Electrides, Negatively Charged Metal Ions, and Related Phenomena

Dye, James

doi:10.1002/9780470166338.ch4

Cited by 70 publications

(12 citation statements)

References 276 publications

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“…The synthesis of Li + (C211)Cs - proceeded as follows: 1.4 mmol of lithium and C211 were placed on one side of a two-chambered K-cell, , and 1.4 mmol of cesium was placed in a sidearm on the opposite side. The cesium was distilled to form a mirror, and the sidearm was sealed off from the K-cell.…”

Section: Experimental Methodsmentioning

confidence: 99%

“…Alkalides are a unique class of ionic salts that have alkali metal anions (where M - is Na - , K - , Rb - , or Cs - ) as the negative ions and alkali cations embedded in cryptands, crown ethers, or their aza analogues as the positive counterions. − Coulombic attraction between the complexed cations and M - anions stabilizes the salt, but we would expect Coulomb repulsion between the anions to keep them separated from one another. Yet, of the 37 published alkalide crystal structures, five have alkali metal anions in close proximity at distances smaller than the sum of the van der Waals radii .…”

Section: Introductionmentioning

confidence: 99%

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One-Dimensional Zigzag Chains of Cs^-: The Structures and Properties of Li⁺(Cryptand[2.1.1])Cs^- and Cs⁺(Cryptand[2.2.2])Cs^-

et al. 2006

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The crystal structure and properties of lithium (cryptand[2.1.1]) ceside, Li+ (C211)Cs-, are reported. Li+ (C211)Cs- is the second ceside and third alkalide with a one-dimensional (1D) zigzag chain of alkali metal anions. The distance between adjacent Cs- anions, 6 A, is shorter than the sum of the van der Waals radii, 7 A. Optical, magic angle spinning NMR, two-probe alternating and direct current conductivity, and electron paramagnetic resonance measurements reveal unique physical properties that result from the overlap of adjacent Cs- wave functions in the chain structure. The properties of cesium (cryptand[2.2.2]) ceside, Cs+ (C222)Cs-, were also studied to compare the effects of the subtle geometric changes between the two 1D zigzag chain structures. Li+ (C211)Cs- and Cs+ (C222)Cs- are both low-band-gap semiconductors with anisotropic reflectivities and large paramagnetic 133Cs NMR chemical shifts relative to Cs- (g). An electronic structure model consistent with the experimental data has sp2-hybridized Cs- within the chain and sp-hybridized chain ends. Ab initio multiconfiguration self-consistent field calculations on the ceside trimer, Cs3(3-), support this model and indicate a net bonding interaction between nearest neighbors. The buildup of electron density between adjacent Cs- anions is visualized through an electron density difference map constructed by subtracting the density of three cesium atoms from the short Cs3(3-) fragment.

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Section: Experimental Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

One-Dimensional Zigzag Chains of Cs^-: The Structures and Properties of Li⁺(Cryptand[2.1.1])Cs^- and Cs⁺(Cryptand[2.2.2])Cs^-

et al. 2006

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“…[Ca 24 Al 28 O 64 ] 4+ ( e − ) 4 , or C12A7: e − for brevity141516, is an electride171819, that is, a material in which electrons serve as anions. As shown in Fig.…”

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confidence: 99%

Activation and splitting of carbon dioxide on the surface of an inorganic electride material

et al. 2013

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Activation of carbon dioxide is the most important step in its conversion into valuable chemicals. Surfaces of stable oxide with a low work function may be promising for this purpose. Here we report that the surfaces of the inorganic electride [Ca24Al28O64]4+(e−)4 activate and split carbon dioxide at room temperature. This behaviour is attributed to a high concentration of localized electrons in the near-surface region and a corrugation of the surface that can trap oxygen atoms and strained carbon monoxide and carbon dioxide molecules. The [Ca24Al28O64]4+(e−)4 surface exposed to carbon dioxide is studied using temperature-programmed desorption, and spectroscopic methods. The results of these measurements, corroborated with ab initio simulations, show that both carbon monoxide and carbon dioxide adsorb on the [Ca24Al28O64]4+(e−)4 surface at RT and above and adopt unusual configurations that result in desorption of molecular carbon monoxide and atomic oxygen upon heating.

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“…Electrides are crystalline salts in which electrons act as anions. , Conventionally, electrides have been synthesized using alkali metal adducts of organic molecules , or inorganic molecular sieves. − However, they are chemically and thermally unstable and decompose in inert atmospheres at temperatures above −40 °C or in an ambient atmosphere at lower temperatures by reactions with O 2 and/or H 2 O.…”

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confidence: 99%

Surface of Room-Temperature-Stable Electride [Ca₂₄Al₂₈O₆₄]⁴⁺(e⁻)₄: Preparation and Its Characterization by Atomic-Resolution Scanning Tunneling Microscopy

Yoshitake

Kubota²,

Hirano

et al. 2011

ACS Nano

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The nanocage compound crystal [Ca24Al28O64]4+(e-)4 (C12A7:e-) is a room-temperature-stable electride. Although bulk C12A7:e- exhibits metallic conduction, the surface of an as-prepared sample or one prepared by mechanical fracture in ultrahigh vacuum is almost insulating and exhibits distinct non-ohmic contact. We studied whether the intrinsic surface of this electride exhibits metallic conduction or not by examining various conditions for preparing the intrinsic surface. A combination of sputtering with thermal annealing led to the emergence of metallic conductivity in a specific condition. Suitably prepared surfaces revealed ohmic contact even in an ambient atmosphere. Atomic-resolution scanning tunneling microscopy (STM) images of the surfaces were consistent with a structural model in which the cage structure in the bulk C12A7:e- electride is conserved at the surface.

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Electrides, Negatively Charged Metal Ions, and Related Phenomena

Cited by 70 publications

References 276 publications

One-Dimensional Zigzag Chains of Cs^-: The Structures and Properties of Li⁺(Cryptand[2.1.1])Cs^- and Cs⁺(Cryptand[2.2.2])Cs^-

One-Dimensional Zigzag Chains of Cs^-: The Structures and Properties of Li⁺(Cryptand[2.1.1])Cs^- and Cs⁺(Cryptand[2.2.2])Cs^-

Activation and splitting of carbon dioxide on the surface of an inorganic electride material

Surface of Room-Temperature-Stable Electride [Ca₂₄Al₂₈O₆₄]⁴⁺(e⁻)₄: Preparation and Its Characterization by Atomic-Resolution Scanning Tunneling Microscopy

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Electrides, Negatively Charged Metal Ions, and Related Phenomena

Cited by 70 publications

References 276 publications

One-Dimensional Zigzag Chains of Cs-: The Structures and Properties of Li+(Cryptand[2.1.1])Cs- and Cs+(Cryptand[2.2.2])Cs-

One-Dimensional Zigzag Chains of Cs-: The Structures and Properties of Li+(Cryptand[2.1.1])Cs- and Cs+(Cryptand[2.2.2])Cs-

Activation and splitting of carbon dioxide on the surface of an inorganic electride material

Surface of Room-Temperature-Stable Electride [Ca24Al28O64]4+(e−)4: Preparation and Its Characterization by Atomic-Resolution Scanning Tunneling Microscopy

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One-Dimensional Zigzag Chains of Cs^-: The Structures and Properties of Li⁺(Cryptand[2.1.1])Cs^- and Cs⁺(Cryptand[2.2.2])Cs^-

One-Dimensional Zigzag Chains of Cs^-: The Structures and Properties of Li⁺(Cryptand[2.1.1])Cs^- and Cs⁺(Cryptand[2.2.2])Cs^-

Surface of Room-Temperature-Stable Electride [Ca₂₄Al₂₈O₆₄]⁴⁺(e⁻)₄: Preparation and Its Characterization by Atomic-Resolution Scanning Tunneling Microscopy