Ruthenium catalyzed asymmetric transfer hydrogenation based on chiral P,N,O Schiff base ligands and crystal structure of a ruthenium(II) complex bearing chiral P,N,O Schiff base ligands

A ruthenium catalyst, generated in situ by heating the chiral P,N,O Schiff base ligand L (L = (S)-Ph₂PC₆H₄CNCHPhCH₂OH) with Ru(DMSO)₄Cl₂ in 2-propanol, is active for asymmetric transfer hydrogenation with best enantioselectivity up to 81%. A ruthenium complex of formula RuL₂Cl₂ is prepared and its crystal structure revealed that the two chiral P,N,O Schiff ligands are in meridional configuration. This complex is also an active catalyst for asymmetric transfer hydrogenation. However, the ‘[Ru(DMSO)₄]Cl₂ + chiral P,N,O ligand’ protocol displays better enantioselectivity.     

Deposition-environment-dependent structural and magnetic property modification of [111]-oriented epitaxial CoFe2O4 films

We examined the magnetic, structural, and chemical properties of CoFe₂O₄ films deposited on Al₂O₃ substrates using RF-magnetron sputtering under Ar and Ar + O₂ environments. Perpendicular magnetic anisotropy with large magnetization was observed in the case of the film deposited under the Ar + O₂ environment. However, no significant anisotropy appeared in the film deposited under the Ar environment. Interestingly, depth-dependent X-ray photoelectron spectra showed nearly identical stoichiometric ratios of Co/Fe and oxygen vacancies regardless of the deposition environment. Structurally, high-quality crystallinity with in-plane compressive strain, and lower surface and interfacial roughness were induced in the film deposited under the Ar + O₂ environment. Cross-sectional transmission electron microscopy and X-ray reflectivity measurements showed that oxygen not only suppressed the deposition rate but also increased the electron density of the film, resulting in better crystallinity. Hence, the presence of oxygen during deposition should be considered as one of the essential parameters for improving the structural and magnetic properties of ferrite films.     

A potassium and cadmium coordination polymer connected by two kinds of coordination modes of 4,5-dicyanoimidazole ligands: Synthesis,crystal structure and fluorescent properties of {[K[Cd(dci)2(H2O)2]6]Cl}n

A novel heteronuclear cooordination polymer containing potassium and cadmium, {[K[Cd(dci)₂(H₂O)₂]₆]Cl}_n (1) (Hdci = 4,5-dicyanoimidazole), has been synthesized and characterized with the aid of elemental analysis, fluorescence spectroscopic studies and single-crystal X-ray diffraction. In compound 1, half of dci^? anions act as bidentate bridging ligands and the other half act as tridentate bridging ligands. It is through the bridging function of dci^? ligands that K(I) and Cd(II) ions are connected and 3D coordination polymer of 1 forms. Solid-state fluorescence measurements reveal that complex 1 can emits strong purple emission band.     

Polymeric coordination system of [Ag2(NO3)2L]n [L = 1,4-bis((cyclohexylthio)acetyl)piperazine] that exhibits supramolecular isomerism with 2D and 3D frameworks

Depending on the solvents used for crystallization, silver nitrate and the flexible dithioether-type ligand incorporating piperazine diamide [L: 1,4-bis((cyclohexylthio)acetyl)piperazine] readily formed two distinct types of 2D (1) and 3D (2) coordination polymers with identical formula [Ag₂(NO₃)₂L]_n. The preparation and structural characterisation of 1 and 2 are reported as an example for the supramolecular isomerism.     

A mixed-type of azametallacrown containing [Mn6(pnhz)6(DMF)4(H2O)2] and [Mn6(pnhz)6(DMF)2(H2O)4] constructed by a flexible pentadentate ligand

A mixed-type of azametallacrown based on a flexible pentadentate N-propionyl ligand was reported, which exhibits not only the completely different arrangement of the metal centers but also diversely geometric configurations of the N-terminal ligands, and this complex can further assemble into a novel 3-D supramolecular structure using two different aza18-MC-6 as secondary building units (SBUs) via the intermolecular C–H?π, π–π and C–H?O interactions. Temperature-dependent magnetic susceptibility measurements of the title complex indicate that the complex presents significantly antiferromagnetic coupling among metal centers.     

Two 2-D 4-connected lanthanide coordination framework based on benzimidazole-5,6-dicarboxylate and acetate mixed ligands

Two 2-D polymers, [Ln(bidc)(Ac)·H₂O]_n (Ln = Tb(1), Dy(2) H₂bidc = benzimidazole-5,6-dicarboxylic acid, HAc = acetic acid), have been successfully synthesized under hydrothermal conditions at 150 °C and characterized by elemental analysis, infrared spectra and single-crystal X-ray diffraction. Single crystal X-ray diffraction analyses reveal that the two compounds are isomorphous and exhibit one new (4,4)-connected 2-nodal (4⁴·6²)(4⁴·6²) layer-like net, stabilized by the interchain hydrogen bonding N–H?O, O–H?O and π?π stacking interactions between two benzimidazole rings. 2-D layers are further connected by the interlayer O–H?O hydrogen-bonding interactions to form a 3-D supermoleculaer network. Moreover, the luminescent property of compound 1 and thermogravimetric analyses of the two complexes 1–2 are discussed in detail.     

A tetranuclear manganese oxo complex with terminal and bridging trifluoroacetate ligands: synthesis and structure of [Mn4O2(O2CCF3)8(bpy)2]

Efforts to prepare tetranuclear manganese oxo complexes that model the water oxidizing center in Photosystem II have focused largely on using unsubstituted acetate and benzoate ligands. We report the reaction of Mn(O₂CCF₃)₂, (n-Bu₄N)[MnO₄], and bipyridine in trifluoroacetic acid yields the compound [Mn₄O₂(O₂CCF₃)₈(bpy)₂]. X-ray crystallographic studies of this complex show a non-planar {Mn₄O₂}⁸⁺ center with an arrangement of bipyridine and bridging trifluoroacetate ligands that is very similar to the acetate complex [Mn₄O₂(O₂CCH₃)₇(bpy)₂]⁺ [Christou, et al. J. Am Chem. Soc. 11 (1989) 2086]. The structure differs, however, in that the coordination sites occupied previously by a bridging bidentate acetate ligand are occupied by two terminal monodentate trifluoroacetate ligands in a cis arrangement. One of the terminal trifluoroacetate ligands is hydrogen-bonded to a co-crystallized trifluoroacetic acid molecule.     

A microporous chiral metal coordination polymers: Solvothermal synthesis and structural characterization of KMn2[(L-C4H2O6)2B] · 3H2O

A microporous chiral complex KMn₂[(L-C₄H₂O₆)₂B] · 3H₂O was synthesized solvothermally in the presence of l-tartaric acid. In this framework, Mn²⁺ ions exhibit distorted octahedral coordination and the tartrate group is bonded to the B atom as a bidentate ligand via oxygen atoms of neighbouring hydroxyl groups.     

[Cu(4,4′-bipy)]2[H4P2W18O62] · 2H2O: The first three-dimensional framework based on saturated Wells–Dawson POMs modified by multi-track Cu–N coordination polymeric chains

A new double bitrack Cu–N coordination polymeric chain-modified Wells–Dawson POMs, [Cu(4,4′-bipy)]₂[H₄P₂W₁₈O₆₂] · 2H₂O (1), has been synthesized and characterized by IR, TG and single crystal X-ray diffraction. It represents the first example that saturated Wells–Dawson POMs are covalently linked by transition metal coordination polymers into a 3D structure. Additionally, its electrochemical property has been studied, undergoing three two-electron reversible redox processes.     

Synthesis of novel narrow-band-gap copolymers based on [1,2,5]thiadiazolo[3,4-f]benzotriazole and their application in bulk-heterojunction photovoltaic devices

Two novel conjugated alternating copolymers with [1,2,5]thiadiazolo[3,4-f]benzotriazole as acceptor and 9,9-dioctylfluorene or N-9’-heptadecanyl-carbazole as donors respectively, were synthesized by Suzuki polycondensation. Both of the two copolymers have nearly ideal band gaps and show excellent absorption spectra in near infrared region. Polymer solar cells based on the blends of them and [6,6]-phenyl-C₇₁ butyric acid methyl ester show excellent performance when using a water/alcohol soluble conjugated polymer as cathode interlayer, which exhibit a maximum power conversion efficiency of 3.17% with the short-circuit current density of 8.50 mA/cm², the open-circuit voltage of 0.70 V and the fill factor of 41%. Our results demonstrate that [1,2,5]thiadiazolo[3,4-f]benzotriazole is a promising acceptor unit for low band gap polymer donor materials design.     

[Ba(H2O)4(CuL)2]n: a novel coordination polymer constructed from L-bridged 1D chains via inter-chain hydrogen bonds (L=Schiff base derived from 5-bromosalicylaldehyde and glycylglycine)

A novel coordination polymer [Ba(H₂O)₄(CuL)₂]_n (where L=Schiff base derived from 5-bromosalicylaldehyde and glycylglycine) has been synthesized and characterized by X-ray crystallography. The structure reveals the formation of one-dimensional chains, which are assembled further into two-dimensional network by hydrogen bonds between the coordinated water molecules.     

Isolation and structural characterization of the first homoleptic lanthanide–zirconium oxoisopropoxide,La2Zr3O(OPri)16. Combination of an [M4O] tetrahedron with an [MO6] octahedron – A new structure type for pentanuclear alkoxide complexes

The amorphous bimetallic isopropoxides of variable composition LaZr_nO_x(OPrⁱ)_3+4n−2x, where n = 0.5–3 formed on interaction of the two homometallic isopropoxides, La₅O(OⁱPr)₁₃ and Zr(OⁱPr)₄(ⁱPrOH), in solutions in parent alcohol crystallize slowly yielding a bimetallic oxoalkoxide La₂Zr₃O(OPrⁱ)₁₆ (1). In its molecule an octahedrally coordinated zirconium atom is connected via two μ₃-OR and two μ-OR-groups with two lanthanum atoms of a tetrahedral [La₂Zr₂(μ₄-O)] aggregate. This structure type has not been previously observed in the structures of pentanuclear alkoxide aggregates. The conditions leading to formation of 1 from solutions containing the homometallic alkoxides are outlined.     

Synthesis of hyperbranched conjugated polymers based on 3-hexylthiophene,triphenylamine and benzo [c] [1,2,5] thiadiazole moieties: convenient synthesis through suzuki polymerization and impact of structures on optical properties

Novel 3-hexylthiophene-based hyperbranched conjugated polymers containing triphenylamine and benzo [c] [1, 2, 5] thiadiazole moieties were synthesized by Suzuki coupling polymerization of tris (4-bromophenyl) amine, 2,2′-(3-hexylthiophene-2,5-diyl) bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolane) and 4,7-dibromobenzo [c] [1, 2, 5] thiadiazole. Organic solvent-soluble polymers with number-average molecular weights of 24,000 and 42,000 g/mol were obtained in 54–57 % yields. Their structures, molecular weights and thermal properties were characterized via proton nuclear magnetic resonance (¹H NMR) and Fourier transform infrared (FT-IR) spectroscopies, gel permeation chromatography (GPC), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and wide-angle powder X-ray diffraction (XRD) measurements. Optical investigation by UV–vis and fluorescence spectroscopies revealed that the incorporation of the benzo [c] [1, 2, 5] thiadiazole moiety in the hyperbranched polymer structure resulted in a red-shift of the maximum absorption wavelength and an increase in the solution-photoluminescence quantum yield, indicating an extension of the conjugation length. The UV–vis, DSC and XRD results demonstrated that the aggregation of conjugated polymer chains could effectively be reduced by the hyperbranched structures and that conjugation length extension via the introduction of benzo [c] [1, 2, 5] thiadiazole units led to the coexistence of both crystalline and amorphous phases in the solid state and in solution upon addition of a non-solvent.     

Conversion of tetranuclear Ni complexes from a defect dicubane core to a [Ni4O4] cubane-like core via addition of 2-hydroxymethylpyridine: Synthesis,crystal structures,and magnetic properties

A defect dicubane-like complex, [Ni₄{(2-py)₂C(OH)O}₂{(2-py)₂C(OCH₃)O}₂ (N₃)₄]·2CH₃CN·2H₂O (1) and a cubane-like complex, [Ni₄{(2-py)₂C(OH)O}₃(hmp)₃(NO₃)]^.(NO₃)·3H₂O (2) (Hhmp = 2-hydroxymethylpyridine), were prepared by reacting NiCl₂·6H₂O with (py)₂CO, NaN₃ and NMe₄OH in MeOH/MeCN and the similar reaction exception the N₃⁻ anion replaced by multidentate chelating ligand Hhmp, respectively. X-ray analysis revealed that four Ni^2 + ions, four O atoms and two N atoms in 1 were located at the vertices of a defect dicubane; by contrast, four Ni^2 + ions and four O atoms in 2 occupied alternate vertices of a [Ni₄O₄] cubane. Magnetic studies indicated the presence of overall ferromagnetic interactions between Ni^2 + ions within both complexes.     

Li[Ni1/2Mn1/2]O2的制备及电化学性能研究

介绍了一种采用前驱体碳酸盐共沉淀法制备锂离子电池正极材料Li[Ni1/2Mn1/2]O2的工艺路线。通过对样品进行X射线衍射(XRD)测试,可知产品具有类似钴酸锂的层状结构。通过对产品进行扫描电镜(SEM)观察可以看出,产品具有规则的球形形貌,且粒径在5~10μm;电化学测试表明,材料的首次放电比容量大于170 mA.h/g,循环20次后容量保持率大于98%。     

Synthesis and resolution of 1,11-diamino-dibenzo[d,f][1,3]dioxepine: A route to new asymmetric ligands and their complexes

Reaction of 2-iodo-3-nitrophenol with methylene iodide and Ullmann intramolecular coupling of the produced 1,1′-[methylenebis(oxy)]bis[2-iodo-3-nitro]benzene afforded 1,11-dinitro-dibenzo[d,f] [1,3]dioxepine, characterized by single crystal X-ray analysis. The title diamine was obtained by reduction of the nitroderivate with hydrazine hydrate. Resolution of the enantiomers of the novel C₂-symmetric ligand can be easily obtained by use of tartaric acid. A test on the coordinating ability of the diamine has produced a complex examined by X-ray diffraction analysis.     

一维链状均苯三酸锌配合物[Zn_3(BTC)_3(H_2O)_(12)]_n的水热合成及晶体结构研究

以Zn(CH3COO)2和均苯三酸(1,3,5-苯三酸)为原料,采用水热法合成了一维链状均苯三酸锌配合物[Zn3-(BTC)3(H2O)12]n,利用元素分析、X射线单晶衍射对其结构进行了表征。该配合物属于单斜晶系,C2空间群,a=17.424(5)nm,b=12.919(5)nm,c=6.577(5)nm,β=111.968(5)°,V=1.373 0(12)nm3,Z=2,Dc=1.999 g/cm3,μ=2.707 mm-1,F(000)=840,R1=0.031 5,wR2=0.078 9。     

A novel combustion fuel for the synthesis of nanocrystalline ZnAl2O4 particles based on the thermodynamic correlations and their structural and optical studies

ZnAl₂O₄ nanocrystalline particles were prepared using the solution combustion method using a new combustion fuel, Leucine. The prepared samples' structural, microstructural–elemental composition, and optical characteristics were investigated using XRD, SEM-EDS, and UV–Visible spectroscopy. As-synthesized ZnAl₂O₄ nanoparticles are polycrystalline, with no secondary phases, and crystallized in a cubic - spinel structure. The polycrystalline nature of the prepared sample is due to the exothermicity of fuel and oxidizer, which demonstrate that the fuel utilized (Leucine) provided adequate energy for the production of nanoparticles in their as-synthesized form, as supported by adiabatic temperature through thermodynamic calculations. The thermodynamic calculations also include a universal method to estimate the specific heat capacity at constant pressure. Furthermore, even after 2 h of calcination at 600 °C, ZnAl₂O₄ exhibits a single phase with no secondary phases, indicating the material stability and single-phase nature. The crystallinity of ZnAl₂O₄ nanoparticles was observed to increase with increasing annealing temperature. SEM micrographs of as-synthesized samples exhibit the formation of dense particles, voids, and pores in the as-synthesized sample. In addition, tiny aggregates were detected on the surface of more prominent clusters, which reduced as the calcination progressed. In addition, calcined samples exhibit a greater optical reflectance than as-synthesized samples. Tauc's graphs were used to compute the optical energy bandgap. The calculated energy band gap is redshifted to that of the bulk material. The bandgap energy decreases upon calcination, suggesting that the prepared materials have a larger crystallite size or more crystallinity. Correlations were found between the T_ad, and the structural and optical properties of the prepared samples. The findings suggest that Leucine could be used as a novel combustion fuel to produce crystalline ZnAl₂O₄ nanoparticles in their as-synthesis form.     

A metal-organic coordination polymer based on 1,2-bis(diphenylphosphino)ethane dioxide: Synthesis,crystal structure and fluorescence of [ZnI2{Ph2P(O)-CH2CH2-P(O)Ph2}]n

A zinc coordination polymer, [ZnI₂{Ph₂P(O)-CH₂CH₂-P(O)Ph₂}]_n (1), has been prepared, which features a one-dimensional concavo-convex chain with alternative ZnI₂ and 1,2-bis(diphenylphosphino)ethane dioxide (dppeO₂) moieties. The dppeO₂ ligand adopts the bridging coordination mode between two zinc atoms.