High-nuclearity heterometallic clusters with both an anion and a cation sandwiched by planar cluster units: synthesis, structure and properties

To develop high-nuclearity clusters as multi-functional materials, we prepared a new type of sandwich clusters using an anion-templated synthetic strategy. The reactions of (2R,3R)-2,3-dihydroxybutanedioyl-bis(salicylidene hydrazone) (H6L) with [Cu-2(OAc)(4)(H2O)(2)] in the presence of alkali metal halide (NaCl, NaBr, KCl or KBr) provided four high-nuclearity clusters [MCu18L6X(C5H5N)(15)(DMF)(3)]center dot 3DMF center dot 6H(2)O (M = Na and X = Cl (1); M = Na and X = Br (2); M = K and X = Cl (3); and M = K and X = Br (4)). They represent a new type of nanoscale high-nuclearity heterometallic sandwich clusters, in which the halide anion is fully sandwiched by two planar nonanuclear clusters, and the alkali metal ion is half-sandwiched on the top of the upper planar nonanuclear cluster. The experimental magnetic data and simulating results reveal dominant antiferromagnetic interactions between metal ions in these compounds. Their dielectric constants and electric hysteresis loops were also measured.