Copper(II) complexes of symmetrical and unsymmetrical tetradentate Schiff base ligands incorporating 1-benzoylacetone: Synthesis,crystal structures and electrochemical behavior

Three new copper(II) complexes [CuL¹]₂(ClO₄)₂ (1), [CuL²]ClO₄ (2) and [CuL³] (3) with three Schiff base ligands [HL¹ = 1-phenyl-3-{3-[(pyridin-2-ylmethylene)-amino]-propylimino}-butan-1-one, HL² = 1-phenyl-3-[3-(1-pyridin-2-yl-ethylideneamino)-propylimino]-butan-1-one and H₂L³ = 3-[3-(1-methyl-3-oxo-3-phenyl-propylideneamino)-propylimino]-1-phenyl-butan-1-one] have been synthesized and structurally characterized by X-ray crystallography. The mono-negative tetradentate asymmetric Schiff base ligands (L¹)⁻ and (L²)⁻ are chelated in complexes 1 and 2 to form square planar copper(II) complexes. In complex 1, the two units are associated weakly through ketonic oxygen of benzoylacetone fragment to form the dimeric entity. The square planar geometry of complex 3 is unusually distorted towards tetrahedral one. All three complexes exhibit reversible cyclic voltammetric responses in acetonitrile solution corresponding to the Cu^II/Cu^I redox process. The E_1/2 (−0.47 V versus SCE) of 3 shows significant anodic shift due to the tetrahedral distortion around Cu(II) compare to that of 1 and 2 (−0.82 and −0.87 V versus SCE, respectively).     

[Cu18H3(S-Adm)12(PPh3)4Cl2]: fusion of Platonic and Johnson solids through a Cu(0) center and its photophysical properties

Structural elucidation of atom-precise thiolate-protected copper nanoclusters (Cu NCs) containing Cu(0) is quite challenging. Here, we report a new adamantane-thiol-protected NC, [Cu₁₈H₃(S-Adm)₁₂(PPh₃)₄Cl₂] (Cu₁₈), which represents the first observation of a rare mononuclear Cu(0)-containing Cu₁₀H₃Cl₂ core that is constructed via kernel fusion through vertex sharing of the Platonic-solid- and Johnson-solid-geometry-like kernels and hydride-bridging. The unique core is surrounded by a Cu₈S₁₂P₄ metal–ligand motif shell and adopts a butterfly-like structure. In comparison to its closest structural analogue, the predominant effect of the principal Cu atom vacancy-induced structural rearrangement is evidenced. The occupied orbitals of this NC have a major d-orbital contribution to the distorted Cu₆ octahedral kernel, whereas unoccupied orbitals owe a contribution to the distorted Cu₅ square-pyramidal kernel. Thus, the charge transfer phenomenon is uniquely instigated between the two fused kernels through Cu(d) → Cu(d) transition via the Cu(0) center. This NC exhibits violet emission due to kernel-dominated relaxation at room temperature, which is further enhanced by confining the surface protecting ligands through recognition-site-specific host–guest supramolecular adduct formation by β-cyclodextrin. The unique electronic structure of this NC further facilitates its application toward photocurrent generation. Thus, this study offers a unique strategy for the controllable synthesis of a Cu(0)-containing Cu NC, which enables atomic-level insights into their optoelectronic properties.

An example of a butterfly-like [Cu₁₈H₃(S-Adm)₁₂(PPh₃)₄Cl₂] cluster with vertex-sharing kernels through a Cu(0) center. Combined experimental and theoretical results correlate its photophysical properties with its unique structural architecture.     

Local maximum principle satisfying high‐order non‐oscillatory schemes

The main contribution of this work is to classify the solution region including data extrema for which high‐order non‐oscillatory approximation can be achieved. It is performed in the framework of local maximum principle (LMP) and non‐conservative formulation. The representative uniformly second‐order accurate schemes are converted in to their non‐conservative form using the ratio of consecutive gradients. Using the local maximum principle, these non‐conservative schemes are analyzed for their non‐linear LMP/total variation diminishing stability bounds which classify the solution region where high‐order accuracy can be achieved. Based on the bounds, second‐order accurate hybrid numerical schemes are constructed using a shock detector. The presented numerical results show that these hybrid schemes preserve high accuracy at non‐sonic extrema without exhibiting any induced local oscillations or clipping error. Copyright © 2015 John Wiley & Sons, Ltd.     

Sequence‐Dependent Duplex Stabilization upon Formation of a Metal‐Mediated Base Pair

An artificial nucleoside surrogate with 1H‐imidazo[4,5‐f][1,10]phenanthroline ( P ) acting as an aglycone has been introduced into DNA oligonucleotide duplexes. This nucleoside surrogate can act as a bidentate ligand, and so is useful in the context of metal‐mediated base pairs. Several duplexes involving a hetero base pair with an imidazole nucleoside have been investigated. The stability of DNA duplexes incorporating the respective Ag^I‐mediated base pairs strongly depends on the sequence context. Quantum mechanical/molecular mechanical (QM/MM) calculations have been performed in order to gain insight into the factors determining this sequence dependence. The results indicated that, in addition to the stabilizing effect that results from the formation of coordinative bonds, destabilizing effects may occur when the artificial base pair does not fit optimally into the surrounding B‐DNA duplex.     

Working group report: High energy and collider physics

This is a summary of the projects undertaken by the working group I on high energy and collider physics.     

ZnS nanoparticle decorated ZnO nanowall network: investigation through electron microscopy and secondary ion mass spectrometry

We report on the fabrication of ZnO nanowall networks decorated with ZnS nanostructures on aluminum substrates using simple chemical route. The structural features and elemental constituents of the ZnS/ZnO heterostructure systems have been extensively studied using electron microscopy and energy dispersive X‐ray spectroscopy. The light emission characteristics of the bare and heterostructured systems have been analyzed using room temperature photoluminescence spectroscopy. The decoration of ZnS nanostructures over ZnO nanowalls has been evidenced through secondary ion mass spectrometry (SIMS). The ‘matrix effect’ has been found to be prominent during SIMS analysis of the bare and heterostructured nanowalls indicating the presence of ZnS phase over ZnO surface. ‘MCs⁺‐SIMS’ has been employed to suppress the matrix effect and is found to be potentially effective in making a semi‐quantitative estimation of Zn and O surface–atom concentrations in both systems. The luminescence responses of the ZnS/ZnO heterostructures have been found to be strongly dependent on the extent of ZnS phase over ZnO. The higher luminescence responses in ZnS/ZnO heterostructures fabricated with smaller ZnS nanoparticles have been explained in terms of a mechanism of charge‐carrier transfer from ZnS to ZnO. Copyright © 2014 John Wiley & Sons, Ltd.     

Diameter-dependent coercivity of cobalt nanowires

We show that the coercivity of electrochemically grown cobalt nanowires (NWs) within the pores of a polycarbonate membrane can be changed to a large extent by tuning their diameters. The face centered cubic crystalline structure of the NWs having diameter in the range of 10 to 200 nm could be retained. Smaller diameter wires (below 30 nm) are found to be single crystalline and oriented in the [110] growth direction, but for higher diameter wires the crystallite size became very small. Magnetization measurements with an applied field parallel to the axis of the NWs show that the nature of the M–H loop changes from square to linear as the diameter of the NWs increases. The coercivity was found to be 1700 Oe and 480 Oe at 5 K (1000 Oe and 250 Oe at 300 K) for 10 nm and 100 nm wires, respectively. The observed changes in the nature of the M–H loop and in coercivity could be explained following the Stoner–Wohlfarth model and using the fact that the domain size reduces as the diameter of the wires increases.     

Searches for the appearance of \nu_\tau using neutrino beams from muon storage rings

We study the possibilities offered by muon storage rings for appearance experiments in order to determine masses and mixing angles for the and oscillations. The dependence of tau event rates on baseline, forward peaking of decay neutrinos with increasing energies, and average fluxes intercepted by detectors of various sizes is discussed. It is found that the baseline length does not significantly affect the rates for oscillations of such magnitudes as are suggested by the current atmospheric neutrino data. Subsequently, the effects of cuts on hadronic and wrong sign leptonic modes are computed and used to plot 90% CL contours for the parameter regions that can be explored in such experiments. The results show that even for modest muon beam energies, convincing coverage and verification of the Super Kamiokande parameters is possible. In addition, a very significant enlargement of present day bounds on the mixing parameters for neutrino oscillations of all types is guaranteed by these types of searches. Received: 4 April 2000 / Revised version: 22 July 2000 / Published online: 8 December 2000