STRUCTURE AND PROPERTIES OF LI-), AN ELECTRIDE WITH A 1D SPIN-LADDER-LIKE CAVITY-CHANNEL GEOMETRY((CRYPTAND[2.1.1])E()

The title electride crystallizes in the orthorhombic space group Pbcn with a = 10.060(4) Angstrom, b = 23.134(8) Angstrom, c = 8.380(4) Angs trom, and z = 4. A second powdered phase of unknown structure, but wit h rather different properties, forms when rapidly precipitated ''seed' ' powder is used. The crystalline phase contains electron-trapping cav ities, each of approximate diameter 4.3 Angstrom, connected in zigzag fashion along the c axis by rather open channels of minimum diameter 2 .4 Angstrom (center-to-center distance 7.9 Angstrom). Each cavity is a lso connected to next-neighbor cavities, 8.2 Angstrom away along c, by channels of diameter 1.5 Angstrom. Inter-chain channels are <1.0 Angs trom in diameter so that the cavity-channel structure is well-describe d as ''ladder-like''. Replacing the trapped electron by Na- in the cor responding sodide, Li+ (cryptand [2.1.1])Na-, results in an orthorhomb ic structure (space group Pna2(1)). Although the anionic sites in the sodide are only slightly bigger than those in the electride, the chann el structure is markedly different, forming a 3-dimensional network. T he magnetic susceptibilities of both phases of the electride above 14 K are well-fit by the linear chain Heisenberg antiferromagnetic model with values of J/k(B) of -54 (crystals) and -17.8 K (powder). Both typ es show marked deviations below 14 K toward greater spin-pairing. This behavior was verified by EPR measurements of intensity vs temperature . The electride was characterized further by two probe pressed pellet conductivity, variable temperature Li-7 MAS-NMR, and DSC.