Interaction Of Alkali Metals Research Articles

An in-situ spectroscopy investigation of alkali metal interaction mechanism with the imide functional group

Organic anode materials have attracted considerable interest owing to their high tunability by adopting various active functional groups. However, the interaction mechanisms between the alkali metals and the active functional groups in host materials have been rarely studied systematically. Here, a widely used organic semiconductor of perylene-3,4,9,10-tetracarboxylic diimide (PTCDI) was selected as a model system to investigate how alkali metals interact with imide functional groups and induce changes in chemical and electronic structures of PTCDI. The interaction at the alkali/PTCDI interface was probed by in-situ X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), synchrotron-based near edge X-ray absorption fine structure (NEXAFS), and corroborated by density functional theory (DFT) calculations. Our results indicate that the alkali metal replaces the hydrogen atoms in the imide group and interact with the imide nitrogen of PTCDI. Electron transfer induced gap states and downward band-bending like effects are identified on the alkali-deposited PTCDI surface. It was found that Na shows a stronger electron transfer effect than Li. Such a model study of alkali insertion/intercalation in PTCDI gives insights for the exploration of the potential host materials for alkali storage applications.

Time scale analysis of the homogeneous flame inhibition by alkali metals

A time scale analysis of the homogeneous flame inhibition problem is carried out to identify the main parameters controlling the gas phase chemical interaction of the alkali metal inhibitors with the flame chemistry. First, kinetic sub-models for the interaction of alkali metals with the flame are analyzed to show that a simplified 2-step inhibition cycle can capture the essential features of this interaction. Second, it is shown that this cycle is auto-catalytic, which explains the high efficiency of alkali metals in inhibiting flames even at low concentrations. Third, the time scales associated to this inhibition cycle are linked to the free flame termination time scale via a non-dimensional parameter characterizing the efficiency of an inhibitor at promoting radical scavenging. It is shown that this parameter accounts for the main trends observed in the literature and can also be used to provide estimates for the chemical flame suppression limit.

A computational study on the endohedral alkali metal and ion B40 nanocluster

Recent exploration of the boron fullerenes has raised exciting new prospects for boron applications. Here, the endohedral X/X+@B40 complexes (X = Li, Na, and K) were explored by means of density functional theory calculations. By increasing the atomic number, the interaction of alkali metals with the B40 nanocage is unusually weakened. It was concluded that by increasing the alkali metals' size, their electrons repel those of the cage, and the interaction weakens. The interaction of X with B40 is more favorable than that of X+. For example, the calculated ΔG of interaction at 298K and 1atm is about -108.3 and + 18.4kJ mol-1 for X and X+, respectively. Compared to the X+ cations, the X atoms considerably enhance the boron cluster electrical conductivity, by reducing the gap. We found that the B40 nanocluster is not large enough to freely embed large atoms, such as Na and K. Also, the electron emission from the surface of B40 cluster is increased and reduced by X and X+ encapsulations, respectively.

Nonlinear Optical (NLO) Response of Si12C12 Nanocage Decorated with Alkali Metals (M = Li, Na and K): A Theoretical Study

Electronic structure and nonlinear optical (NLO) response of Si12C12 nanocage decorated with alkali metals (M = Li, Na and K) are investigated by means of density functional theory (DFT) and second order Moller–Plesset (MP2) calculations with 6 − 31 + G(d) basis set. The results of present study indicate that interaction of alkali metals with Si12C12 nanocage narrow the HOMO–LUMO gap of nanocage remarkably. It is shown that, decoration of Si12C12 with alkali metals play significant role in enhancement of first hyperpolarizability (β0) and consequence NLO response of Si12C12 nanocage.

Coordination chemistry insights into the role of alkali metal promoters in dinitrogen reduction

The Haber-Bosch process is a major contributor to fixed nitrogen that supports the world's nutritional needs and is one of the largest-scale industrial processes known. It has also served as a testing ground for chemists' understanding of surface chemistry. Thus, it is significant that the most thoroughly developed catalysts for N2 reduction use potassium as an electronic promoter. In this review, we discuss the literature on alkali metal cations as promoters for N2 reduction, in the context of the growing knowledge about cooperative interactions between N2, transition metals, and alkali metals in coordination compounds. Because the structures and properties are easier to characterize in these compounds, they give useful information on alkali metal interactions with N2. Here, we review a variety of interactions, with emphasis on recent work on iron complexes by the authors. Finally, we draw conclusions about the nature of these interactions and areas for future research.

Alkali Ion Incorporation into V2O5: a Noncovalent Interactions Analysis

Understanding the interaction of alkali metals with layered materials like vanadia is important for a range of technological applications such as energy storage and heterogeneous catalysis. Here we used the NCI (noncovalent interactions) index to analyze the nature of the chemical bonding between inserted alkali atoms (Li, Na, and K) and vanadia. We found that alkali atoms ionize in bulk vanadia making directional ionic bonds with neighboring oxygen atoms, whereas the dispersive interactions between vanadia layers remain unmodified by the presence of alkali ions. Interestingly, we show how the NCI analysis discriminates among the different vanadium–oxygen types of bond, capturing even finer interactions involving reduced vanadium sites or ring stabilization. In addition, we explored dynamic effects, concluding that the directionality of all interactions is preserved at 500 K.

(Lithiumbenzazaphospholine-2-carboxylate-κP)Rh(COD)Cl] — The first structurally characterized phosphinoalkanoate RhCl complex with Rh–Cl…alkali metal interactions

Addition of tBuLi at the PC bond of 1-neopentyl-1H-1,3-benzazaphosphole in toluene, followed by reaction with carbon dioxide, separation of the lithium benzazaphospholine-2-carboxylate 1Li and reaction with a semi-equivalent of [Rh(1,5-COD)Cl]2 in THF provided the tetrameric title complex 2Li, characterized by crystal structure analysis, rather than the expected Rh(1,5-COD) phosphinocarboxylate κ2P,O-chelate. 2Li is the first example of a κP-coordinated RhCl complex of an alkali metal phosphinoalkanoate; in the solid state, it forms crystal tetrameric aggregates involving Li…O and Li…Cl–Rh–P bridging interactions.

The influence of alkali metals (Li, Na and K) interaction with Be12O12 and Mg12O12 nanoclusters on their structural, electronic and nonlinear optical properties: A theoretical study

Density functional theory (DFT) calculations have been carried out to study the influence of alkali metals (Li, Na and K) interaction with Be12O12 and Mg12O12 nanoclusters on their structural, electronic and nonlinear optical properties. The interaction of Li, Na and K atoms is found to be remarkably narrowed the HOMO–LUMO gaps of the considered clusters. The electronic properties of these clusters are strongly sensitive to interaction with the alkali metals. Moreover, the encapsulation of alkali metals inside of the considered clusters slightly enhances their hyperpolarizabilities with one exception. The encapsulation of Li atom inside of the Mg12O12 nanocluster is energetically favorable and leads to a large hyperpolarizability. Furthermore, the adsorption of the alkali metals on the surface of the considered nanoclusters is investigated. The alkali metals adsorption on the surfaces of the clusters is energetically favorable and causes extremely large nonlinear optical (NLO) response in comparison to encapsulated forms. Therefore, the interaction of alkali metals with Be12O12 and Mg12O12 nanoclusters plays an important role in tuning their electronic and nonlinear optical properties. This work theoretically devises novel multifunctional inorganic metal oxide-based nanostructures via interaction with alkali atoms, which could be promoted their potential applications in electronic devices and high-performance NLO materials.

Computational study of interaction of alkali metals with C3N nanotubes

Interaction of the alkali metals (AMs) like lithium (Li), sodium (Na), and potassium (K) with defective and non-defective (8,0) C3N nanotubes (C3NNT) have been investigated using the first-principles study. In addition to structural properties, we have also studied the electronic properties, charge transfer, and work function of the AM-C3NNT complexes. AMs are adsorbed on hollow sites, regardless of the initial positions. Upon the adsorption of AMs, the structures exhibit semiconducting behavior. Furthermore, interaction of Li atom can be explained by Dewar model, whereas for the other atoms there are different explanations. For all metal adsorbates, the direction of the charge transfer is from adsorbate to adsorbent, because of their high surface reactivity. The results showed that the nanotube with carbon vacancy is the most favorite adsorbent. Our findings also indicated that the enhancement in absolute adsorption energy is in order of Li > K > Na. It is noteworthy that clustering of AM atoms on the nanotubes with and without defects is not expected. It is worthy that C3NNT is a better adsorbent for AM atoms than CNT, graphene, C60, and B80.

Sodium Ion Interactions with Aqueous Glucose: Insights from Quantum Mechanics, Molecular Dynamics, and Experiment

In the last several decades, significant efforts have been conducted to understand the fundamental reactivity of glucose derived from plant biomass in various chemical environments for conversion to renewable fuels and chemicals. For reactions of glucose in water, it is known that inorganic salts naturally present in biomass alter the product distribution in various deconstruction processes. However, the molecular-level interactions of alkali metal ions and glucose are unknown. These interactions are of physiological interest as well, for example, as they relate to cation-glucose cotransport. Here, we employ quantum mechanics (QM) to understand the interaction of a prevalent alkali metal, sodium, with glucose from a structural and thermodynamic perspective. The effect on β-glucose is subtle: a sodium ion perturbs bond lengths and atomic partial charges less than rotating a hydroxymethyl group. In contrast, the presence of a sodium ion significantly perturbs the partial charges of α-glucose anomeric and ring oxygens. Molecular dynamics (MD) simulations provide dynamic sampling in explicit water, and both the QM and the MD results show that sodium ions associate at many positions with respect to glucose with reasonably equivalent propensity. This promiscuous binding nature of Na(+) suggests that computational studies of glucose reactions in the presence of inorganic salts need to ensure thorough sampling of the cation positions, in addition to sampling glucose rotamers. The effect of NaCl on the relative populations of the anomers is experimentally quantified with light polarimetry. These results support the computational findings that Na(+) interacts similarly with α- and β-glucose.

Localized crystallization of polyfurfuryl alcohol derived carbon by alkali metals

The interaction of alkali metals with polyfurfuryl alcohol (PFA) derived nanoporous carbon (PFA-NPC) leads to localized regions of crystallization within the carbon. This is interesting because PFA-derived carbon is well known to be non-graphitizing, meaning that it does not tend to crystallize even at very high temperature (>2500°C). However, it has been demonstrated that after an oxidation with carbon dioxide, the PFA-NPC will crystallize at lower temperatures. Here, we show that localized crystallization of non-crystalline carbon takes place in the presence of each of the alkali metals, except lithium, under apparently mild conditions. At the local level, as adduced by HRTEM and electron diffraction analyses, cesium showed the greatest extent of ordering when compared to other alkali metals. However, when the materials are probed with bulk analyses, (X-ray diffraction, Raman spectroscopy, and NEXAFS), we do not observe evidence of gross crystallization. Therefore, it is our conclusion that local ordering occurs upon exposure of the alkali-containing PFA-NPC samples to air and that it occurs at the edges of the carbon particles. The ordering takes place as the alkali metals combust. We also conclude that carbons do not combust because the rate of oxygen transport into the sample is slowed by resistance in the nanopores as well as the resistance induced by the temperature gradient at the near surface region. Both phenomena prevent the gross combustion of the particle.

K-Ar Age Constraints on the Origin Of Micaceous Minerals in Savannah River Site Soils, South Carolina, USA

AbstractK-Ar measurements were used in this study of upland Savannah River Site soils to distinguish between sorbed K and the K remaining in remnants of primary minerals. Study of sorbed K contributes to understanding further the interaction of alkali metals (Cs in particular) with the soils. Primary mineral K and the associated radiogenic Ar were studied to characterize soil mica with respect to its provenance and its relationship to hydroxy-interlayered vermiculite. K-Ar age values of Na-saturated clay fractions from five samples of these soils range in age from 270 to 370 Ma. After a moderate acid treatment (6% HNO3 v/v, ~1 mol dm-3, 3 h, 80°C) of the clay fractions, K-Ar age values (270-325 Ma) were little changed on the whole, but they were more closely grouped near 300 Ma. Earlier work had shown that most of the K in these soils is found in material resistant to moderate acid extraction. The K-Ar age values show that this acid-resistant material is much older than any pedogenic minerals could be, even much older than the sedimentary parent rocks from which the soils were derived. These observations support earlier inferences by others that the K in these well leached soils is largely in remnants of primary muscovite from the parent sediments. Age values near 300 Ma suggest that the muscovite is largely from proximal Piedmont terranes of the Appalachian orogen, where the K-Ar relationship in most micas was set by Alleghanian tectonic processes late in the Paleozoic Era. The structural location of the K within mica, shown by the retention of the associated radiogenic Ar, is in contrast to the sorption-dominated behavior of the Cs and most of the Rb in these soils during pedogenesis. Stronger acid treatment (~6 mol dm-3 HNO3, 3 h, 100°C) extracted substantial fractions of both the K and the radiogenic Ar from bulk-soil portions, indicating destruction of some of the primary mica. K-Ar age values for the sand-rich bulk soils were not useful for this study because the sand contains excess radiogenic Ar, probably in sand-sized vein quartz.

The Alkali Metal Interactions with MgO Nanotubes

Adsorption of alkali metals (Li, Na, and K) on the surface of magnesium oxide nanotubes (MgONTs) with different diameters was investigated using density functional theory. According to the obtained results, the most stable adsorption site was found to be atop the oxygen atom of the tube surface with adsorption energies in the range of -0.25 to -0.74 eV. HOMO-LUMO gap () of the tubes dramatically decreases upon the adsorption of the alkali metals, resulting in enhancement of their electrical conductivity enhancement. The order of decrement caused by the metal adsorption is as follows: K > Na > Li. The results suggest that the MgONTs were transformed from semi-insulator to semiconductor upon the alkali metal adsorption. Increasing the tube diameter, the HOMO/LUMO gap of the pristine tube is enhanced and adsorption energies of the alkali metals are decreased.

Interaction of alkali metals with the Fe3O4(1 1 1) Surface

The adsorption and interaction of alkali metals (Li, Na, K, Rb and Cs) with the Fetet1-terminated Fe3O4(111) surface have been computed at the level of density functional theory. At low coverage, adsorption of alkali metals on site-1 (Oa–Oc–Od) is energetically more favorable than on site-2 (Oa–Oc–Od). Li has the strongest adsorption energy, followed by K, Rb, Cs and Na. The computed net charges show that the alkali metals can donate electrons to surface Fe and O atoms in the order of Li<Na<K≈Rb≈Cs. It is also noted that increasing the coverage does not significantly improve the promoting effect of alkali metals. In addition, alkali metals can move facilely on the Fe3O4(111) surface.

Fluorine⋅⋅⋅ and π⋅⋅⋅Alkali Metal Interactions Control in the Stereoselective Amide Enolate Alkylation with Fluorinated Oxazolidines (Fox) as a Chiral Auxiliary: An Experimental and Theoretical Study

The alpha-alkylation of amide enolates by using a pseudo-C(2) symmetry trans 4-phenyl-2-trifluoromethyloxazolidine (trans-Fox) as a chiral auxiliary occurs with an extremely high diastereoselectivity (>99 % de). The origin of this excellent stereocontrol was investigated by an experimental and theoretical (DFT) study. With this trans chiral auxiliary, both F...metal and pi...metal interactions compete to give the same diastereomer through Re face alkylation of the enolate. A 5.5 kcal mol(-1) energy difference found between the Re face and the Si face attack transition states is consistent with the complete diastereoselectivity that has been experimentally achieved. On the other hand, in the case of the cis chiral auxiliary (cis-Fox) the competition between the F...metal and pi...metal interactions is unfavourable to the diastereoselectivity. In this case, the Re face and the Si face attack transition states were found to be nearly isoenergetic (0.3 kcal mol(-1) difference), which is in good agreement with the very low diastereoselectivity observed.

Interaction of alkali metals with perylene-3,4,9,10-tetracarboxylic-dianhydride thin films studied by IR spectroscopy

In order to clarify the doping behavior of different alkali metals in perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA), Fourier transform infrared spectra of PTCDA thin films doped with sodium, potassium, and cesium were measured and compared. Furthermore the vibrational properties were calculated using density-functional theory and these calculated vibrational frequencies were assigned to the experimental IR modes of the thin films.

Interaction of alkali metals with perylene-3,4,9,10- tetracarboxylic–dianhydride thin films

n doping of the molecular organic semiconductor perylene-3,4,9,10-tetracarboxylic–dianhydride (PTCDA) is often achieved by use of alkali metals as dopants. This doping process is commonly performed in two steps. In the first the dopant is evaporated onto the surface of the PTCDA film. As it has been believed that the dopant shows an inhomogeneous diffusion profile through the layer with most of the dopant accumulated in the first few layers, a subsequent annealing step has been performed in order to reach a homogeneous distribution of the dopant in the whole layer. In this paper experimental results concerning chemical composition ((angle resolved) X-ray photoemission spectroscopy, secondary-ion-mass spectrometry, Fourier transform infrared spectroscopy), electronic structure (ultraviolet photoemission spectroscopy, inverse photoemission spectroscopy), as well as electrical properties (conductivity, Seebeck coefficient) are shown before and after doping and before and after annealing. These results suggest that the deposited dopant is redistributed and partially removed during the annealing step. A model for the dopant distribution is suggested.

Synthesis and solution properties of phthalocyanines substituted with four crown ethers

Metal-free and metal phthalocyanines (M = Ni, Zn, Co) substituted with four benzo-15-crown-5 units through oxy-bridges have been synthesized from a new phthalonitrile derivative, 1-{[(benzo-15-crown-5)-4′-yl]oxy}phthalonitrile ( 3). The newly prepared compounds have been characterized by elemental analyses, IR, 1H NMR, MS and UV–Vis spectroscopy. Alkali metal interactions of the crown ethers on the zinc phthalocyaninato ( 6) are shown to form intermolecular adduct. The electrochemical properties of ZnPc were investigated by using cyclic voltammetry and controlled potential coulometry.

Low-energy electron diffraction study of potassium adsorbed on single-crystal graphite and highly oriented pyrolytic graphite

Potassium adsorption on graphite has been a model system for the understanding of the interaction of alkali metals with surfaces. The geometries of the $(2\ifmmode\times\else\texttimes\fi{}2)$ structure of potassium on both single-crystal graphite (SCG) and highly oriented pyrolytic graphite (HOPG) were investigated for various preparation conditions for graphite temperatures between 55 and 140 K. In all cases, the geometry was found to consist of $\mathrm{K}$ atoms in the hollow sites on top of the surface. The $\mathrm{K}$-graphite average perpendicular spacing is $2.79\ifmmode\pm\else\textpm\fi{}0.03\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}}$, corresponding to an average $\mathrm{C}\text{\ensuremath{-}}\mathrm{K}$ distance of $3.13\ifmmode\pm\else\textpm\fi{}0.03\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}}$, and the spacing between graphite planes is consistent with the bulk spacing of $3.35\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}}$. No evidence was observed for a sublayer of potassium. The results of dynamical LEED studies for the clean SCG and HOPG surfaces indicate that the surface structures of both are consistent with the truncated bulk structure of graphite.

Theoretical investigation of the interaction of uracil and mono hydrated uracil – water complexes with alkali metals

Quantum chemistry calculations have been applied in order to explore the interaction of alkali metals with oxo groups of uracil. The optimised geometries, harmonic vibrational frequencies and the energies of uracil, metalated uracil, monohydrated uracil and monohydrated metalated uracil have been calculated. The calculations show that interaction of metals with uracil through O3 (UO3) is stronger than the interaction of metals with O1 (UO1). The presence of water stabilises the UO1, UO3 structures. In mono-hydrated uracil the stability of UO3W rather than UO1W is more than for non hydrated spices. Calculations show that after monohydration, the frequency shift of the stretching vibrations of N6-H is related to the atomic number of the metal.