MBAMT,a new locating and chelating agen in TLC and ring colorimetric determination of Cu(II), Co(II), Ni(II), Pd(II), Pt(IV), and Rh(III)

Summary Synthesis of MBAMT (3-methyl-4-benzylideneamino-5-mercapto-1,2,4-triazole) and its IR and NMR spectral data are reported. The high stability of the characteristically coloured chelates with Cu(II), Co(II), Ni(II), Pd(II), Pt(IV) and Rh(III) has been made the basis for their efficient ascending TLC separations on silica gel G layers, when present together. Results of four different solvent systems are included to assess efficient resolution of the chelates along with their limits of identification and separation. TLC separations, followed by the ring colorimetric determination of the six metal ions (as ternary mixtures) are tabulated.MBAMT=3-methyl-4-benzylideneamino-5-mercapto-1,2,4-triazole.     

Self consistent modified extended Hückel (SC-MEH) calculations on heavy metal systems. I. Platinum(II) tetragonal planar complexes with and without relativistic effects

The Self Consistent Modified Extended Hückel molecular orbital method had been applied to several square planar complexes of platinum (II). Calculations including both the limited 5d, 6s, 6p and extended 5s, 5p, 5d, 6s, 6p starting bases for platinum were made. It is shown that in PtCl ₄ ^2– both the nuclear quadrupole moment and minimum total energy vs. bond distance are calculated to be in good agreement with experiment, only with the extended platinum AO basis.Specific inclusion of relativistic parameters via a pseudo-relativistic approximation are shown to have a significant effect on the energy molecular energy levels, however no meaningful rationalization can be made without the simultaneous inclusion of ligand field parameters as well.Supported in part by a grant made available through the Cancer Association of Greater New Orleans. Use of the facilities of the Computer Research Center of the University of New Orleans is gratefully acknowledged.     

Oxidation of Organometallic Compounds

Stable organometallic compounds, notably of the later transition metals (groups VI–VIII), usually are characterized by closed shell electron configurations (typically 18-electron valence shells) which are destabilized by electron addition or removal. One-electron oxidation of such compounds results in the formation of unstable radical ions, whose characteristic reactivity patterns include susceptibility to nucleophilic attack, disproportionation, and metal-carbon bond dissociation. Two-electron oxidation may result in dissociation or oxidation of the organic ligand. In this review studies on the chemical and electrochemical oxidations of metal carbonyls, metal-olefin complexes, and alkyl transition-metal compounds are described. The studies encompass the following themes: (1) The kinetics and thermodynamics of the initial redox steps; (2) The characterization and reactivity patterns of the resulting oxidation products; (3) The synthetic and catalytic applications of organometallic redox processes.     

Solid-supported reagents and catalysts for the preparation of large ring compounds

Parallel combinatorial synthesis in solution using immobilized reagents, catalysts, and scavengers has emerged as a powerful technique for the preparation of diverse libraries of compounds. This technique has only recently been applied to the synthesis of large-ring compounds. In this comprehensive review several strategies are presented and discussed, including Pd-catalyzed allylic alkylation, Stille-coupling, macrolactonization and macrolactamization using solid supported reagents and catalysts. In several cases site isolation has allowed operation of these macrocyclization reactions in concentrated solution (pseudo-dilution effect).     

The Extended Surface as a Factor Forming Distinctive Features of Nanodimensional Media

As a result of studying thin-film nano-sized media, it is shown that the extended surface exerts a substantial influence on their distinctive properties. It has been established that, by using special methods to obtain nano-sized media under certain conditions, it is possible to form crystal structures with a high concentration of defects of a prescribed type in the near-surface layers of nanocrystals. The correlations found between the conducting and optical properties of thin-film nano-sized structures are an additional factor that extends the capabilities of controlling their characteristics with a view toward developing miniature effective radiation sources, elements of modulation of laser radiation, dosimeters, and components of thin-film solar cells. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 3, pp. 287–291, May–June, 2005.     

Ligand-ligand redox interaction through some metal-cluster units

The ligand-ligand redox interaction separated by di-, tri-, and hexanuclear cluster units is discussed in terms of the splitting of the redox waves (DeltaE(L)) and the comproportionation constants (Kcom(L)) of the ligand-based mixed valence state. Although two redox-active monodentate ligands in the mononuclear ruthenium(II) complexes (either cis or trans configurations) do not show appreciable splitting in their reduction waves, interestingly those separated by giant triruthenium and hexarhenium cluster units clearly show splitting. The molecular orbital considerations in the literature suggest that these units possess some pi-type molecular orbitals composed of metal dpi and possibly ligand ppi orbitals. Absence of the redox interactions in oxo-bridged diruthenium(II) and oxo-centered trirhodium(III) complexes where such pi molecular orbitals (including an antibonding one) are fully occupied, indicates the importance of empty pi* orbitals for the ligand redox communication.     

Surface Extension in Layered Structures with the Use of Metal Meshes for Heat-Transfer Enhancement

The properties of multilayer metal-fiber coverings superimposed on plane base layers, which consist of various combinations of a copper mesh and different-length copper wires, are examined. Coverings from discrete copper microwires, two-layer coverings including a mesh and microwires, and three-layer coverings consisting of a mesh and two layers of microwire are investigated. The contacts between the fibers, the copper mesh, and the base layer are analyzed by using the metallography technique. Quantitative estimates for these contacts are presented. The side effects connected with the hydrogen disease of copper are discussed. The thermal properties of the porous structures are analyzed with the use of a termographic chamber. It is shown that the porous metal-fiber structures have good mechanical and heat-transfer properties.     

Influence of Interorbital Interference on Tunneling Process in STM

We present a theoretical study of the influence of intra-atomic interorbital interference on the formation of STM images of metal surfaces. The obtained results show that this kind of interference may modify significantly the tunneling current by the increase or decrease of the current contributions flowing through different orbitals of the surface atoms. STM simulations performed for aluminium and nickel surfaces indicate that the height of corrugation and the topographies of STM images of different surfaces depend considerably on this interference.