1H-benzimidazole] (TPBI)/Al configuration. The maximum emission wavelength of the device was 496 nm. The maximum luminance and electroluminescence efficiency was 1000 cd/m² and 0.41%, respectively.     

Synthesis,structure and luminescent properties of neodymium(III) coordination polymers with 2,3-pyrazinedicarboxylic acid

The coordination polymer [Nd₂(pzdc)₃(H₂O)]_n·nH₂O (complex I) with three-dimensional framework has been prepared by hydrothermal synthesis of 2,3-pyrazinedicarboxylic acid (pzdc) and neodymium nitrate and characterized by elemental analyses, IR spectroscopy, thermal analyses and single crystal X-ray diffraction. The complex crystallizes in monoclinic system, space group P2(1)/c. Every Nd(III) atom in the coordination polymer is nine-coordinated with different coordination environments. The pzdc ligands coordinate to the central Nd(III) atoms in bridging tetradentate, hexadentate, or heptadentate modes. The thermal decomposition of the complex has been predicted with the help of thermal analyses (TG, DTG and DTA). Complex I exhibits luminescent emissions bands in the solid state at room temperature. The isomorphous complex [Nd₄(pzdc)₆(H₂O)₂]_n·3nH₂O (complex II) has also been prepared by hydrothermal reaction under different conditions. Luminescent emission of complex I display selectivity for some heavy metal ions.     

Magnetic structure of the Mn5Si3-type Er5Si3 compound

Neutron diffraction study has been performed on the Er₅Si₃ compound (hexagonal Mn₅Si₃-type, hP16, P6₃/mcm) to understand its magnetic structure. The temperature dependent neutron diffraction results prove that this compound shows a complex antiferromagnetic ordering with sine modulated magnetic moments collinear to the c axis, presenting three subsequent changes in magnetization at ～29 K, 13 K and 10 K on cooling. The high-temperature magnetic component of Er₅Si₃ (C_3v magnetic point group, P31m magnetic space group, K₁ = [0, 0, ±0.277(2)]) exists from 29 K to 10 K, whereas low-temperature magnetic component (symmetry C_1v magnetic point group, Pm magnetic space group, K₂ = [0, ±1/4, 0]) exists from 13 K down to 1.5 K. The low-temperature and high-temperature magnetic components coexist between 13 K and 10 K.     

Theoretical studies on electronic and electron blocking properties of iridium complexes with phenylpyrazolato ligands

The tris(1-phenylpyrazolato,N,C2′)iridium(III) Ir(ppz)₃, (fac-Ir(ppz)₃, 1; mer-Ir(ppz)₃, 2) and iridium(III)bis(1-phenylpyrazolato,N,C2′) (2,2,6,6-tetramethyl-3,5-heptane-dionato-O,O) ppz₂Ir(dpm) (C-cis,N-trans-ppz₂Ir(dpm), 3; C-cis,N-cis-ppz₂Ir(dpm), 4) have been investigated theoretically to explore their electronic structures, spectroscopic and electron blocking properties. A detailed comparison of the electronic structure characteristics of the two isomers has been addressed for pointing out differences in absorption and emission properties. The geometries and electronic structures are investigated at B3LYP and CIS levels for ground and excited states, respectively. At the TD-DFT and PCM levels, 1–4 give rise to absorptions at 329, 346, 355 and 347 nm, respectively, and phosphorescent emissions at 377, 461 and 405 nm for 1–3, respectively. The transitions of 1–2 are attributed to [d(Ir) + π(phenyl)] → [π*(pyrazolyl)] charge transition, whereas 3–4 are related to [d(Ir) + π(phenyl)] → [π*(pyrazolyl) + π*(dpm)]. The reorganization energies computed for hole (λ_hole) except 2 are smaller than that of N,N′-diphenyl-N,N′-bis(1,1′-biphenyl)-4,4′-diamine which is a typical hole transport material. Fac-Ir(ppz)₃ is the most efficient electron blocking material among the four complexes.