Interaction Of Alkali Metals Research Articles

Time-of-flight-SIMS and XPS characterization of metal doped polymers

Organic thin films with defined chemical structures and physical properties are required for various applications. Plasma polymerization is of technological interest, since the deposition of plasma polymers is possible on any material of any shape in the desired thickness. We report on the TOF-SIMS (TOF: time-of-flight) and XPS investigations of pulse plasma ‘poly(acetylene)’ and alkali metal doped pulse plasma ‘poly(acetylene)’ films. The combination of TOF-SIMS and XPS supplies detailed information on the surface chemistry of these films. Application of both methods provides the possibility for cross-checking certain results. Moreover the different sensitivities of the methods can be utilized. According to the TOF-SIMS and XPS data it can be concluded that the interaction of alkali metals with plasma ‘poly(acetylene)’ results in electrovalent bonds of the type Me δ+ –C δ− between carbon and metal. Furthermore carbon–oxygen–metal interactions were observed. These interactions are of the type CO δ− ⋯Me δ+ and/or C–O δ− –Me δ+ .

Synthesis, characterization and aggregation behavior ofNi(II)andZn(II)phthalocyanines with peripheral monoazacrown ethers

The synthesis of metallo derivatives ( Ni , Zn ) of phthalocyanines (pcs) obtained from 4,5-dicyanobenzomonoazacrown ether substituted with long alkyl chains (5a-d) are described. The new compounds have been characterized by elemental analysis,1H ,13C NMR, MS, IR and UV-vis spectroscopy techniques. The aggregation properties and alkali metal interaction of the pcs (6a-d and 7a-d) were investigated.

Chemistry and physics of alkali metals on MoS2 surfaces

The interaction of alkali metal with surfaces has been of great interest to the community of catalysis since alkali metal can play an important role as a promoter. On alkali-doped MoS2, such a promotion effect of alkali metal has been exemplified in the direct synthesis of linear alcohols from CO and H2, where the alkali-doping switches the catalyst selectivity from methanation to alcohol synthesis. This paper reviews recent high-resolution X-ray photoelectron spectroscopy experiments that have provided directobservation of electron transfer from alkali metals to a model single crystal MoS2 and the capture of the supra-valence electrons in the subsequent oxidation reactions.

Porphyrazines with appending eight crown ethers

Porphyrazines (M=2H, Mg, Cu, Co or Zn) with eight crown ether groups appending on the periphery through flexible alkylthio-bridges have been synthesized through esterification of octakis (hydroxyethylthio)-porphyrazinatomagnesium with a carboxylic acid derivative of benzo-15-crown-5 in the presence of dicyclohexyl-carbodiimid. The new compounds have been characterized by elemental analysis and IR, 1H NMR, UV–Vis and mass spectral data. Alkali metal interaction of the crown ethers on the magnesium porphyrazinate ( 4) are shown to form intramolecular sandwich type adducts by the changes occurring after gradual portionwise addition of these salts into the porphyrazine solutions.

High-coverage adsorption of alkali metals at the CaO and MgO (100) surfaces

The interaction of alkali metals (Li and Na) with the defect-free (100) surface of CaO and MgO has been studied in the framework of density functional theory with periodic boundary conditions for the coverages 1.0 and 0.5 ML (Li) and 0.5 ML (Na). The lateral interaction among adsorbed alkali atoms contributes significantly to the stabilization of the metallic layer. The binding energy of Li for the 1.0 ML coverage is comparable for CaO and MgO and is larger than the cohesive energy of bulk Li. Hence, this monolayer is stable with respect to formation of a three-dimensional metallic island, and a small lattice mismatch between MgO(100) and the bcc Li indicates the possibility of creating a low-energy interface between these two materials under proper growth conditions. The chemical effects in the metal–substrate interaction are not significant.

Alkali metal reactions with Ni(110)–O and NiO(100) surfaces

The interaction of alkali metals (lithium, sodium, potassium) with an Ni(110)–O surface has been studied using X-ray photoelectron spectroscopy (XPS). The reaction at 300 K gives rise to a peroxide species together with a degree of reduction of the oxide to metallic nickel. With sodium an Ni(2p) feature attributed variously to Ni 3+ or a final-state effect for Ni 2+ is suppressed, consistent with its origins in an intersite screening process in NiO. At higher temperatures, lithium and potassium participate in a solid-state reaction with the oxide in which a trivalent nickel oxidation state (as LiNiO 2 and KNiO 2) is formed. Analogous reactions with sodium form the divalent nickelate Na 2NiO 2. Coadsorption of the alkali metal and oxygen on clean Ni(110) provides for optimum nickelate formation, whereas the presence of water inhibits the formation of Ni 3+ significantly. Similar experiments on NiO(100) suggest that the widespread practice of using thin oxide films to mimic bulk oxides may not always be justified.

Interaction of alkali metals with unsaturated heterocyclic compounds. The reductive metallation of 2,3,5,6‐tetraphenylpyrazine and the synthesis of 1,2‐dihydro‐1,4‐diazine derivatives

AbstractTreatment of 2,3,5,6‐tetraphenylpyrazine (1) with sodium in tetrahydrofuran effected the formation of monomeric dianion 2. The chemical behaviour of this new disodium adduct was characterized by a variety of reagents. Generally, the protonation (water), alkylation (methyl iodide and benzyl chloride), and acylation (methyl and ethyl chloroformate) products were 1,2‐dihydrotetraphenyldiazine derivatives. An annulation of the pyrazine ring system was accomplished by treating the dianion with polymethylene chlorides, Cl(CH2)nCl, n = 2, 3, 4.

Dissolving alkali metals in zeolites: genesis of the perfect cluster crystal

The interaction of alkali metals with dehydrated zeolites Y and A leads, in a process which bears many similarities to the dissolution of those metals in non-aqueous liquid solvemts, to the formation of inclusion compounds which may be regarded as ordered arrays of closely spaced clusters, and whose properties are dependent on interactions between the clusters. A combined analysis of electron spin resonance, magnetic susceptibility and powder neutron diffraction results enabled us to follow in detail the chemistry behind the formation of sodium- and potassium-based ‘cluster crystals’ in zeolites Y and A respectively.

Rotational distributions of excited CN molecules following electron- and photon-stimulated desorption from surfaces.

We report systematic experimental studies of rotational distributions of excited CN desorbed from alkali-metal and alkali-metal-halide surfaces following excitation by incident photons and electrons. Newly measured rotational spectra are found to exhibit temperature-independent non-Boltzmann features that are uniquely correlated to the particular alkali-metal component of the substrate. In addition, we observe that photon-excitation functions and cross sections for ${\mathrm{CN}}^{\mathrm{*}}$ desorption also depend strongly on the alkali-metal component of the substrate. The data reveal that rotational distributions arising from electron-stimulated desorption (ESD) and photon-stimulated desorption (PSD) are markedly different from those seen in thermal desorption and molecule-surface scattering. The marked substrate dependence of the rotational distributions indicates that molecular-rotation distributions following ESD and PSD are determined by direct electronic bond breaking and reflect the nature of the potential-energy surfaces that characterize CN--alkali-metal interactions. Utilizing the measured rotational distributions in conjunction with a hindered rotor model, we have constructed angular-dependent potential surfaces.

Progress into Understanding of Alkali Metal Interaction with a Silicon Surface

Progress into Understanding of Alkali Metal Interaction with a Silicon Surface

Interaction of alkali metals with Si(001)-2 x 1.

On effectue un ensemble extensif de calculs d'energie totale et des forces pour les metaux alcalins tels que Na et K adsorbes sur Si(001)-2×1 a des degres de recouvrement differents. La relaxation complete du reseau est effectuee en presence de couches adsorbees aux sites competitifs pour aboutir a la structure definitive. Comparaison de ces resultats aux autres resultats theoriques et experimentaux

Photoemission studies of the interaction of Li and solid molecular oxygen.

The interaction of Li and oxygen has been studied at 25 K. This system serves as an excellent prototype for studying the interaction of alkali metals with oxygen. For some of the alkali metals, such as Cs or K, oxygen can be incorporated below the metal surface and complex valence-band and core-level features are obtained. In the case of Li at 25 K this does not appear to happen, and the core-level and valence-band features can be identified with the formation of the superoxide, the peroxide, and the oxide.

Density functional study of the electronic properties of the Si (001)2x1-potassium surface

We have studied the interaction of alkali metals with Si(001)-2xl surface within the density functional formalism using the SCF pseudopotential method. Some experimental data which are subject to misinterpretation, coupled with our lack of knowledge about the exact adsorption structure, have led to some controversy about the nature of the K-Si bonding. We provide a resolution of some of these problems. We show that the active intrinsic surface states play a crucial role in determining the bonding between K and S(00 l)-2x 1. In particular, the overlayer metallization is suppressed even up to saturation coverages for this metal-semiconductor system.

Structure and mechanism of alkali-metal-induced reconstruction of fcc (110) surfaces.

A comprehensive model for the interaction of alkali metals with fcc (110) metals is presented for the first time. It is based on a direct comparison of K on the unreconstructed Ni and the missing-row reconstructed Au(110) surfaces. Regardless of initial substrate structure, two processes may occur: nonactivated adlayer ordering or local, activated substrate reconstruction via island growth. Coverage-dependent electrostatic interactions determine the substrate structure. Low alkali-metal-atom coverages favor a corrugated, reconstructed substrate; high coverages favor a relatively flat, unreconstructed substrate.

Interaction of alkali metals with semiconductors

We discuss the interaction of alkali metals with semiconductors with emphasis on the nature of bonding. The particular system chosen to illustrate our ideas is the adsorption of potassium on silicon surfaces. The tendency towards metallization as a function of coverage is shown to differ from that usually believed to occur for alkali metals on transition metals. It is found that alkali metals on semiconductors form a strong ionic bond even up to monolayer coverages. The metallization of the overlayer is shown to be energetically unfavorable due to the presence of the dangling bonds. Thus the overlayer metallization is either suppressed or occurs at rather high coverages. We suggest that the tendency towards metallization at high coverages is the surface analog of the ionic-metal transition discussed by Phillips.

ChemInform Abstract: Interaction of Alkali Metals with Unsaturated Heterocyclic Compounds.

Abstract1,4‐Diphenyl‐phthalazin (I) liefert ein Dianion (II), dessen Struktur diskutiert wird.

Interaction of alkali metals with unsaturated heterocyclic compounds. The reductive metalation of 1,4‐diphenylphthalazine

Abstract1,4‐Diphenylphthalazine (1) was reduced in tetrahydrofuran by sodium metal to a monomeric dianion 2. Chemical reactions of this new dianion were examined with various reagents. Generally, the protonation, acylation and alkylation products were 1,2‐dihydrophthalazine derivatives. An annulation of the phthalazine ring system was accomplished by treating the dianion with 1,3‐dichloropropane or 1,4‐dichlorobutane. With 1,2‐dichloroethane however, only 1,4‐diphenylnaphthalene was detected.

Cohesion and structure in stage-1 graphite intercalation compounds.

We have developed a Thomas-Fermi theory for the structural and elastic properties of the first-stage alkali-metal graphite intercalation compounds. We use a simplified model for the electronic structure of these materials which assumes full charge transfer between the alkali metal and the graphite, no hybridization between metal and carbon states, and a uniform distribution of the donated charge on the graphite planes. We have computed lattice constants, compressibilities, shear moduli, alkali-metal diffusion constants and activation energies, and domain-wall thicknesses; general agreement with available experiments is found. These results indicate that our model of the electronic properties is consistent with known elastic and structural properties. The interplane metal-carbon interaction is mostly determined by a competition between Coulomb attraction and hard-core repulsion. The Li ion is much more compact than that of K, Rb, or Cs, which explains the higher compressibility of the Li graphite intercalation compound and the lower Li ionic mobility. The Na--C bond is found to be very soft, explaining the lack of formation of Na-intercalated graphite. The in-plane alkali-metal--alkali-metal interaction is determined almost entirely by the Coulomb interaction, and is thus relatively independent of the alkali-metal species.

Interaction of alkali metals with unsaturated heterocyclic compounds. The reductive metalation of 3-phenylcinnoline

Interaction of alkali metals with unsaturated heterocyclic compounds. The reductive metalation of 3-phenylcinnoline

Interaction of Alkali Metal and Halide Vapors with Ceramic Materials

The effect of minor constituents in alumina arc tubes on lamp performance has been investigated. It is found that arc tubes containing calcia are less resistant to sodium vapor and accelerate early failures. Microstructural studies reveal extensive formation of β—alumina phases and sodium penetration across the wall of the reacted alumina. A number of other interactions, including calcia-doped MgAl2O4 spinel have been studied. Mechanisms of sodium migration in terms of structural defects and chemical constitution of the grain boundary are presented and discussed.