Oxidative behaviour and relative reactivities of α,β-unsaturated compounds towards bis(dihydrogentellurato)cuprate(III) and -argentate(III) in alkaline medium

The kinetics of oxidation of three alpha beta-unsaturated compounds, CH2CHX (X=CN, CONH2 and CO2-) by bis(dihydrogentellurato)metallate(III) ions ([MIII-(H2TeO6)2]5-, M=Cu or Ag) have been studied in an alkaline medium. The reactions take place according to the rate expression: The k3 values are 2.42*10-2, 1.67*10-2 and 1.10*10-2mol6dm-2s-1 for oxidations of the respective substrate by the copper(III) complex and 1.49*10-2, 1.07*10-2 and 0.80*10-2mol6dm-2s-1, respectively, in the oxidations by silver(III), all at 303K. [CuIII(H2TeO6)2]5- reacts faster than the corresponding reactions with [AgIII(H2TeO6)2]5-. The oxidation rates follow the order: CN CONH2CO2-. The oxidations of the substrates by [CuIII(H2TeO6)2]5- take place by an outer-sphere mechanism, unlike [AgIII-(H2TeO6)2]5-, which reacts by an inner-sphere mechanism. The substrates are oxidized to diols under kinetic control and a tentative reaction mechanism leading to the formation of oxidation products is suggested. The activation parameters of the reactions have been evaluated. This revised version was published online in June 2006 with corrections to the Cover Date.     

Field-Induced SMM Behaviour of Tetranuclear Coordination Clusters with a Cubane [Ni4O4] Core

Two tetranuclear Ni(II) complexes: [Ni₄(HL¹)₄] ⋅ H₂O ( 1 ) and [Ni₄(HL²)₄] ⋅ 1.5 dmf ( 2 ) where dmf=dimethylformamide, H₃L¹=4-(tert-butyl)-2-(((2-hydroxy-5-nitrophenyl)imino)methyl)-6-(hydroxymethyl)phenol and H₃L²=4-(tert-butyl)-2-(hydroxymethyl)-6-(((2-hydroxyphenyl)-imino)methyl)phenol, have been prepared and characterized by single crystal X-Ray diffraction, elemental analysis and FT-IR spectroscopy. The solid-state structures reveal the formation of highly symmetric and asymmetric [Ni₄O₄] cubane cores in complexes 1 and 2 , respectively. Extensive magnetic studies show that both complexes present ferromagnetic exchange interactions between the Ni(II) ions within the cubane core with g=2.113(3), J₁=−7.89(8) cm⁻¹, J₂=13.3(1) cm⁻¹ and |D|=11.3(4) cm⁻¹ (for 1 ) and g=2.206(4), J₁=1.0(1) cm⁻¹, J₂=7.8(1) cm⁻¹ and |D|=8.7(2) cm⁻¹ (for 2 ). The large anisotropy, high ground spin state (arising from the ferromagnetic coupling) and the good isolation of the clusters provided by the Schiff base ligands, give rise to the first examples of field-induced single-molecule magnets (FI−SMM) in Ni₄O₄ clusters and to the highest energy barrier reported to date in a Ni₄O₄ cluster.     

Unpolarized structure functions and the parton distributions for nucleon in an independent quark model

Considering the nucleon as consisting entirely of its valence quarks confined independently in a scalar-vector harmonic potential; unpolarized structure functions F ₁(x, μ ²) and F ₂(x, μ ²) are derived in the Bjorken limit under certain simplifying assumptions; from which valence quark distribution functions u _v(x, μ ²) and d _v(x, μ ²) are appropriately extracted satisfying the normalization constraints. QCD-evolution of these input distributions from a model scale of μ ²=0.07 GeV² to a higher Q ² scale of Q ₀ ² =15 GeV² yields xu _v(x, Q ₀ ² ) and xd _v(x, Q ₀ ² ) in good agreement with experimental data. The gluon and sea-quark distributions such as G(x, Q ₀ ² ) and q _s(x, Q ₀ ² ) are dynamically generated with a reasonable qualitative agreement with the available data; using the leading order renormalization group equations with appropriate valence-quark distributions as the input.     

Development of Divide‐and‐Conquer Density‐Functional Tight‐Binding Method for Theoretical Research on Li‐Ion Battery

The density‐functional tight‐binding (DFTB) method is one of the useful quantum chemical methods, which provides a good balance between accuracy and computational efficiency. In this account, we reviewed the basis of the DFTB method, the linear‐scaling divide‐and‐conquer (DC) technique, as well as the parameterization process. We also provide some refinement, modifications, and extension of the existing parameters that can be applicable for lithium‐ion battery systems. The diffusion constants of common electrolyte molecules and LiTFSA salt in solution have been estimated using DC‐DFTB molecular dynamics simulation with our new parameters. The resulting diffusion constants have good agreement to the experimental diffusion constants.     

Two mononuclear cobalt(III) complexes exhibiting phenoxazinone synthase activity

Two mononuclear cobalt(III) complexes, namely [LCo(tmtp)(H₂O)]ClO₄?MeOH ( 1 ) (tmtp = tri(m‐tolyl)phosphine) and [LCo(PPh₃)(H₂O)]PF₆ ( 2 ), have been prepared from a polydentate ligand, N,N′‐bis(3‐methoxysalicylidehydene)cyclohexane‐1,2‐diamine ( H ₂ L ). Standard analytical techniques such as elemental analysis and UV–visible and Fourier transform infrared spectroscopies were used to characterize both complexes. The solid‐state molecular structures of both complexes were confirmed from single‐crystal X‐ray diffraction analysis. Structural analyses show that the Co(III) ion occupies the centre of a distorted octahedron in a complex cation: [LCo(tmtp)(H₂O)]⁺ and [LCo(PPh₃)(H₂O)]⁺ for 1 and 2 , respectively. Phenoxazinone synthase activities of both complexes were screened. Kinetic studies and other experimental observations reveal that the reaction follows rate saturation kinetics and proceeds through the formation of a catalyst (complex)–substrate adduct. The turnover number (K_cat) of complex 2 is 54.07 h^?1, exhibiting better catalytic activity compared to 1 (K_cat = 45.11 h^?1).     

A three‐dimensional (3D) manganese (II) coordination polymer: Synthesis,structure and catalytic activities

A new Mn (II)‐containing coordination polymer, [Mn₆(Ipa)₆(ad)?6H₂O] ( 1 ; Ipa = isophthalate ligand; ad = adenine), was synthesized by reacting hydrated manganese nitrate with isophthalic acid and adenine under solvothermal reaction conditions. Polymer 1 was characterized using single‐crystal X‐ray diffraction analysis and other techniques such as Fourier transform infrared spectroscopy, elemental analyses and powder X‐ray diffraction. The solid‐state structure of 1 confirmed the formation of a three‐dimensional framework structure based on Mn₆ secondary building units. Phase purity of bulk 1 and its thermal stability were investigated. Polymer 1 was evaluated for its performance as a heterogeneous catalyst for the Henry (nitroaldol) reaction of nitromethane with several aldehydes. The recyclability of 1 and heterogeneity of the reaction were also explored. A plausible mechanism for such reaction is proposed. To the best of our knowledge, polymer 1 represents the first example of a Mn (II)‐ and adenine‐containing coordination polymer as well as the first example of a Mn (II)‐containing coordination polymer that has been employed for the Henry reaction.     

Challenges and prospects of metal sulfide materials for supercapacitors

Worldwide, the research on advanced materials for energy storage devices has drawn greater attention. Numerous works on different energy storage materials has been reported and still continuing. Among the energy storage devices, electrochemical supercapacitors (ESs) are one of the most investigated topics. The globalization and increasing demand of smart and flexible devices has forced the current research to develop low-cost, high-energy density and stable ESs. In this regard, metal sulfides (MSs)–based materials have been envisioned for ESs applications owing to their unique and promising properties. Recently, several research articles have been published on MSs-based electrodes for ESs with enhanced performances. This review presents a brief survey on such recent developments towards synthesis of MSs and their use as an efficient electrode material in ESs. The challenges and future aspect involved with MSs to develop and establish it as a promising energy storage material are also discussed.