Coordination and structure of some transition metal piperidinium pentamethylene dithiocarbamate complexes

Summary Cobalt(II), nickel(ll), and copper(II) complexes of piperidinum pentamethylene dithiocarbamate (pipmdte) have been prepared and studied by spectral (i.r. and absorption) and magnetic methods. The M(pipmdte)CI complexes are probably four coordinate and square planar, the tridentate ligand being coordinated via the two thiocarbamate sulphur atoms and the nitrogen atom of the piperidinium group.     

518—π-acid effect on electrode behaviour of ternary complexes in solution: Complex formation between copper(II)-1,10-phenanthroline complex and ligands containing oxygen and/or nitrogen donor atoms as secondary ligands. part II

The study of mixed-ligand complexes [Cu_x(phen)_yL_z] (where phen stands for 1,10-phenanthroline and L for aliphatic acids, aromatic acids, amino acids and phenols in the ratio of 1 : 1 : 1 and 1 : 2 : 1) has been made at three different temperatures, namely 30, 35 and 40°C. It is observed that all the complexes follow a partictiar reaction mechanism with temperature, and the half-wave potential shifts towards the more positive side with rise of temperature, indicating easier reduction. Besides the formal rate constant, the activation energy of diffusion, E_D, has been calculated for each system. The effect of activation energy and the energy of rearrangement of electronic configuration of the depolarizer has been discussed against availability of the redox orbital for the electroreduction process.     

Effect of B-site dopants on magnetic and transport properties of LaSrCoRuO<Subscript>6</Subscript>

Effect of Co, Ru and Cu substitution at B and B’ sites on the magnetic and transport properties of LaSrCoRuO₆ have been investigated. All the doped compositions crystallize in the monoclinic structure in the space group P2₁/n indicating a double perovskite structure. While the magnetization and conductivity increase in Co and Ru doped compounds, antiferromagnetism is seen to strengthen in the Cu doped samples. These results are explained on the basis of a competition between linear Co-O-Ru-O-Co and perpendicular Co-O-O-Co antiferromagnetic interactions and due to formation of Ru-O-Ru ferromagnetic networks.     

Macropolyhedral boron-containing cluster chemistry. A synthetic approach via the auto-fusion of [6,9-(SMe2)2-arachno-B10H12

In an attempt to build up borane-based multicluster assemblies, thermolysis of [6,9-(SMe2)2-arachno-B10H12] 1 in inert hydrocarbon solution, followed by chromatographic separation, has resulted in the isolation not only of the previously established single-cluster product from this reaction, [5-(SMe2)-nido-B10H12] 2 (30%), but also the two two-cluster species [6,9-(SMe2)2-arachno-B10H11-1-(6-nido-B10H13)] 3 (20%) and [1,6-(nido-B10H13)2] 6 (ca. 0.5%) and the two three-cluster species [6,9-(SMe2)2-arachno-B10H10-1,5-(6-nido-B10H13)2] 4 (5%), characterized crystallographically, and [6,9-(SMe2)2-arachno-B10H10-1,3-(6-nido-B10H13)2] 5 (<1%), identified by NMR spectroscopy. An improved crystallographic investigation of [5-(SMe2)-nido-B10H12] 2 is also presented. The feasibility of the stability of species resulting from multiple adjacent substitution of nido-decaboranyl units on the [6,9-(SMe2)2-arachno-B10H12] skeleton is tested by DFT calculations. In an extension, to attempt the use of pre--linked two-cluster compounds as starting substrates, two-cluster [5-(SMe2)-4-(2-nido-B10H13)-nido-B10H11] 7 (0.6%) has been isolated from the reaction of SMe2 with [1,5-(nido-B10H13)2], other identified products being compound 1 (39%) and compound 3 (10.5%).     

Generation of excess minority carriers in mos devices due to gamma irradiation

The effect of gamma irradiation on MOS devices prepared under different oxidation conditions Is investigated. The C-V characteristics of the devices are studied before and after exposing the latter with gamma radiations of CO⁶⁰ (1.17 and 1.33 MeV gamma rays). For MOS transistor (n-channel depletion type devices) the C-V characteristics change slightly towards the negative voltage axis and the C_min also decreases after Irradiation. For MOS capacitor (wet oxide) there is a change from high frequency C-V characteristics to low frequency C-V characteristics. In the case of a MOS capacitor (HCl grown) breakdown occurs relatively at lower voltage.     

Innovative solution of a 2D elastic transmission problem¶

This article is concerned with a boundary-field equation approach to a class of boundary value problems exterior to a thin domain. A prototype of this kind of problems is the interaction problem with a thin elastic structure. We are interested in the asymptotic behavior of the solution when the thickness of the elastic structure approaches to zero. In particular, formal asymptotic expansions will be developed, and their rigorous justification will be considered. As will be seen, the construction of these formal expansions hinges on the solutions of a sequence of exterior Dirichlet problems, which can be treated by employing boundary element methods. On the other hand, the justification of the corresponding formal procedure requires an independence on the thickness of the thin domain for the constant in the Korn inequality. It is shown that in spite of the reduction of the dimensionality of the domain under consideration, this class of problems are, in general, not singular perturbation problems, because of appropriate interface conditions.     

Characterization of the 46.9-nm soft X-ray laser beam from a capillary discharge

Intense lasing had been obtained from argon plasma in the soft X-ray region from a capillary discharge plasma system. Different diagnostics have been used to characterize the lasing properties by recording the temporal, spatial, and spectral profiles of the emission. The divergence measurement indicates that the soft X-ray laser beam has good directionality with a divergence of 3.5 mrad. The spectrum of the laser beam measured using a transmission grating showed intense lasing line at 46.9 nm. Diffraction orders as high as 10th orders were observed. The temporal profile recorded with a vacuum diode showed a distinct laser peak with a pulse width ~1.2 ns (FWHM). In addition, the coherence of the X-ray laser beam was also confirmed from the high-contrast interference fringes (visibility ~85 %) recorded using double slits.     

Cationic ruthenium complex of the formula [RuCl(2,6-diacetylpyridine)(PPh3)2]BArF and its catalytic activity in the formation of enol esters

A new ruthenium 2,6-diacetylpyridine complex was synthesized and applied in the atom-economic synthesis of enol esters through Markovnikov-directed addition of carboxylic acids to terminal alkynes. The ruthenium complex [RuCl(dap)(PPh₃)₂]⁺BArF^? was synthesized from [RuCl₂(PPh₃)₂] and the corresponding ligand 2,6-diacetylpyridine (dap). The complex was characterized structurally. The new ruthenium complex was utilized under ambient conditions as a catalyst in the Markovnikov addition of carboxylic acids to terminal alkynes to afford the corresponding enol esters in 93% to 52% isolated yields (85?°C, 16?h reaction time, 1?mol% catalyst loading).     

Stream-lined synthesis of 3-hydroxy-β-lactams: Norrish-Yang type II photocyclizations of β-ketoformamides

A photochemical approach to 3-phenyl-3-hydroxy-β-lactams (3-HβLs) is reported. Irradiation of aryl-β-ketoformamides with a UV light band centered at 300?nm provides the corresponding 3-aryl-3-HβLs with good conversion. The scope of the photocyclization is explored with an electronically diverse panel of substrates that provides mechanistic insight supporting a Norrish-Yang type II cyclization. A flexible synthetic route to phenyl-β-ketoformamides, followed by photoirradiation, allows for efficient incorporation of the β-lactam pharmacophore into aromatic organic scaffolds. Taken collectively, the improved and optimized synthetic route to provide both β-ketoformamides and 3-HβLs—in combination with the expanded analysis of substrate scope and limitations—reported herein will serve as a necessary reference for the direct, atom-economical, radical-mediated installation of 3-HβL scaffolds en route to the generation of other biologically active small molecules.     

Metalloradical complexes of manganese and chromium featuring an oxidatively rearranged ligand

Redox events involving both metal and ligand sites are receiving increased attention since a number of biological processes direct redox equivalents toward functional residues. Metalloradical synthetic analogues remain scarce and require better definition of their mode of formation and subsequent operation. The trisamido-amine ligand [(RNC6H4)3N]3-, where R is the electron-rich 4-t-Bu Ph, is employed in this study to generate redox active residues in manganese and chromium complexes. Solutions of [(L1)Mn(II)-THF]- in THF are oxidized by dioxygen to afford [(L1re-1)Mn(III)-(O)2-Mn(III)(L1 re-1)]2-as the major product. The rare dinuclear manganese (III,III) core is stabilized by a rearranged ligand that has undergone an one-electron oxidative transformation, followed by retention of the oxidation equivalent as a pi radical in ano-diiminobenzosemiquinonate moiety. Magnetic studies indicate that the ligand-centered radical is stabilized by means of extended antiferromagnetic coupling between the S ) 1/2 radical and the adjacent S ) 2 Mn(III) site, as well as between the two Mn(III) centers via the dioxo bridge. Electrochemical and EPR data suggest that this system can store higher levels of oxidation potency. Entry to the corresponding Cr(III) chemistry is achieved by employing CrCl3 to access both[(L1)Cr(III)-THF] and [(L1re-1)Cr(III)-THF(Cl)], featuring the intact and the oxidatively rearranged ligands, respectively. The latter is generated by ligand-centered oxidation of the former compound. The rearranged ligand is perceived to be the product of an one-electron oxidation of the intact ligand to afford a metal-bound aminyl radical that subsequently mediates a radical 1,4-(N-to-N) aryl migration.