Synthesis, structure, and magnetism of two tetrahalocuprate salts: (5-TFAPH)2CuX4 (5-TFAP=2-amino-5-trifluoromethylpyridine, X=Cl, Br)

Abstract: Reaction of 2-amino-5-trifluoromethylpyridine (5TFAP) with copper halides in aqueous acid gives rise to the salts (5TFAPH)2CuX4 [X=Cl (1), Br (2)] which were characterized by IR, combustion analysis, single-crystal X-ray diffraction and variable temperature magnetic susceptibility. The complexes crystallize in the triclinic space group , but are not isostructural. The chloride salt 1 forms an S=½ magnetic ladder via a combination of bihalide (rungs) and two-halide (rails) bridges. The ladders are well isolated by the 5TFAPH cations. A fit of the magnetic susceptibility data (T =1.8–310K) agreed well with the strong-rung ladder model, yielding C=0.384(4)emu-K/mol-Oe, J rung =−13.9(1)K and J rail =−2.90(4)K. Compound 2 exhibits tetrabromocuprate ions which are bridged into a distorted honeycomb structure, but with short Br…Br contacts between the layers. Magnetic data indicate only very weak antiferromagnetic exchange in spite of Br…Br contacts as short as 3.8Å. [Copyright &y& Elsevier]