Inorganic electrides

It is also possible to prepare crystalline electrides in which a trapped electron acts in effect as the anion. The bnUc of the excess electron density in electrides resides in the X-ray empty cavities and in the intercoimecting chaimels. Stmctures of electri-dides [Li(2,l,l-crypt)]+ e [K(2,2,2-crypt)]+ e , [Rb(2,2,2-crypt)]+ e, [Cs(18-crown-6)2]+ e, [Cs(15-crown-5)2]" e and mixed-sandwich electride [Cs(18-crown-6)(15-crown-5)+e ]6 18-crown-6 are known. Silica-zeolites with pore diameters of vA have been used to prepare silica-based electrides. The potassium species contains weakly bound electron pairs which appear to be delocalized, whereas the cesium species have optical and magnetic properties indicative of electron locahzation in cavities with little interaction between the electrons or between them and the cation. The structural model of the stable cesium electride synthesized by intercalating cesium in zeohte ITQ-4 has been coirfirmed by the atomic pair distribution function (PDF) analysis. The synthetic methods, structures, spectroscopic properties, and magnetic behavior of some electrides have been reviewed. Theoretical study on structural and electronic properties of inorganic electrides has also been addressed recently. ... 

We recently added alkali metals from the vapor phase to two pure silica zealots to yield adducts that have a 1 1 stoichiometry of cations to electrons.The properties strongly point to ionization to yield alkali cations that interact with the Si—O—Si units that line the zeolite channels. Apparently, the released electrons occupy the open spaces of the channels, which have diameters of — 7 A. The electrons are strongly coupled to form nearly diamagnetic materials. These inorganic electrides are stable to at least 100°C. Potentially, zeolite-based systems... 

Here reactions (10) and (11) highlight the comparison that can be drawn between an electron trapped in a cavity defined by a tetrahedron of sodium cations in the sodalite cage, and an electron trapped within solvent cavities in liquid ammonia. Furthermore, the ability to prepare trapped electrons in zeolites, in stoichiometric or near stoichiometric amounts, has led to the description inorganic electrides [88, 90]. Together these ideas have been found to constitute a remarkably robust conceptual framework for rationalizing the properties of a wide range of metal-zeolite compounds [88], whose main strength lies in its ability to do so without recourse to detailed structural information, which is available in only a few cases. 

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