Ru(II) complexes containing dihydro-1,1,3,3-tetramethyl-7,8-diazacyclopenta[1]phenanthren-2-ol ligand: Synthesis and their electrochemiluminescent characteristics

A series of new ruthenium(II) complexes containing dihydro-1,1,3,3-tetramethyl-7,8-diazacyclopenta[1]phenanthren-2-ol (DTDP-OH) ligand, such as [Ru(DTDP-OH)_n(L)_3−n]²⁺ (L = 2,2′-bipyridyl (bpy), o-phenanthroline (o-phen), 2,2′-bipyridine-4,4′-dicarboaldehyde (bpy-(CHO)₂), 1,3-dihydro-1,1,3,3-tetramethyl-7,8-diazacyclopenta[1]phenanthren-2-one(DTDP), n = 1, 2, 3) were synthesized and their electrochemical and photophysical properties were studied. The synthesized Ru(II) complexes containing the DTDP-OH ligand showed strong MLCT absorptions at 420–487 nm. All the synthesized Ru(II) complexes containing the DTDP-OH ligand exhibited more intensive ECL emissions than the well-known [Ru(o-phen)₃]²⁺ does. In particular, the ECL intensities of [Ru(DTDP-OH)₂(o-phen)]²⁺ and [Ru(DTDP-OH)₂(bpy-(CHO)₂)]²⁺ were observed to be more than 2-fold greater than that of [Ru(o-phen)₃]²⁺.     

Ionic liquid-stabilized nanoparticles of charge transfer-based conductors

Well-dispersed nanoparticles of molecule-based conductors, namely TTF·TCNQ and TTF[Ni(dmit)₂]₂, have been prepared in organic solution using 1-butyl-3-metylimidazolium tetrafluoroborate as a stabilizing agent. TTF·TCNQ nanoparticles (prepared at room temperature) exhibit sizes ranging from 2 to 5.5 nm, whereas those of TTF[Ni(dmit)₂]₂ (prepared at ?80 °C) are larger (sizes in the 16–45 nm range). Nanoparticle powders have been characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and by transport measurements.     

Crystal growth of copper-rich ytterbium compounds: The predicted giant unit cell structures YbCu4.4 and YbCu4.25

Two new phases YbCu_4.4 and YbCu_4.25 are found as a result of careful phase diagram investigations. Between the congruent and peritectic formation of YbCu_4.5 and YbCu_3.5, respectively, the phases YbCu_4.4 and YbCu_4.25 are formed peritectically at 934(2) °C and 931(3) °C.Crystal growth was realised using a Bridgman technique and single crystalline grains of about 50–100 μm were analysed by electron diffraction and single crystal X-ray diffraction. Due to the only slight differences in both compositions and formation temperatures the growth of larger single crystals of a defined phase is challenging. The compounds YbCu_4.4 and YbCu_4.25 fit in ?ernýs [J Solid State Chem 2003;174:125] building principle {(RECu₅)_n·(RECu₂)} where RE = Yb with n = 4 and 3. YbCu_4.4 and YbCu_4.25 are based on AuBe₅/MgCu₂-type substructures and contain approximately 4570 and 2780 atoms per unit cell. The new phases close the gap in the series of known copper-rich rare-earth compounds for n = 1, 2 (DyCu_3.5, DyCu_4.0) and n = 5 (YbCu_4.5, DyCu_4.5).     

Conductive complexes of [Ni(dmid)2] with TTF,TMTTF, and ET

Three charge-transfer salts of [Ni(dmid)₂]⁻ (dmid: 1,3-dithiol-2-one-4,5-dithiolate)—TMTTF[Ni(dmid)₂], TTF_x[Ni(dmid)₂] and ET_x[Ni(dmid)₂] (TMTTF: tetramethyl-tetrathifulvalene, TTF: tetrathifulvalene, ET: bis(ethylenedithio)-tetrathiafulvalene) are prepared and characterized. The TMTTF[Ni(dmid)₂] complex has a structure with mixed packs is formed by cations and anions, which alternate each other with subsequent shift. This compound is semiconductor with the room-temperature conductivity of 2.2 × 10⁻³ Ω⁻¹ cm⁻¹. The TTF_x[Ni(dmid)₂] and ET_x[Ni(dmid)₂] complexes have a highest conductivity: σ_RT 1.86 and 0.54 Ω⁻¹ cm⁻¹, respectively.     

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.     

Synthesis of 2-phenylquinoline-based ambipolar molecules containing multiple 1,3,4-oxadiazole spacer groups

A series of donor–acceptor type ambipolar electroluminescence dyes with the general structure PQ(OXD)_nT (where n = 1, 2 and 3) were prepared, in which PQ is 2-phenylquinoline, T is diphenylamine which constituted the hole transporting triphenylamine moiety with an adjacent phenyl ring, and OXD is an electron transporting 2-phenyl-1,3,4-oxadiazole repeating unit. The compounds fluoresced bluish green to green hue in solid-state, exhibited a positive solvatochromism in solution and their quantum efficiency decreased rapidly with increase in n. The materials are thermally stable with glass transition temperature (T_g) ranging from 83 °C (n = 1) to 130 °C (n = 3). Cyclic voltammetry studies indicated the HOMO remained relatively unchanged with n while the LUMO decreased (away from the vacuum level) with an increase in the number of OXD. For single layer homojunction OLEDs, highest efficiency was obtained when n = 1 (max luminous 3300 cd/m² and current efficiency 0.9 cd/A), whereas for multilayer heterojunction OLEDs, best results was achieved for compounds with n = 1 or 2 assuming the role of the HT layer (over 8200 cd/m² max and 2.0 cd/A). Formation of exciplexes led to significant red-shift and lower emission efficiency for the compound with n = 3.     

Synthesis,characterization, and dc conductivity of hydrogen-bonding dibenzotetrathiafulvalene (DBTTF) based salts

The synthesis, characterization, and dc conductivity of organic conductors, 1-[2-(1,3-benzodithiol-2-ylidene)-1,3-benzodithiol-5-yl]ethylammonium tetrafluoroborate ([DBTTFCH(Me)NH₃⁺]BF₄^?) and 1-[2-(1,3-benzodithiol-2-ylidene)-1,3-benzodithiol-5-yl]ethylammonium bromide ([DBTTFCH(Me)NH₃⁺]Br^?) salts are presented. These salts are prepared by mixing the corresponding primary amine and Brønsted acid in a one-to-one ratio without electrochemical oxidation. The change in the electronic state of insulating DBTTFCH(Me)NH₂ into conductive [DBTTFCH(Me)NH₃⁺]X^? (X = BF₄ and Br) salts and the carrier generation upon salt formation were confirmed by diffuse reflectance (UV–vis) and ESR spectra. The concentration of localized radicals is estimated to be 1 radical/3.3 units and 1 radical/1.8 units for BF₄ and Br salts, respectively. The possible carrier generation mechanism is proposed by ¹H NMR and ESI-TOF-MS spectroscopic analyses. The dc conductivity and the activation energy are σ_rt = 2.3 × 10^?3 S/cm with 0.24 eV for the BF₄ salt, and σ_rt = 1.3 × 10^?3 S/cm with 0.21 eV for the Br salt.     

Charge transfer driven surface segregation of gold atoms in 13-atom Au–Ag nanoalloys and its relevance to their structural,optical and electronic properties

The structural, optical and electronic properties of 13-atom Ag–Au nanoalloys are determined by a combination of global optimization using semi-empirical potentials and density functional theory calculations. A family of Au surface-segregated structures are found for core–shell Ag_nAu_13−n (n = 1, 2, 3, 5, 7, 8, 9, 12) and hollow Ag_nAu_13−n (n = 4, 6, 10, 11) clusters, whose stability is enhanced by directional charge transfer. The atomic ordering in core–shell structures is related to the electric dipole moment and odd-numbered surface Au-atom clusters have high moments. Their ferroelectric and ferromagnetic properties provide a potential approach for tailoring their surface plasmonic modes.     

Deformation twinning in Ni2MnGa

Deformation twinning is investigated in the martensitic phase of a Ni_46.75Mn₃₄Ga_19.25 (at.%) alloy. X-ray and electron diffraction are used to establish the crystallography of the non-modulated tetragonal martensite, and transmission electron microscopy is employed to deduce the twinning parameters. It is convenient to define the twinning parameters with respect to a “monoclinic” unit cell, designated 2M: then K₁, η₁, K₂, and η₂ are (0 0 1), [1 0 0], (1 0 0), and [0 0 1] respectively. The Burgers vector of the active twinning disconnections is close to 1/6[1 0 0] and the disconnections are associated with steps of height d₍₀₀₂₎. These defects are expected to be highly mobile since their motion does not require atomic shuffling. It is shown that periodic arrangements of two layer twins produce modulated crystal structures, such as 14M.     

Crystal structure of [NBu4]2[Pd2{C4(COOMe)4}2(μ-OH)2] determined ab initio by charge flipping

The crystal structure of bis(tetra-n-butylammonium)bis(μ₂-hydroxo)-bis(1,2,3,4-tetrakis(methoxycarbonyl)-1,3-butadiene-1,4-diyl)-di-palladium, [NBu₄]₂[Pd₂{C₄(COOMe)₄}₂ (μ-OH)₂], was determined ab initio by X-ray single-crystal diffractometry using the charge flipping method. The compound crystallizes in the monoclinic system with P2₁/c as space group and the following cell parameters: a = 12.8481(6) Å, b = 63.744(3) Å, c = 16.6102(8) Å, β = 111.943(10). The asymmetric unit is formed by two molecules, and the unit cell contains eight molecules (Z = 8) giving a density of 1.369 g cm^?3. The coordination around the Pd(II) atoms is approximately planar, the methoxycarbonyl groups at the α and β positions relative to Pd are perpendicular and parallel to the palladacycle ring, respectively, and the {Pd(μ-O)}₂ core has a bent conformation. The structure closely resembles the features reported previously for other palladacyclopentadiene complexes.     

Titanium-supported Ce-, Zr-containing oxide coatings modified by platinum or nickel and copper oxides and their catalytic activity in CO oxidation

A combination of plasma electrolytic oxidation (PEO) and impregnation techniques followed by annealing in air has been used to obtain composites Pt/nZrO₂ + pTiO₂/Ti, Pt/nZrO₂ + pTiO₂ + zCeO_x/Ti, NiO + CuO/nZrO₂ + pTiO₂/Ti, NiO + CuO/nZrO₂ + pTiO₂ + zCeO_x/Ti with different zirconium and titanium contents and ZrO₂/TiO₂ phase ratio. The composites have been investigated by means of XRD, XPS and SEM/XSA methods. According to the XPS data, the platinum content on the coating surface is ~ 0.4 at.%, whereas the XSA measurements have shown that the nickel and copper contents in coatings attain 16 and 8 at.%, respectively, depending on the initial oxide coatings composition. Nickel and copper oxides form either extended islets or solid layers (“crusts”) on the coating surface. Both the composites promoted with platinum and those with the “crust” built from nickel and copper oxides are active in CO oxidation at the temperatures above 200 °C and 300 °C, respectively.     

Anisotropic elastic and thermal properties of the double perovskite slab–rock salt layer Ln2SrAl2O7 (Ln = La,Nd, Sm,Eu, Gd or Dy) natural superlattice structure

The anisotropic elastic and thermal properties of layered compounds in the series Ln₂SrAl₂O₇ (Ln = La, Nd, Sm, Eu, Gd or Dy) are calculated from first principles using density functional theory combined with the Debye quasi-harmonic approximation. The polycrystalline values of the elastic constants and bulk, shear and Young’s moduli are consistent with those determined experimentally. All compounds in the compositional series have weakly anisotropic elastic and thermal properties. For instance, thermal expansion in the [0 0 1] direction of the tetragonal unit cell is slightly larger than along the [1 0 0] or [0 1 0] directions for most Ln₂SrAl₂O₇ compounds and the calculated in-plane thermal conductivity is always larger than that along the c-axis, parallel to the layer stacking direction.     

Structure and magnetoresistive properties of current-perpendicular-to-plane pseudo-spin valves using polycrystalline Co2Fe-based Heusler alloy films

We report current-perpendicular-to-plane giant magnetoresistance (CPP–GMR) of pseudo-spin valves (PSVs) with polycrystalline Co₂Fe(Al_0.5Si_0.5) (CFAS) and Co₂Fe(Ga_0.5Ge_0.5) (CFGG) Heusler alloy films. Strongly [0 1 1] textured polycrystalline Heusler alloy films grew on the Ta/Ru/Ag underlayer. Relatively large CPP–GMR values of ΔRA up to 4 mΩ μm² and ΔR/R up to 10% were obtained with 5 nm thick Heusler alloy films and Ag spacer layer by annealing CFAS PSV at 450 °C and CFGG PSV at 350 °C. Transmission electron microscopy revealed a flat and sharp interface between the [0 1 1] textured CFAS layers and the [1 1 1] textured Ag spacer layer. Annealing above an optimal temperature for each PSV led to reductions in MR values as a result of the thickening of the spacer layer induced by the Ag diffusion from the outer Ag layers.     

The new series of RZnGe compounds (R = rare earth element) with the YPtAs structure type

The synthesis and crystal structure of the new family of rare earth ternary equiatomic RZnGe phases are reported. The compounds are found to form for R = La to Nd, Sm, Gd to Tm, Y, all crystallizing with the hexagonal hP12-P6₃/mmc YPtAs structure type, a four-layers superstructure derivative of the AlB₂ type. No formation of the equiatomic phase has been observed for R = Lu and Sc. The unit cell parameters, as obtained by the Guinier method on polycrystalline samples, vary regularly from the La [a = 4.333(1), c = 17.017(2) Å] to the Tm homologous [a = 4.192(1), c = 15.314(2) Å]. The crystal structure has been refined for the Ce, Gd and Y compounds by single crystal data.     

Solvent-drop assisted mechanochemical synthesis of the black and green polymorphs of the tetrathiafulvalene–chloranil charge transfer salt

This work describes the synthesis of the green and black polymorphic forms of the tetrathiafulvalene–chloranil (TTF–CA) charge transfer salt as pure phases, by solvent-assisted mechanochemistry. Both materials were characterized using laboratory and high-resolution X-ray powder diffraction (XRPD), elemental analysis and scanning electron microscopy (SEM). The high-resolution XRPD pattern of the TTF–CA black polymorph was indexed with a triclinic lattice a = 10.756(5) Å, b = 11.057(4) Å, c = 6.614(2) Å, α = 101.36(2)°, β = 93.69(3)°, γ = 89.37(3)°, V = 769.6(5) Å³. The chemical stability of these phases upon heating was investigated using thermogravimetric analysis (TGA), elemental analysis and X-ray powder diffraction (XRPD), indicating that both polymorphs undergo chemical decomposition, and ruling out the transition to an air-stable high temperature polymorph.     

Analysis of electrochemical impedance of polypyrrole|sulfate and polypyrrole|perchlorate films

PPy|SO₄ and PPy|ClO₄ films have been synthesized and investigated in K₂SO₄, ZnSO₄ and NaClO₄ aqueous solutions by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and electron probe microanalysis (EPMA) methods. On the basis of obtained data and calculated impedance parameters as the potential functions, the role of different processes (diffusion of ions, double-layer charging, adsorption and charge transfer) in oxidized, partially reduced and reduced PPy films is estimated. The lowest pseudocapacitance values (from n × 10⁻⁶ to n × 10⁻⁴ μF cm⁻² for 1 μm film), independent of solution concentration, were established for PPy|SO₄ in ZnSO₄. This phenomenon is related with strongly aggravated film reduction process in the solution of double-charged cations. In the case of PPy|ClO₄ in NaClO₄ and PPy|SO₄ in K₂SO₄,where the mono-charged cations participate in redox process, the capacitance values are in the range from: n × 10⁻³ to n × 10⁻² μF cm⁻² and even somewhat higher for PPy|ClO₄ system at oxidized state. The calculated effective diffusion coefficients of ions D remain inside the range from n × 10⁻¹² to n × 10⁻¹⁴ cm² s⁻¹ for PPy|SO₄ in 0.1 M K₂SO₄ and PPy|ClO₄ in 0.1 M NaClO₄ aqueous solution. In the case of PPy|SO₄ film in ZnSO₄ solution the D values are essentially lower.     

The synthesis and characterization of new oligo(polyether)s with Schiff base type

New oligo(polyether) ligands with Schiff base type were synthesized by the reaction of diethyleneglycol bis(2-aminophenyl ether) and triethyleneglycol bis(4-aminophenyl ether) with oligosalicylaldehyde (OSA). OSA was synthesized from the oxidative polycondensation of salicylaldehyde (SA) with air in an aqueous alkaline medium at 90 °C. The products were characterized by ¹H-NMR, ¹³C-NMR, FT-IR, UV–Vis and elemental analysis. The number average molecular weight, M_n, mass average molecular weight, M_w, and polydispersity index values, PDI, of OSA, graft oligo[1,5-di(N-2-oxyphenyl-salicylidene)-3-oxapentane] (compound 4) and graft oligo[1,8-di(N-4-oxyphenyl-salicylidene)-3,6-oxaoctane] (compound 5) were found to be 1690 g mol⁻¹, 5150 g mol⁻¹, 3.05, 1100 g mol⁻¹, 5400 g mol⁻¹, 4.90 and 1100 g mol⁻¹, 5600 g mol⁻¹, 5.01, respectively. TG and DTA analyses were shown to be stable of oligo(polyether) ligands with Schiff base type against thermo-oxidative decomposition. The weight loss of oligo(polyether) ligands with Schiff base type (compounds 4 and 5) were found to be 52 and 56% at 1000 °C, respectively.     

Non-Ohmic current–voltage characteristics in the positively charged tetrathiafulvalene (TTF) molecular crystals

The mechanism of an extraordinary increase in conductivity at larger applied voltage than the critical voltage generally observed in the one-dimensional electronic systems such as tetrathiafulvalenium–tetracyanoquinodimethanide (TTF–TCNQ) is quantitatively investigated. The tunneling effects of the nondissipative diamagnetic currents between the two neighboring localized TTF unit cells and the current–voltage characteristics at low temperature process (0 K < T < 14 K) are investigated. The transition probability (P_TC) of electrons between two neighboring unit cells is estimated to be in the order of 10^?3–10^?4. The estimated density of states near the Fermi level in the Peierls distorted structures (N_PD(?_F)) on the basis of the experimental results of the current–voltage characteristics is always larger than that (N_NM(?_F)) in the normal metallic states in TTF–TCNQ molecular crystals. This result can be rationalized from the fact that the density of states near the Fermi level in the Peierls distorted states is enhanced as a result of the congestion of the energy levels. That is, the N_PD(?_F) values estimated on the basis of the tunneling effect theory suggested in this paper are well rationalized. The tunneling effects theory of the nondissipative diamagnetic currents is compared with the incommensurate charge-density-wave (ICDW) sliding theory. According to our quantitative calculated results, the phenomena described above can be understood if we consider that such an extraordinary increase in conductivity originates from the tunneling effects of the nondissipative localized diamagnetic currents between the two neighboring unit cells.     

A blue organic emitting diode derived from new styrylamine type dopant materials

We have designed and synthesized new dopant materials based on the styrylamine moiety, 4-[(1,2-diphenyl)-4′-(N,N-diphenyl-4-vinylbenzenamine)]biphenyl (4) and 4-[(1,2-diphenyl)-4′-(N,N-diphenyl-4-vinylbenzenamine)]terphenyl (8). Blue OLEDs were obtained from new styrylamine dopant materials and compared with those of blue dopant bis[4-(di-p-N,N-diphenylamino)styryl]stilbene (DSA-Ph) and diphenyl[4-(2-terphenyl vinyl)phenyl]amine (R-BD). The ITO/DNTPD/NPB/MADN:dopant/Alq₃/Al-LiF device obtained from 4 shows blue EL spectrum at 469 nm and high efficiency 3.02 cd/A at 7 V. 8 also shows blue EL spectrum around λ_max = 468 nm, efficiency of 3.51 cd/A and a current density of 25.94 mA/cm² (855.7 cd/m²) at 7 V.     

Ta4AlC3: Phase determination,polymorphism and deformation

Ta₄AlC₃, a new member of the M_n+1AX_n-phase family, has been synthesized and characterized (n = 1–3; M = early transition metal; A = A-group element; and X = C and/or N). Phase determination by Rietveld refinement of synchrotron X-ray diffraction data shows that Ta₄AlC₃ belongs to the P6₃/mmc space group with a and c lattice parameters of 3.10884  ± 0.00004 Å and 24.0776 ± 0.0004 Å, respectively. This is shown to be the α-polymorph of Ta₄AlC₃, with the same structure as Ti₄AlN₃. Lattice imaging by high-resolution transmission electron microscopy demonstrates the characteristic MAX-phase stacking of α-Ta₄AlC₃. Three modes of mechanical deformation of α-Ta₄AlC₃ are observed: lattice bending, kinking and delamination.