Electrides: Ionic Salts with Electrons as the Anions

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Science  09 Feb 1990:
Vol. 247, Issue 4943, pp. 663-668
DOI: 10.1126/science.247.4943.663


Electrides are ionic compounds that have alkali metal cations complexed by a crown ether or cryptand, with trapped electrons as counterions. The crystal structures and properties of two electrides illustrate the diversity that is encountered. One Cs+ (18-crown-6)ze-, has relatively isolated, trapped electrons apparently centered at each anionic site. It has a low conductivity consistent with electron localization, with an activation energy for conductivity of at least 0.45 electron volt. The other, K+ (cryptand[2.2.2])e-, has electron pairs trapped in an elongated cavity in a singlet ground state, but there is also a thermally accessible paramagnetic state available. This electride is much more conducting, with an activation energy of only 0.02 electron volt.

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