Electrocatalysis of Nitrate Reduction at Copper‐Nickel Alloy Electrodes in Acidic Media

The cathodic reduction of NO in 1.0 M HClO₄ is investigated by voltammetry at pure Ni and Cu electrodes, and three Cu‐Ni alloy electrodes of varying composition, all configured as rotated disks. Voltammetric data obtained using these hydrodynamic electrodes demonstrate significantly improved activity for NO reduction at Cu‐Ni alloy electrodes as compared to the pure Ni and Cu electrodes. This observation is explained on the basis of the synergistic benefit of different surface sites for adsorption of H‐atoms, generated by cathodic discharge of H⁺ at Ni‐sites, and adsorption of NO at Cu‐sites on these binary alloy electrodes. Koutecky‐Levich plots indicate that the cathodic response for NO at a Cu₇₅Ni₂₅ electrode corresponds to an 8‐electron reduction, which is consistent with production of NH₃. In comparison, the cathodic response at Cu₅₀Ni₅₀ and Cu₂₅Ni₇₅ electrodes corresponds to a 6‐electron reduction, which is consistent with production of NH₂OH. Flow injection data obtained using Cu₅₀Ni₅₀ and Cu₂₅Ni₇₅ electrodes with 100‐μL injections exhibit detection limits for NO of ca. 0.95 μM (ca. 95 pmol) and 0.60 μM (ca. 60 pmol), respectively.     

One-step synthesis of porous PtNiCu trimetallic nanoalloy with enhanced electrocatalytic performance toward methanol oxidation

Pt-based alloy nanoporous structures have attracted a lot of attention because of their high activity and stability toward alcohol oxidation reactions. Especially, Pt alloying with Earth-abundant metal can lower the cost of catalyst. Here, we introduce a one-pot approach to synthesize bimetallic PtCu and Ni-doped PtCu nanoalloy with porous structure. The as-synthesized Ni-doped Pt₆₀Ni₃Cu₃₇ nanoalloys exhibit excellent electrocatalytic properties toward methanol oxidation in acidic medium. The mass activity of the as-synthesized Pt₆₀Ni₃Cu₃₇ nanoalloys is 3.6 times and 5.3 times that of Pt₅₅Cu₄₅ nanoalloys and commercial Pt black for methanol oxidation in 0.2?M methanol solution. Besides, the stability of the as-synthesized Pt₆₀Ni₃Cu₃₇ nanoalloys was much better than Pt₅₅Cu₄₅ nanoalloys and commercial Pt black. After 3600?s chronoamperometry test, the remaining values of the Pt₆₀Ni₃Cu₃₇ nanoalloys are 3.7 times and 11.0 times that of Pt₅₅Cu₄₅ nanoalloys and commercial Pt black. And it is the first time to report that small amount of Ni dopants can boost the activity and stability of PtNiCu alloys toward methanol oxidation.     

Skeletal Ni Catalysts Prepared from Amorphous Ni–Zr Alloys: Enhanced Catalytic Performance for Hydrogen Generation from Ammonia Borane

Skeletal Ni catalysts were prepared from Ni–Zr alloys, which possess different chemical composition and atomic arrangements, by a combination of thermal treatment and treatment with aqueous HF. Hydrogen generation from ammonia borane over the skeletal Ni catalysts proceeded efficiently, whereas the amorphous Ni–Zr alloy was inactive. Skeletal Ni prepared from amorphous Ni₃₀Zr₇₀ alloy had a higher catalytic activity than that prepared from amorphous Ni₄₀Zr₆₀ and Ni₅₀Zr₅₀ alloys. The atomic arrangement of the Ni–Zr alloy also strongly affected the surface structure and catalytic activities. Thermal treatment of the amorphous Ni–Zr alloys at a temperature slightly lower than the crystallization temperature led to an increase of the number of surface‐exposed Ni atoms and an enhancement of the catalytic activities for hydrogen generation from ammonia borane. The skeletal Ni catalysts also showed excellent durability and recyclability.     

Cu/活性炭催化剂：水合肼还原制备及催化甲醇氧化羰基化

以活性炭为载体,水合肼为还原剂制备了负载型Cu/活性炭催化剂,考察了水合肼/硝酸铜物质的量的比对催化甲醇气相氧化羰基化性能的影响,并采用XRD、XPS、H2-TPR和SEM等手段对催化剂进行了表征。结果表明,不加入还原剂水合肼时,催化剂中仅有CuO;随着水合肼/硝酸铜物质的量的比的增加,二价铜逐步被还原为Cu2O和/或单质Cu0,未被还原的Cu(OH)2在催化剂干燥过程中分解形成分散态CuO存在于催化剂表面。当水合肼/硝酸铜物质的量的比为0.75时,催化剂的催化性能最好,碳酸二甲酯的时空收率为120.62 mg.(g.h)-1,选择性为74.51%,甲醇转化率达到3.88%。在93 h反应时间内,催化剂都保持了较高的反应活性和选择性。此时铜物种以Cu2O和分散态CuO为主,Cu2O是主要的活性物种。     

Furfural Hydrogenation on Nickel‐promoted Cu‐containing Catalysts Prepared from Hydrotalcite‐Like Precursors

The nickel‐promoted Cu‐containing catalysts (Cu_xNi_y‐MgAlO) for furfural (FFR) hydrogenation were prepared from the hydrotalcite‐like precursors, and characterized by X‐ray powder diffraction, inductively‐coupled plasma atomic emission spectroscopy, N₂ adsorption‐desorption, UV‐Vis diffuse reflectance spectra and temperature‐programmed reduction with H₂ in the present work. The obtained catalysts were observed to exhibit a better catalytic property than the corresponding Cu‐MgAlO or Ni‐MgAlO samples in FFR hydrogenation, and the CuNi‐MgAlO catalyst with the actual Cu and Ni loadings of 12.5 wt% and 4.5 wt%, respectively, could give the highest FFR conversion (93.2%) and furfuryl alcohol selectivity (89.2%). At the same time, Cu⁰ species from the reduction of Cu²⁺ ions in spinel phases were deduced to be more active for FFR hydrogenation.     

Production of hydrogen by oxidative steam reforming of methanol over Cu/SiO2 catalysts

Selective production of hydrogen by oxidative steam reforming of methanol (OSRM) was studied over Cu/SiO₂ catalyst using fixed bed flow reactor. Textural and structural properties of the catalyst were analyzed by various instrumental methods. TPR analysis illustrates that the reduction temperature peak was observed between 510?K and 532?K at various copper loadings and calcination temperatures and the peaks shifted to higher temperature with increasing copper loading and calcination temperature. The XRD and XPS analysis demonstrates that the copper existed in different oxidation states at different conditions: Cu₂O, Cu⁰, CuO and Cu(OH)₂ in uncalcined sample; CuO in calcined sample: Cu₂O and metallic Cu after reduction at 600?K and Cu⁰ and CuO after catalytic test. TEM analysis reveals that at various copper loadings, the copper particle size is in the range between 3.0?nm and 3.8?nm. The Cu particle size after catalytic test increased from 3.6 to 4.8?nm, which is due to the formation of oxides of copper as evidenced from XRD and XPS analysis. The catalytic performance at various Cu loadings shows that with increasing Cu loading from 4.7 to 17.3?wt%, the activity increases and thereafter it decreases. Effect of calcination shows that the sample calcined at 673?K exhibited high activity. The O₂/CH₃OH and H₂O/CH₃OH molar ratios play important role in reaction rate and product distribution. The optimum molar ratios of O₂/CH₃OH and H₂O/CH₃OH are 0.25 and 0.1, respectively. When the reaction temperature varied from 473 to 548?K, the methanol conversion and H₂ production rate are in the range of 21.9–97.5% and 1.2–300.9?mmol?kg^?1?s^?1, respectively. The CO selectivity is negligible at these temperatures. Under the optimum conditions (17.3?wt%, Cu/SiO₂; calcination temperature 673?K; 0.25 O₂/CH₃OH molar ratio, 0.5 H₂O/CH₃OH molar ratio and reaction temperature 548?K), the maximum hydrogen yield obtained was 2.45?mol of hydrogen per mole of methanol. The time on stream stability test showed that the Cu/SiO₂ catalyst is quite stable for 48?h.     

Synthese,Strukturen und X‐/Q‐Band‐EPR‐Untersuchungen von N,N‐Diethyl‐N′‐3,5‐di(trifluormethyl)benzoylthioureato‐Komplexen des CuII,NiII und PdII sowie EPR‐spektroskopische Charakterisierung eines CuII‐CuII‐Dimers

The synthesis and the structures of (i) the ligand N,N‐Diethyl‐N′‐3,5‐di(trifluoromethyl)benzoylthiourea HEt₂dtfmbtu and (ii) the Ni^II and Pd^II complexes of HEt₂dtfmbtu are reported. The ligand coordinates bidendate forming bis chelates. The Ni^II and the Pd^II complexes are isostructural. The also prepared Cu^II complex could not be characterized by X‐ray analysis. However, the preparation of diamagnetically diluted powders Cu/Ni(Et₂dtfmbtu)₂ and Cu/Pd(Et₂dtfmbtu)₂ suitable for EPR studies was successful. The EPR spectra of the Cu/Ni and Cu/Pd systems show noticeable differences for the symmetry of the CuS₂O₂ unit in both complexes: the Cu/Pd system is characterized by axially‐symmetric g< and A ^cu tensors; for the Cu/Ni system g and A ^Cu have rhombic symmetry. EPR studies on frozen solutions of the Cu^II complex show the presence of a Cu^II‐Cu^II dimer which is the first observed for Cu^II acylthioureato complexes up to now. The parameters of the fine structure tensor were used for the estimation of the Cu^II‐Cu^II distance.     

Green synthesis of Ni‐Cu‐Zn ferrite nanoparticles using tragacanth gum and their use as an efficient catalyst for the synthesis of polyhydroquinoline derivatives

Ni_0.35Cu_0.25Zn_0.4Fe₂O₄ MNPs were synthesized using tragacanth gum as biotemplate and Metals nitrate as the metal source by the sol–gel method. The sample was characterized by powder X‐ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), vibrating sample magnetometer (VSM), scanning electron microscopy (SEM) and energy dispersive X‐ray analysis (EDX). The nanoparticles exhibit ferromagnetic behaviour at room temperature, with a saturation magnetization of 52.76 emu/g and a coercivity of 80.14 Oe. Thereupon, Ni‐Cu‐Zn ferrite nanoparticles as an efficient catalyst was used for the synthesis of polyhydroquinoline derivatives via multi‐component reactions under microwave irradiation. Simple work‐up, mild reaction conditions, short reaction times, use of an economically convenient catalyst, and excellent product yields are the advantageous features of this method. The catalyst could easily be recycled and reused few times without noticeable decrease in catalytic activity.     

Der chemische Transport von Ni3Ge,Ni5Ge3, Ni(Ge)-Mischkristall,CoSn, Co3Sn2, Cu41Sn11 (δ-Phase), Cu10Sn3 (ζ-Phase) und Cu(Sn)-Mischkristall

Chemical Vapour Transport of Intermetallic Systems. 7. Chemical Transport of Ni₃Ge, Ni₅Ge₃, Ni(Ge)-mixed Crystal, CoSn, Co₃Sn₂, Cu₄₁Sn₁₁ (δ-phase), Cu₁₀Sn₃ (ζ-phase), and Cu(Sn)-mixed Crystals By means of GaI₃ as transport agent some intermetallics in the Ni/Ge- and Co/Sn-system can be prepared by CVT-methods. Using Iodine Cu–Sn-compounds can be deposited in a similiar way.     

In situ green synthesis of Cu‐Ni bimetallic nanoparticles supported on reduced graphene oxide as an effective and recyclable catalyst for the synthesis of N‐benzyl‐N‐aryl‐5‐amino‐1H‐tetrazoles

In the present work, for the first time we have designed a novel approach for the synthesis of N‐benzyl‐N‐aryl‐5‐amino‐1H‐tetrazoles using reduced graphene oxide (rGO) decorated with Cu‐Ni bimetallic nanoparticles (NPs). In situ synthesis of Cu/Ni/rGO nanocomposite was performed by a cost efficient, surfactant‐free and environmentally benign method using Crataegus azarolus var. aronia L. leaf extract as a stabilizing and reducing agent. Phytochemicals present in the extract can be used to reduce Cu²⁺ and Ni²⁺ ions and GO to Cu NPs, Ni NPs and rGO, respectively. Analyses by means of FT‐IR, UV–Vis, EDS, TEM, FESEM, XRD and elemental mapping confirmed the Cu/Ni/rGO formation and also FT‐IR, NMR, and mass spectroscopy as well as elemental analysis were used to characterize the tetrazoles. The Cu/Ni/rGO nanocomposite showed the superior catalytic activity for the synthesis of N‐benzyl‐N‐aryl‐5‐amino‐1H‐tetrazoles within a short reaction time and high yields. Furthermore, this protocol eliminates the need to handle HN₃.     

新型的钛基Ni-Sn/Ti电极的制备及对甲醇氧化反应的电催化活性

利用电热法,一步制备出新型的钛基Ni-Sn/Ti电极(Ni8Sn/Ti, Ni7Sn3/Ti 和 Ni/Ti)。扫描电镜（SEM）图像表明,催化剂以片状的纳米颗粒形式沉积于钛基体上。利用电化学伏安技术、电位阶跃法和电化学交流阻抗谱（EIS）,研究了这些电极在1mol.L�1NaOH溶液中对甲醇氧化反应的电催化活性。研究表明,与Ni7Sn3/Ti,Ni/Ti以及多晶镍电极相比,Ni8Sn/Ti电极对甲醇氧化反应表现出更高的阳极氧化电流和更低的起始电位。EIS分析表明,在本文所考察的阳极电位和甲醇浓度下,Ni8Sn/Ti电极对甲醇氧化反应显示出极低的电荷传递电阻。结果表明,这种新型的钛基Ni8Sn/Ti电极对甲醇氧化反应具有极高的电催化活性。     

Catalytic activity of nickel(II), copper(II) and oxovanadium(II)‐dihydroindolone complexes towards homogeneous oxidation reactions

Three novel paramagnetic metal complexes (MH₂ID) of Ni²⁺, Cu²⁺ and VO²⁺ ions with 3‐hydroxy‐3,3’‐biindoline‐2,2’‐dione (dihydroindolone, H₄ID) were synthesized and characterized by different spectroscopic methods. The ligand (H₄ID) was synthesized via homocoupling reaction of isatin in presence of phenylalanine in methanol. Complexation of low valent Ni²⁺, Cu²⁺ ions and high valent VO²⁺ ions with H₄ID carried out in 1: 2 molar ratios. A comparison in the catalytic potential of paramagnetic complexes of low and high valent metal ion was explored in the oxidation processes of cis‐cyclooctene, benzyl alcohol and thiophene by an aqueous H₂O₂, as a green terminal oxidant, in the presence and absence of acetonitrile, as an organic solvent, at 85 °C. NiH₂ID, CuH₂ID and VOH₂ID show good catalytic activity, i.e. good chemo‐ and regioselectivity. VOH₂ID has the highest catalytic potential compared to both Ni²⁺‐ and Cu²⁺‐species in the same homogenous aerobic atmosphere. Catalytic oxidation of other alkenes and alcohols was also studied using NiH₂ID, CuH₂ID or VOH₂ID as a pre‐catalyst by an aqueous H₂O₂. A mechanistic pathway for those oxidation processes was proposed.     

Synthesis and characterization of graphene oxide‐based hybrid ligand and its metal complexes: Highly efficient sensor and catalytic properties

A new graphene oxide‐based hybrid material (HL) and its Co(II), Cu(II) and Ni(II) metal complexes were prepared. Firstly, graphene oxide and (3‐aminopropyl)trimethoxysilane were reacted to give graphene oxide–3‐(aminopropyl)trimethoxysilane (GO‐APTMS) hybrid material. After that, hybrid material HL was synthesized from the reaction of GO‐APTMS and 2,6‐diformyl‐4‐methylphenol. Finally, Co(II), Cu(II) and Ni(II) complexes of HL were obtained. All the materials were characterized using various techniques. The chemosensor properties of HL were investigated against Na⁺, K⁺, Cd²⁺, Co²⁺, Cu²⁺, Hg²⁺, Ni²⁺, Zn²⁺, Al³⁺, Cr³⁺, Fe³⁺ and Mn³⁺ ions and it was found that HL has selective chemosensing to Fe³⁺ ion. All the graphene oxide‐supported complexes were used as heterogeneous catalysts in the oxidation of 2‐methylnaphthalene (2MN) to 2‐methyl‐1,4‐naphthoquinone (vitamin K₃, menadione) in the presence of hydrogen peroxide, acetic acid and sulfuric acid. The Cu(II) complex showed good catalytic properties compared to the literature. The selectivity of 2MN to vitamin K₃ was 60.23% with 99.75% conversion using the Cu(II) complex.     

In Situ Growth of Hierarchical Ni-Mn-O Solid Solution on a Flexible and Porous Ni Electrode for High-Performance All-Solid-State Asymmetric Supercapacitors

To endow all-solid-state asymmetric supercapacitors with high energy density, cycling stability, and flexibility, we design a binder-free supercapacitor electrode by in situ growth of well-distributed broccoli-like Ni_0.75Mn_0.25O/C solid solution arrays on a flexible and three-dimensional Ni current collector (3D-Ni). The electrode consists of a bottom layer of compressed but still porous Ni foam with excellent flexibility and high electrical conductivity, an intermediate layer of interconnected Ni nanoparticles providing a large specific surface area for loading of active substances, and a top layer of vertically aligned mesoporous nanosheets of a Ni_0.75Mn_0.25O/C solid solution. The resultant 3D-Ni/Ni_0.75Mn_0.25O/C cathode exhibits a specific capacitance of 1657.6 mF cm⁻² at 1 mA cm⁻² and shows no degradation of the capacitance after 10 000 cycles at 3 mA cm⁻². The assembled 3D-Ni/Ni_0.75Mn_0.25O/C//activated carbon asymmetric supercapacitor has a high specific capacitance of 797.7 mF cm⁻² at 2 mA cm⁻² and an excellent cycling stability with 85.3 % of capacitance retention after 10 000 cycles at a current density of 3 mA cm⁻². The energy density and power density of the asymmetric supercapacitor are up to 6.6 mW h cm⁻³ and 40.8 mW cm⁻³, respectively, indicating a fairly promising future of the flexible 3D-Ni/Ni_0.75Mn_0.25O/C electrode for efficient energy storage applications.     

Supported Pd–Cu Bimetallic Nanoparticles That Have High Activity for the Electrochemical Oxidation of Methanol

Monodisperse bimetallic Pd–Cu nanoparticles with controllable size and composition were synthesized by a one‐step multiphase ethylene glycol (EG) method. Adjusting the stoichiometric ratio of the Pd and Cu precursors afforded nanoparticles with different compositions, such as Pd₈₅–Cu₁₅, Pd₅₆–Cu₄₄, and Pd₃₉–Cu₆₁. The nanoparticles were separated from the solution mixture by extraction with non‐polar solvents, such as n‐hexane. Monodisperse bimetallic Pd–Cu nanoparticles with narrow size‐distribution were obtained without the need for a size‐selection process. Capping ligands that were bound to the surface of the particles were removed through heat treatment when the as‐prepared nanoparticles were loaded onto a Vulcan XC‐72 carbon support. Supported bimetallic Pd–Cu nanoparticles showed enhanced electrocatalytic activity towards methanol oxidation compared with supported Pd nanoparticles that were fabricated according to the same EG method. For a bimetallic Pd–Cu catalyst that contained 15 % Cu, the activity was even comparable to the state‐of‐the‐art commercially available Pt/C catalysts. A STEM‐HAADF study indicated that the formation of random solid‐solution alloy structures in the bimetallic Pd₈₅–Cu₁₅/C catalysts played a key role in improving the electrochemical activity.     

A Highly Stable Copper‐Based Catalyst for Clarifying the Catalytic Roles of Cu0 and Cu+ Species in Methanol Dehydrogenation

Identification of the active copper species, and further illustration of the catalytic mechanism of Cu‐based catalysts is still a challenge because of the mobility and evolution of Cu⁰ and Cu⁺ species in the reaction process. Thus, an unprecedentedly stable Cu‐based catalyst was prepared by uniformly embedding Cu nanoparticles in a mesoporous silica shell allowing clarification of the catalytic roles of Cu⁰ and Cu⁺ in the dehydrogenation of methanol to methyl formate by combining isotope‐labeling experiment, in situ spectroscopy, and DFT calculations. It is shown that Cu⁰ sites promote the cleavage of the O?H bond in methanol and of the C?H bond in the reaction intermediates CH₃O and H₂COOCH₃ which is formed from CH₃O and HCHO, whereas Cu⁺ sites cause rapid decomposition of formaldehyde generated on the Cu⁰ sites into CO and H₂.     

The structural, magnetic, hydrogenation and electrode properties of REMg2Cu9?xNix alloys (RE=La, Pr,Tb)

The LaMg₂Cu₉, PrMg₂Cu₉, LaMg₂Cu₄Ni₅, PrMg₂Cu₄Ni₅ and TbMg₂Cu₆Ni₃ alloys were prepared for the investigations of crystal structure, magnetic and hydrogen storage properties. The magnetic properties of several REMg₂Cu_9−xNi_x compounds have been studied up to 9 T and from 2 to 300 K. Tb compounds show a ferrimagnetic (with Ni) or antiferromagnetic (without Ni) behaviour, which can be attributed to the Tb magnetic structure. At high temperature a paramagnetic Curie Weiss behaviour is observed and the effective moment corresponds to that of Tb. A magnetic contribution of Pr moment is observed in both Pr compounds, with larger magnetization for PrMg₂Cu₄Ni₅ and a transition at 3 K. The hydrogen absorption occurs at 95 bar for LaMg₂Cu₉ (3 H f.u.⁻¹) and above 2 bars for LaMg₂Cu₄Ni₅ (1.6 H f.u.⁻¹). The effect of Cu-Ni substitution on the electrochemical properties of LaMg₂M₉ ternary alloys was investigated leading to maximum discharge capacity of 250–310 mAh g⁻¹.      

The preparation and characterization of some new nickel(II), copper(II), zinc(II) and cadmium(II) complexes of the pyrrole-2-carboxaldehyde Schiff bases ofS-alkyl esters of dithiocarbazic acid

Summary New complexes of general formulae [Ni(HL)₂], [ML]·H₂O and [Cu(HL)X] (H₂L = pyrrole-2-aldehyde Schiff bases ofS-methyl- andS-benzyldithiocarbazates; X = Cl or Br; M = Ni^II, Cu^II, Zn^II or Cd^II) were prepared and characterized by a variety of physicochemical techniques. The Schiff bases coordinate as NS bidentate chelating agents in [Ni(HL)₂] and [Cu(HL)X], and as tridentate NNS chelates in [ML] (M = Ni^II, Cu^II, Zn^II or Cd^II). Both the [Ni(HL)₂] and [NiL] complexes are diamagnetic and square-planar. Based on magnetic and spectroscopic evidence, thiolate sulphur-bridged dimeric square-planar structures are assigned to the [Cu(HL)X] and [ML] (M = Ni^II or Cu^II) complexes. The complexes ML (M = Zn^II or Cd^II) are polymeric and octahedral.     

Heterometallic Mixed‐Valence Copper(I,II) Cyanides that were Tuned by Using the Chelate Effect: Discovery of Famous Cairo Pentagonal Tiling and Unprecedented (3,4)‐Connected {83}2{86} Topological 3D Net

By using environmentally friendly [Ni(CN)₄]^2? as a cyanide source, three new heterometallic cyano‐bridged mixed‐valence Cu^I/Cu^II coordination polymers with three different electronic configurations (d⁸–d¹⁰), that is, [Cu₂Ni(CN)₅(H₂O)₃] ( 1 ), [Cu₂Ni(CN)₅(pn)H₂O] ( 2 ), and [Cu₃Ni(CN)₆(pn)₂] ( 3 , pn=1,2‐propane diamine) have been synthesized by gradually increasing the amount of pn. Compound 1 , which was hydrothermally synthesized in the absence of pn ligand, exhibits the famous 2D Cairo pentagonal tiling, in which the Cu^I, Cu^II, and Ni^II atoms act as trigonal, T‐shaped, and square‐planar nodes, respectively. Notably, there are three water molecules located at the meridianal positions of the octahedrally coordinated Cu^II atom in compound 1 . A similar reaction, except for the addition of a small amount of pn, generated a similar Cairo pentagonal tiling layer in which two of the water molecules that were located at the meridianal positions of the octahedrally coordinated Cu^II atom were replaced by a chelating pn group. Another similar hydrothermal reaction, with the addition of a larger amount of pn, yielded compound 3 , which showed a related two‐fold‐interpenetrated (3,4)‐connected 3D framework with an unprecedented {8³}₂{8⁶} topology in which the Cu^II atom was chelated by two pn groups. These structural changes between compounds 1 , 2 , 3 can be explained by the chelating effect of the pn group. The replacement of two meridianally coordinated water molecules on the octahedral Cu^II atom in compound 1 by a pn group gives compound 2 , which shows similar Cairo tiling, and a further increase in the amount of pn results in the formation of the [Cu(NC)₂(pn)₂] unit and the two‐fold‐interpenetrated 3D framework of compound 3 . The mixed‐valence properties of compounds 1 , 2 , and 3 were confirmed by variable‐temperature magnetic‐susceptibility measurements.     

Theoretical investigation of half‐metallicity in Co/Ni substituted AlN

Results of Co and Ni substituted AlN in the zinc blende phase are presented. For spin up states, the hybridized N‐2p and Co/Ni‐3d states form the valance bands with a bandgap around the Fermi level for both materials, while in the case of the spin down states, the hybridized states cross the Fermi level and hence show metallic nature. It is found that, Al_0.75Co_0.25N and Al_0.75Ni_0.25N are ferromagnetic materials with magnetic moments of 4 μ_B and 3 μ_B, respectively. The integer magnetic moments and the full spin polarization at the Fermi level make these compounds half‐metallic semiconductors. Furthermore it is also found that the interaction with the N‐2p state splits the 5‐fold degenerate Co/Ni‐3d states into t_2g and e_g states. The t_2g states are located at higher energies than the e_g states caused by the tetrahedral symmetry of these compounds. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011