| Summary: | The compounds [1,4′-bipyridine]-1,1′-diium [CuCl<sub>4</sub>] (<b>1</b>) and [1,4′-bipyridine]-1,1′-diium [CuBr<sub>4</sub>] (<b>2</b>) were prepared and their crystal structures and magnetic properties are reported. The compounds are isomorphous and crystallize in the monoclinic space group <i>C</i>2/c. The cation crystallizes in a two-fold disordered fashion with the terminal nitrogen and carbon atoms exhibiting 50% occupancies. This results in a crystal packing arrangement with significant hydrogen bonding that is very similar to that observed in the corresponding 4,4′-bipyridinediium complexes. Temperature dependent magnetic susceptibility measurements and room temperature EPR spectroscopy indicate the presence of very weak antiferromagnetic exchange. The data were fit to the Curie−Weiss law and yielded Weiss constants of −0.26(5) K (<b>1</b>) and −1.0(1) K (<b>2</b>).
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