Crystal structure of 3-acetylcoumarin-o-aminobenzoylhydrazone and synthesis, spectral and thermal studies of its transition metal complexes

Transition metal [Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II)] complexes of a new Schiff base, 3-acetylcoumarin-o-aminobenzoylhydrazone were synthesized and characterized by elemental analyses, magnetic moments, conductivity measurements, spectral [Electronic, IR, H-1 and C-13 NMR, EPR] and thermal studies. The ligand crystallizes in the monoclinic system, space group P2(1)/n with a = 9.201(5), b = 16.596( 9), c = 11.517(6) angstrom, beta= 101.388(9)degrees, V = 1724.2 (17) angstrom(3) and Z = 4. Conductivity measurements indicated Mn(II) and Co(II) complexes to be 1 : 1 electrolytes whereas Ni(II), Cu(II), Zn(II) and Cd(II) complexes are non-electrolytes. Electronic spectra reveal that all the complexes possess four-coordinate geometry around the metal.

Coordination polymers and hybrid networks of different dimensionalities formed by metal sulfites

In our effort to explore the use of the sulfite ion to design hybrid and open-framework materials, we have been able to prepare, under hydrothermal conditions, zero-dimensional [Zn(C12H8N2)(SO3)]center dot 2H(2)O, I (a = 7.5737(5) angstrom, b = 10.3969(6) angstrom, c = 10.3986(6) angstrom, alpha = 64.172(1)degrees, beta = 69.395(1)degrees, gamma = 79.333(1)degrees, Z = 2, and space group P (1) over bar), one-dimensional [Zn-2(C12H8N2)(SO3)(2)(H2O)], II (a = 8.0247(3) angstrom, b = 9.4962(3) angstrom, c = 10.2740(2) A, alpha = 81.070(1)degrees, beta = 80.438(1)degrees, gamma = 75.66(5)degrees, Z = 2, and space group P (1) over bar), two-dimensional [Zn-2(C10H8N2)(SO3)(2)]center dot H2O, III (a = 16.6062(1) angstrom, b = 4.7935(1) angstrom, c = 19.2721(5) angstrom, beta = 100.674(2)degrees, Z = 4, and space group C2/c), and three-dimensional [Zn-4(C6H12N2)(SO3)(4)(H2O)(4)], IV (a = 11.0793(3) angstrom, c = 8.8246(3) angstrom, Z = 2, and space group P42nm), of which the last three are coordination polymers. A hybrid open-framework sulfite-sulfate of the composition [C2H10N2][Nd(SO3)(SO4)(H2O)](2), V (a = 9.0880(3) angstrom, b = 6.9429(2) angstrom, c = 13.0805(5) A, beta = 91.551(2)degrees, Z = 2, and space group P2(1)/c), with a layered structure containing metal-oxygen-metal bonds has also been described.

Insight into the early stages of thermal unfolding of peanut agglutinin by molecular dynamics simulations

Peanut agglutinin is a homotetrameric nonglycosylated protein. The protein has a unique open quaternary structure. Molecular dynamics simulations have been employed follow the atomistic details of its unfolding at different temperatures. The early events of the deoligomerization of the protein have been elucidated in the present study. Simulation trajectories of the monomer as well as those of the tetramer have been compared and the tetramer is found to be substantially more stable than its monomeric counterpart. The tetramer shows retention of most of its.. secondary structure but considerable loss of the tertiary structure at high temperature. e generation of a This observation impies the molten globule-like intermediate in the later stages of deoligomerization. The quaternary structure of the protein has weakened to a large extent, but none of the subunits are separated. In addition, the importance of the metal-binding to the stability of the protein structure has also been investigated. Binding of the metal ions not only enhances the local stability of the metal-ion binding loop, but also imparts a global stability to the overall structure. The dynamics of different interfaces vary significantly as probed through interface clusters. The differences are substantially enhanced at higher temperatures. The dynamics and the stability of the interfaces have been captured mainly by cluster analysis, which has provided detailed information on the thermal deoligomerization of the protein.

Nanoscale Heterostructures with Molecular-Scale Single-Crystal Metal Wires

Creating nanoscale heterostructures with molecular-scale (<2 nm) metal wires is critical for many applications and remains a challenge. Here, we report the first time synthesis of nanoscale heterostructures with single-crystal molecular-scale Au nanowires attached to different nanostructure substrates. Our method involves the formation of Au nanoparticle seeds by the reduction of rocksalt AuCl nanocubes heterogeneously nucleated on the Substrates and subsequent nanowire growth by oriented attachment of Au nanoparticles from the Solution phase. Nanoscale heterostructures fabricated by such site-specific nucleation and growth are attractive for many applications including nanoelectronic device wiring, catalysis, and sensing.

Book Review: "The Interface: IBM and the Transformation of Corporate Design, 1945-1975", John Harwood, Minneapolis: University of Minnesota Press, 2011

Within the history of twentieth-century design, there are a number of well-known objects and stories that are invoked time and time again to capture a pivotal moment or summarize a much broader historical transition. For example, Marcel Breuer’s Model B3 chair is frequently used as a stand-in for the radical investigations of form and new industrial materials occurring at the Bauhaus in the mid-1920s. Similarly, Raymond Loewy’s streamlined pencil sharpener has become historical shorthand for the emergence of modern industrial design in the 1930s. And any discussion of the development of American postwar “organic design” seems incomplete without reference to Charles and Ray Eames’s molded plywood leg splint of 1942. Such objects and narratives are dear to historians of modern design. They are tangible, photogenic subjects that slot nicely into exhibitions, historical surveys, and coffee-table best sellers...

Low-frequency resistance fluctuations in metal films under current stressing at low temperature (T<0.3Tmelting)

In this paper, we report a systematic study of low frequency 1∕fα resistance fluctuation in thin metal films (Ag on Si) at different stages of damage process when the film is subjected to high current stressing. The resistance fluctuation (noise) measurement was carried out in situ using a small ac bias that has been mixed with the dc stressing current. The experiment has been carried out as a function of temperature in the range of 150–350 K. The experiment establishes that the current stressed film, as it undergoes damage due to various migration forces, develops an additional low-frequency noise spectral power that does not have the usual 1∕f spectral shape. The magnitude of extra term has an activated temperature dependence (activation energy of ≈0.1 eV) and has a 1∕f1.5 spectral dependence. The activation energy is the same as seen from the temperature dependence of the lifetime of the film. The extra 1∕f1.5 spectral power changes the spectral shape of the noise power as the damage process progress. The extra term likely arising from diffusion starts in the early stage of the migration process during current stressing and is noticeable much before any change can be detected in simultaneous resistance measurements. The experiment carried out over a large temperature range establish a strong correlation between the evolution of the migration process in a current stressed film and the low-frequency noise component that is not a 1∕f noise.

Microscopic Frictional Response of Sodium Oleate Self-Assembled on Steel

The article peruses the frictional response of an important metal working lubricant additive, sodium oleate. Frictional force microscopy is used to track the response of molecules self-assembled on a steel substrate of 3–4 nm roughness at 0% relative humidity. The friction-normal load characteristic emerges as bell-shaped, where the peak friction and normal load at peak friction are both sensitive to substrate roughness. The frictional response at loads lower than that associated with the peak friction is path reversible while at higher loads the loading and unloading paths are different. We suggest that a new low-friction interface material is created when the normal loads are high.

'Wet N2O oxidation' process and interface state density characterization of nanoscale nitrided SiO2 for flash memory application

In this paper we first present the 'wet N2O' furnace oxidation process to grow nitrided tunnel oxides in the thickness range 6 to 8 nm on silicon at a temperature of 800 degrees C. Electrical characteristics of MOS capacitors and MOSFETs fabricated using this oxide as gate oxide have been evaluated and the superior features of this oxide are ascertained The frequency response of the interface states, before and after subjecting the MOSFET gate oxide to constant current stress, is studied using a simple analytical model developed in this work.

Self-interrupted regenerative metal cutting in turning

A new approach is used to study the global dynamics of regenerative metal cutting in turning. The cut surface is modeled using a partial differential equation (PDE) coupled, via boundary conditions, to an ordinary differential equation (ODE) modeling the dynamics of the cutting tool. This approach automatically incorporates the multiple-regenerative effects accompanying self-interrupted cutting. Taylor's 3/4 power law model for the cutting force is adopted. Lower dimensional ODE approximations are obtained for the combined tool–workpiece model using Galerkin projections, and a bifurcation diagram computed. The unstable solution branch off the subcritical Hopf bifurcation meets the stable branch involving self-interrupted dynamics in a turning point bifurcation. The tool displacement at that turning point is estimated, which helps identify cutting parameter ranges where loss of stability leads to much larger self-interrupted motions than in some other ranges. Numerical bounds are also obtained on the parameter values which guarantee global stability of steady-state cutting, i.e., parameter values for which there exist neither unstable periodic motions nor self-interrupted motions about the stable equilibrium.

Stabilization of an All-Metal Antiaromatic Molecule (Al4Li4) Using BH and C as Caps

It has been reported by Pati et al. (J. Am. Chem. Soc. 2005, 127, 3496) that coordination with a transition metal can stabilize the “antiaromatic”, all-metal compound Al4Li4. Here, we report that it can also be stabilized by capping with a main group element like C and its isoelectronic species BH. Our calculations of binding energy, nuclear independent chemical shift, energy decomposition analysis, and molecular orbital analysis support the capping-induced stability, reduction of bond length alternation, and increase of aromaticity of these BH/C-capped Al4Li4 systems. The interaction between px and py orbitals of BH/C and the HOMO and LUMO of Al4Li4 is responsible for the stabilization. Our calculations suggest that capping can introduce fluxionality at room temperature.

Unusual Hydrogenation of Fumarate Anion Followed by Metal−Carbon Bond Formation: Synthesis and Characterization of Two Metallochelates

The treatment of [M(dppf)(H2O)2](OTf)2 (dppf =1,1′-bis(diphenylphosphino)ferrocene; M = Pd, Pt) with 1 equiv of disodium fumarate in methanol medium showed an unusual hydrogenation of the ethylenic bond followed by the formation of metallochelates linking M through one of the carboxylates and the β-carbon with respect to COO−. Despite the possibility of formation of a [2 + 2] or [4 + 4] self-assembled macrocycle, the reduction of fumarate to succinate, and in particular the linking through the β-carbon, is unique since a similar treatment using disodium succinate instead of disodium fumarate yielded an expected metallochelate where both the carboxylates were coordinated to the square-planar metal.

Interlayer structure of iodide intercalated layered double hydroxides (LDHs)

The iodide-containing layered double hydroxides (LDHs) of Mg and Zn with AI crystallize by the inclusion of extensive positional disorder of I- ions in the interlayer region. I- ion given its poor charge to size ratio can neither screen effectively the positive charge nor participate in H-bonding with the metal hydroxide layers. Thereby the I- ions are not stabilized in sites close to the seat of positive charge of the metal hydroxide layers (6c), nor in sites that facilitate H-bonding (3b or 18h). On the other hand, OH- from water can do both and effectively displaces I- from the interlayer. (C) 2010 Elsevier Inc. All rights reserved.

Metal-ion-mediated tuning of duplex DNA binding by bis(2-(2-pyridyl)-1H-benzimidazole)

Studies of double-stranded-DNA binding have been performed with three isomeric bis)2-(n-pyridyl)-1H-benzimidazole)s (n = 2, 3, 4). Like the well-known Hoechst 33258, which is a bisbenzimidazole compound, these three isomers bind to the minor groove of duplex DNA. DNA binding by the three isomers was investigated in the presence of the divalent metal ions Mg2+, Co2+, Ni2+, Cu2+, and Zn2+. Ligand-DNA interactions were probed with fluorscence and circular dichroism spectroscopy. These studies revealed that the binding of the 2-pyridyl derivative to DNA is dramatically reduced in the presence of Co2+, Ni2+, and Cu2+ ions and is abolished completely at a ligand/metal-cation ratio of 1:1. Control experiments done with the isomeric 3- and 4-pyridyl derivatives showed that their binding to DNA is unaffected by the aforementioned transition-metal ions. The ability of 2-(2-pyridyl)benzimidazole changes of the ligand associated with ion chelation probably ledto such unusual binding results for the ortho isomer. The addition of ethylenediaminetetraacetic acid (EDTA) reversed the effects completely.

Metal-spinel-corundum three phase equilibria in the system Ni-Cr-Al-O at 1373 K

The tie-lines representing the inter-crystalline ion exchange equilibria between the NiCr2O4-NiAl2O4 spinet solid solution and Cr2O3-Al2O3 corundum solid solution are determined by electron microprobe andEDAX pointcountanalysis of the oxide phases equilibrated with metallic Ni at 1373 K. The component activities in the spinet solid solution are derived from the tie-lines and thermodynamic data for Cr2O3-Al2O3 solid solution available in the literature. The Gibbs energy of mixing of the spinet solid solution calculated from the experimental data is discussed in relation to the values derived from the cation distribution models which assume random mixing of cations on both tetrahedral and octahedral sites. Positive deviation from the models is observed indicating significant positive enthalpy contribution arising form the size mismatch between Al+3 and Ni+2 ions on the tetrahedral site and Al+3, Ni+2 and Cr+3 on the octahedral site. Variation of the oxygen potential for threephase equilibrium involving metallic nickel, spinet solid solution and corundum solid solution is computed as a function of composition of the solid solutions at 1373 K. The oxygen potential exhibits a minimum at aluminum cationic fraction eta(Al)/(eta(Al) + eta(Cr)) = 0.524 in the oxide solid solutions.