Nickel(0)/N-heterocyclic carbene complexes catalysed arylation of aromatic diamines

Nickel complexes of N-heterocyclic carbenes were examined for effecting C–N coupling reactions between aromatic diamines and aryl chlorides of varying electron density. The Ni(0) · 2IPr (IPr = N,N′-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) complex associated to t-BuONa allowed N,N′-diarylation at 100 °C in 1,4-dioxane with excellent yields. Selective monoarylation of diamines could be performed in THF at 65 °C.     

Carbazole-modified blue light-emitting copolymers with the backbones integrated by diphenyloxadiazole,fluorene, and triphenylamine

Two new blue light-emitting polymers, poly{[2,5-bis(4-phenylene)-1,3,4-oxadiazole]-[9,9-dihexylfluorene-2,7-diyl]-[N-(4-(9H-carbazol-9-yl)phenyl)-N,N-bis(p-phenylene)aniline]} (POFPA) and poly{[2,5-bis(4-phenylene)-1,3,4-oxadiazole]-[9,9-dihexylfluorene-2,7-diyl]-[4-(3,6-(di-9H-carbazol-9-yl)-9H-carbazol-9-yl)-N,N-bis(p-phenylene)-aniline]} (POFCPA), were synthesized by Suzuki coupling reactions. By GPC analysis against a linear polystyrene standard POFPA and POFCPA were found to have M_n of 1.68 × 10⁴ and 3.70 × 10³, respectively. In contrast to POFPA, the main absorption peak of POFCPA in dilute toluene solution was blue-shifted by Δλ = 26 nm owing to its backbone of relatively shorter π-conjugation length and more carbazole units in side chain. The absolute fluorescence quantum yield (Φ_f) of POFCPA in dilute toluene solution was determined as 73%, much higher than that of POFPA (Φ_f ≈ 58.9%) measured under the same conditions. An electroluminescence device based on POFCPA displays a stable blue emission having color coordinates of (0.15, 0.20), a maximum brightness of 4762 cd/m², and a maximum current efficiency of 1.79 cd/A. By using this polymer as the host material doped with 1 wt.% 4,4′-bis[2-(4-(N,N-diphenylamino)phenyl)vinyl]biphenyl, the achieved highest brightness, maximum current efficiency and maximum power efficiency are 13,613 cd/m², 3.38 cd/A, and1.84 lm/W, respectively.     

Synthesis and characterisation of Fe6 and Fe12 clusters using bicine

Reaction of bicine {BicH₃, N,N-bis(2-hydroxyethyl)glycine} with an Fe(III) oxo-centered pivalate triangle in MeCN in the presence of Et₂NH yields [Et₂NH₂]₂[Fe₆O₂(OH)₂(Bic)₂(O₂CCMe₃)₈], which possesses an S = 5 ground state.Changing the base to NaOMe produces [Fe₁₂O₄(Bic)₄(HBic)₄(O₂CCMe₃)₈], which contains two Fe₆ units bridged by the carboxylate arms from the bicine ligands. The complex displays strong antiferromagnetic coupling leading to an S = 0 ground state.     

Embedding of Al nanoparticle in Al2O3 matrix by electron beam

Embedding structures of a metal nanoparticle in an oxide matrix were first achieved by electron beam irradiation. In the system of Al/α-Al₂O₃. Al nanoparticles derived from θ-Al₂O₃ migrated and embedded in α-Al₂O₃ matrix having epitaxy relation, {1 1 2̄ 0}α-Al₂O₃//{2 0 0} Al. The driving force of the embedding is momentum transfer from electrons or ions to Al atoms of nanoparticles in the pole piece of transmission electron microscopy.     

Measurement and correlation of (vapor + liquid) equilibria for the {2-propoxyethanol (C3E1) + n-hexane} and the {2-propoxyethanol (C3E1) + n-heptane} systems

2-Propoxyethanol (C₃E₁) is one of nonionic surfactants which are a particularly interesting class of substances due to both inter-molecular and intra-molecular association. Binary (vapor + liquid) equilibrium data were measured for {2-propoxyethanol (C₃E₁) + n-hexane} and {2-propoxyethanol (C₃E₁) + n-heptane} systems at temperatures ranging from (303.15 to 323.15) K. A static apparatus was used in this study. The experimental data were correlated well with a lattice fluid equation of state that combines the multi-fluid non-random lattice fluid model with Veytsman statistics for (intra + inter)-molecular association.     

Glass transition behaviour of the quaternary ammonium type ionic liquid, {[DEME][I] + H2O} mixtures

By a simple DTA system, the glass transition temperatures of the quaternary ammonium type ionic liquid, {N,N-diethyl-N-methyl-N-(2-methoxyethyl) ammonium iodide, [DEME][I] + H₂O} mixtures after quick pre-cooling were measured as a function of water concentration (x mol% H₂O). Results were compared with the previous results of {[DEME][BF₄] + H₂O} mixtures in which double glass transitions were observed in the water concentration region of (16.5 to 30.0) mol% H₂O. Remarkably, we observed the double glass transition phenomenon in {[DEME][I] + H₂O} mixtures too, but the two-T_gs regions lie towards the water-rich side of (77.5 to 85.0) mol% H₂O. These clearly reflect the difference in the anionic effect between ${\text{BF}}_4^{-}$ and I^? on the water structure. The end of the glass-formation region of {[DEME][I] + H₂O} mixtures is around x = 95.0 mol% H₂O, and this is comparable to that of {[DEME][BF₄] + H₂O} mixtures (x = 96.0 mol% H₂O).     

Effect of ionic liquid 1-methylimidazolium chloride on the vapour liquid equilibrium of water,methanol, ethanol,and {water + ethanol} mixture

Measurements of vapour pressure data were conducted using a quasi-static ebulliometer for systems containing water, methanol, ethanol, and a mixture of {water + ethanol} in the presence of an ionic liquid (IL), namely, 1-methylimidazolium chloride ([MIm]Cl), wherein the IL-content ranged from w₂ = (0.10 to 0.50). The vapour pressure data of IL-containing binary systems were correlated by the NRTL model with an overall average absolute relative deviation (AARD) of 0.0103, and the resulting binary parameters were used to predict the vapour pressures of a ternary system {water + ethanol + [MIm]Cl} with an AARD less than 0.0077. Further, the isobaric vapour liquid equilibria (VLE) for the ternary system {water + ethanol + IL} with IL-content of w₃ = (0.10, 0.30, and 0.50) for [MIm]Cl and x₃ = 0.15 for [MIm]Cl, [C₄MIm]Cl, and [C₆MIm]Cl were predicted at 101.3 kPa, respectively. It is indicated that [MIm]Cl presents the strongest ability to enhance the relative volatility of ethanol to water in the mixture of {water + ethanol} than that of [C₄MIm]Cl and [C₆MIm]Cl, which is consistent with the cationic sizes and hence the ionic hydration ability. Therefore, distillation separation of the azeotrope of {water + ethanol} can be sufficiently facilitated by the addition of [MIm]Cl at a specified content.     

Phase equilibria study of the (N-octylisoquinolinium thiocyanate ionic liquid + aliphatic and aromatic hydrocarbon,or thiophene) binary systems

Binary liquid + liquid phase equilibria for 8 systems containing N-octylisoquinolinium thiocyanate, [C₈iQuin][SCN] and aliphatic hydrocarbon (n-hexane, n-heptane), cyclohexane, aromatic hydrocarbon (benzene, toluene, ethylbenzene, n-propylbenzene) and thiophene have been determined using dynamic method. The experiment was carried out from room temperature to the boiling-point of the solvent at atmospheric pressure. For the tested binary systems the mutual immiscibility with an upper critical solution temperature (UCST) for {IL + aliphatic hydrocarbon, or thiophene} were observed. The immiscibility gap with lower critical solution temperature (LCST) for the {IL + aromatic hydrocarbon} were determined. The parameters of the LLE correlation equation for the tested binary systems have been derived using NRTL equation. The phase equilibria diagrams presented in this paper are compared with literature data for the corresponding ionic liquids with N-alkylisoquinolinium, or N-alkylquinolinium cation and with thiocyanate – based ionic liquids. The influence of the ionic liquid structure on mutual solubility with aliphatic and aromatic hydrocarbons and thiophene is discussed.     

Phase equilibria study of the binary systems (ionic liquid + thiophene): Desulphurization process

(Solid + liquid) equilibria (SLE) and (liquid + liquid) equilibria (LLE) for the binary systems: {ionic liquid (IL) N-butyl-4-methylpyridinium tosylate (p-toluenesulfonate) [BM⁴Py][TOS], or N-butyl-3-methylpyridinium tosylate [BM³Py][TOS], or N-hexyl-3-methylpyridinium tosylate [HM³Py][TOS], or N-butyl-4-methylpyridinium bis{(trifluoromethyl)sulfonyl}imide [BM⁴Py][NTf₂], or 1,4-dimethylpyridinium tosylate [M^1,4Py][TOS], or 2,4,6-collidine tosylate [M^2,4,6Py][TOS], or 1-ethyl-3-methylimidazolium thiocyanate [EMIM][SCN], or 1-butyl-3-methylimidazolium thiocyanate [BMIM][SCN], or 1-hexyl-3-methylimidazolium thiocyanate [HMIM][SCN], or triethylsulphonium bis(trifluoromethylsulfonyl)imide [Et₃S][NTf₂] + thiophene} have been determined at ambient pressure. A dynamic method was used over a broad range of mole fractions and temperatures from (270 to 390) K. In the case of systems (pyridinium IL, or sulphonium IL + thiophene) the mutual immiscibility with an upper critical solution temperature (UCST) was detected at the very narrow and low mole fraction of the IL. For the binary systems containing (imidazolium thiocyanate IL + thiophene), the mutual immiscibility with the lower critical solution temperature (LCST) was detected at the higher mole fraction range of the IL. The basic thermal properties of the pure ILs, i.e. melting and glass-transition temperatures as well as the enthalpy of fusion have been measured using a differential scanning microcalorimetry technique (DSC). The well-known NRTL equation has been used to correlate experimental SLE/LLE data sets.     

Structure and magnetic properties of a novel copper diphosphonate with pillared layered structure:: Cu2(H2O)2{O3PCH2N(C2H4)2NCH2PO3}

Compound Cu₂(H₂O)₂{O₃PCH₂N(C₂H₄)₂NCH₂PO₃} (1) has a pillared layered structure in which the organic groups of N,N′-piperazinebis(methylenephosphonate) are sandwiched between the inorganic layers. Compared with other copper phosphonates with layered or pillared layered structures, the inorganic layer in 1 is unique in that each {CPO₃} tetrahedron is corner-shared with three {CuO₄N} square pyramids through three oxygen donors. Ferromagnetic interactions are mediated between the metal centers. Crystal data: Pbca, a=10.0830(16) Å, b=9.4517(15) Å, c=13.218(2) Å, V=1259.7(3) Å³, Z=4.     

Imidazol(in)ium-2-carboxylates as N-heterocyclic carbene precursors in ruthenium–arene catalysts for olefin metathesis and cyclopropanation

Five imidazol(in)ium-2-carboxylates bearing cyclohexyl, mesityl, or 2,6-diisopropylphenyl substituents on their nitrogen atoms were prepared from the corresponding N-heterocyclic carbenes (NHCs) by reaction with carbon dioxide. They were characterized by IR and NMR spectroscopies, and by TGA. Their ability to act as NHC precursors for in situ catalytic applications was probed in ruthenium-promoted olefin metathesis and cyclopropanation reactions. When visible light induced ring-opening metathesis polymerization of cyclooctene or cyclopropanation of styrene with ethyl diazoacetate were carried out at 60 °C in the presence of [RuCl₂(p-cymene)]₂, the NHC · CO₂ adducts and their NHC · HX counterparts (X = Cl, BF₄) displayed similar activities. When metathesis polymerizations were performed at room temperature, the carboxylates proved far superior to the corresponding imidazol(in)ium acid salts. They displayed the same level of activity as the preformed RuCl₂(p-cymene)(IMes) complex, whereas the combination of NHC · HX and KO-t-Bu were almost totally inactive. Results obtained for cyclopropanation reactions at room temperature did not show such a large discrepancy of behavior between the two types of adducts.     

Spin density distribution in oxamato-type transition metal complexes

The spin density distribution of the paramagnetic [ⁿBu₄N]₂[Cu(dana)] dana = N,N′-(naphthalene-2,3-diyl)-bis(oxamato) has been derived from angular dependent electron paramagnetic resonance measurements at room temperature. The results indicate a noticeable spin density transfer from the central metal to the coordinated N and O atoms. Quantum chemical studies using density functional theory reinforce the results.     

Phase behavior of ternary mixtures {aliphatic hydrocarbon + aromatic hydrocarbon + ionic liquid}: Experimental LLE data and their modeling by COSMO-RS

Separation of aromatic and aliphatic hydrocarbons is a complex process in the petrochemical industry due to overlapping boiling points and azeotrope formation. In this paper, liquid extraction of aromatic compounds (toluene and ethylbenzene) from aliphatic compounds (hexane and cyclohexene) using ionic liquids (1-butyl-3-methylimidazolium methylsulfate, BMimMSO₄, 1-propyl-3-methylimidazolium bis{trifluoromethylsulfonyl}imide, PMimNTf₂, and 1-butyl-3-methylimidazolium bis{trifluoromethylsulfonyl}imide, BMimNTf₂) as solvent was studied. (Liquid + liquid) equilibrium (ELL) data for the ternary systems {hexane (1) + ethylbenzene (2) + BMimMSO₄, or BMimNTf₂, or PMimNTf₂ (3)}, {hexane (1) + toluene (2) + BMimMSO₄ (3)} and {cyclohexene (1) + ethylbenzene (2) + BMimMSO₄ (3)} were experimentally determined at T = 298.15 K and atmospheric pressure. Moreover, an analysis of the influence of the structure of each compound on the phase behavior was also carried out. The ability of the studied ILs to separate aromatic from aliphatic compounds was evaluated in terms of the solute distribution ratio, β, and the selectivity, S. The Non Random Two-Liquid (NRTL) and UNIversal QUAsiChemical (UNIQUAC) thermodynamic models were used to correlate the experimental LLE data. Furthermore, the COnductor-like Screening MOdel for Real Solvents (COSMO-RS) was applied to predict the (liquid + liquid) equilibrium. The suitability of this model to describe the phase behavior of the studied mixtures was evaluated comparing the experimental and calculated data.     

Intramolecularly donor-stabilized silenes: Part 6. The synthesis of 1-[2,6-bis(dimethylaminomethyl)phenyl]silenes and their reaction with aromatic aldehydes

The intramolecularly donor-stabilized silenes ArR¹SiC(SiMe₃)₂ (3a–d) (3a: R¹ = Me; 3b: R¹ = t-Bu; 3c: R¹ = Ph; 3d: R¹ = SiMe₃; Ar = 2,6-(Me₂NCH₂)₂C₆H₃) were prepared by treatment of the (dichloromethyl)oligosilanes (Me₃Si)₂R¹Si–CHCl₂ (1a–d), with 2,6-bis(dimethylaminomethyl)phenyllithium (molar ratio 1:2). For 3c and 3d, X-ray structural analyses were performed indicating that only one dimethylamino group of the tridentate ligand is coordinated to the electrophilic silene silicon atoms, i.e., the central silicon atoms are tetracoordinated. The N → Si donation leads to pyramidalization at the silene silicon atoms; the configuration at the silene carbon atoms is planar. For a chemical characterization 3a and 3c were treated with water to give the silanols ArR¹Si(OH)–CH(SiMe₃)₂ (5a,c). Studies of the reactions of 3a and 3c with benzaldehyde, 4-chlorobenzaldehyde or 4-methoxybenzaldehyde, respectively, revealed an unexpected reaction path leading to the substituted 2-oxa-1-sila-1,2,3,4-tetrahydronaphthalenes 12a, 12c, 13 and 14. Both 12a and 12c were structurally characterized by X-ray analyses. The formation of these six-membered cyclic compounds, which is discussed in detail, gives support to a dipolar mechanism for the general reaction of silenes with carbonyl derivatives.     

Synthesis,characterization and fluorescence properties of hexanuclear zinc(II) complexes

Two hexanuclear zinc(II) complexes, [Zn₆(L¹)₂(μ₂-OH)₂(μ₂-CH₃COO)₈] · CH₃CN (1 · CH₃CN) and [Zn₆(L²)₂(μ₂-OH)₂(μ₂-CH₃COO)₈] · 4CH₃CN (2 · 4CH₃CN), where HL¹ = 4-methyl-2,6-bis(cyclohexylmethyliminomethyl)-phenol and HL² = 4-methyl-2,6-bis(1-naphthalylmethyliminomethyl)-phenol, have been synthesized and characterized by elemental analysis, FT-IR and fluorescence spectroscopic methods, and by X-ray diffraction analysis. In the asymmetric unit of complex 1, two of the three zinc atoms have pentacoordinate geometries and the other is tetrahedrally coordinated, whereas the three distinct Zn atoms in complex 2 adopt three different coordination environments, namely distorted octahedral, trigonal bipyramidal and tetrahedral. The fluorescence properties of the ligands and complexes have been investigated.     

Phase equilibrium properties of binary aqueous solutions of benzylamine, 1,2-bis(2-aminoethoxy)ethane,or 2-[2-(dimethylamino)ethoxy]ethanol

The vapour pressures of (benzylamine + water), {1,2-bis(2-aminoethoxy)ethane + water}, or {2-[2-(dimethylamino)ethoxy]ethanol + water} binary mixtures, and pure 2-[2-(dimethylamino)ethoxy]ethanol component were measured by means of two static devices at temperatures between (283.15 and 363.15 (or 323.15)) K. The data were correlated with the Antoine equation. From these data, excess Gibbs functions (G^E) were calculated for several constant temperatures and fitted to a fourth-order Redlich–Kister equation using the Barker’s method. The (benzylamine + water) binary mixture exhibits positive deviations in G^E for (303.15 < T/K < 323.15) and a sinusoidal shape in G^E for T > 323.15 K over the whole composition range. The aqueous 1,2-bis(2-aminoethoxy)ethane or {2-[2-(dimethylamino)ethoxy]ethanol + water} solutions exhibit negative deviations in G^E for all investigated temperatures over the whole composition range.     

Ferromagnetic interaction in iron(II)–bis-Schiff base complexes

The preparation and magnetic properties of three Fe(II)–bis-Schiff base complexes, [Fe₂(L1)2(4,4′-bpy)] · MeOH (1), [Fe(L2)(EtOH)] (2) and [Fe(L3)(MeOH)] (3) (L1 = N,N′-bis(2-hydroxy-1-naphthaldehyde)-1,2-phenylenediimine; L2 = N,N′-bis(salicylidene)-1,2-phenylenediamine; L3 = N,N′-bis(5-Cl-salicylidene)-1,2-phenylenediamine; 4,4′-bpy = 4,4′-bipyridine) are reported. X-ray single crystal structure analyses for 1–3 reveal that 1 shows a dinuclear Fe(II)–bis-Schiff base complex bridged by 4,4′-bpy, while 2 and 3 show mononuclear structures. Molecular packing of 2 shows a uniform one-dimensional chain structure through hydrogen bonds and Fe?π interaction and that of 3 indicates significant π–π interaction to form a dimmer structure. The χT–T plots of 1–3 show all ferromagnetic interaction at low temperature. The origin of the ferromagnetic interaction observed in 2 is tentatively ascribed to the dimer formation through Fe?π interaction at low temperature.     

Aqueous solutions of tris(1,2-diaminoethane)cobalt(III) chloride and tris(1,3-diaminopropane)cobalt(III) chloride atT = 278.15 K. Enthalpy of dilution

The enthalpies of dilution of aqueous solutions of {Co(en)₃}Cl₃and {Co(tn)₃}Cl₃(where en =  1,2-diaminoethane andtn =  1,3-diaminopropane) have been measured up to m =  1 mol · kg ^− 1at T =  278.15 K and atmospheric pressure with an isoperibol calorimeter by the long-jump method. Relative apparent molar enthalpies L_φ,mhave been extracted from an empirical polynomial of the molality square root. Previously reported data at T =  298.15 K are compared with the new experimental dilution results. A noticeable decrease in L_φ,mwas observed at every experimental concentration when temperature diminished from 298.15 K to 278.15 K. An inversion in the relative layout for the L_φ,mcurves of aqueous {Co(en)₃}Cl₃and {Co(tn)₃}Cl₃was also found.     

Excess molar volumes,and excess molar enthalpies of (N-methyl-2-pyrrolidinone + an ether ) at the temperature 298.15 K

Excess molar volumes V_m^E have been calculated from measured density values over the whole composition range at T =  298.15 K and atmospheric pressure for six { N -methyl-2-pyrrolidinone  +  1,1-dimethylethyl methyl ether, or dipropyl ether, or 1,1-dimethylpropyl methyl ether, or diisopropyl ether, or dibutyl ether, or dipentyl ether}. Excess molar enthalpiesH_m^E were also measured for five { N -methyl-2-pyrrolidinone  +  1,1-dimethylethyl methyl ether, or dipropyl ether, or 1,1-dimethylpropyl methyl ether, or diisopropyl ether, or dibutyl ether} at T =  298.15 K and atmospheric pressure. The results are discussed in terms of intermolecular associations. The experimental results have been correlated with the UNIQUAC and NRTL equations.     

Synthesis of palladium–biscarbene complexes derived from 1,1′-methylenebis(1,2,4-triazole) functionalized in the methylene bridge

Palladium–biscarbene complexes derived from N,N′-bis(1,2,4-triazol-1-yl)methane, which bear an alkyl chain functionalized with a hydroxyl group, have been synthesized ([Pd(L1)Br₂] (6) and [Pd(L1)I₂] (7) [L1 = 1,1′-(3-hydroxypropylidene)bis(4-butyl-4,5-dihydro-1H-1,2,4-triazol-5-ylidene)]). Each product is obtained as a non-equimolecular mixture of two conformers. The hydroxyl group has been replaced by bromide and methanesulphonate and ( [Pd(L2)Br₂] [L2 = 1,1′-(3-bromopropylidene)bis(4-butyl-4,5-dihydro-1H-1,2,4-triazol-5-ylidene)] (9)) and ([Pd(L3)Br₂] [L3 = 1,1′-(3-methanesulphonyloxypropylidene)-bis(4-butyl-4,5-dihydro-1H-1,2,4-triazol-5-ylidene)] (10)) were obtained, respectively, as mixtures of conformers. All compounds consist of a six-membered metallacyclic structure in a boat conformation. Major conformers present the functionalized chain in the axial position, while in minor conformers it is located in the equatorial position.