High-density electron anions in a nanoporous single crystal:: [Ca24Al28O64]4+(4e-)

We removed similar to100% of clathrated oxygen ions from the crystallographic cages in a single crystal of 12CaO.7Al(2)O(3), leading to the formation of high-density (similar to2x10(21) cm(-3)) electrons highly localized in the cages. The resulting electron forms a structure that we interpret as an F+ center and migrates throughout the crystal by hopping to a neighboring cage with conductivity similar to100 siemens per centimeter, demonstrating that the encaged electron behaves as an anion. The electron anions couple antiferromagnetically with each other, forming a diamagnetic pair or singlet bipolaron. The resulting [Ca24Al28O64](4+)(4e(-)) may be regarded as a thermally and chemically stable single crystalline "electride."