Persistent C–I⋯π halogen-bonded layer motifs involving 4-iodobenzoate paddlewheel units, Cu2(4-Ibz)4(L)2

Abstract

The Cu2(4-Ibz)4 paddlewheel unit (4-Ibz = 4-iodobenzoate) has been synthesised with a series of monodentate axial ligands, L = acetone, DMSO, EtOH, DMF, giving Cu2(4-Ibz)4(L)2, or with linear ditopic ligands, L2 = dabco, 4,4-bipyridine, giving Cu2(4-Ibz)4(L2). The crystal structures of these compounds form persistent layer structures which are propagated in the four orthogonal directions of the iodobenzoate ligands around each paddlewheel unit via a combination of halogen bonds and offset π-stacking arrangements. Halogen bonds are either C–I⋯π or C–I⋯I interactions. The axial ligands are coordinated orthogonal to the layers and either fill spaces in the layers above and below (monodentate ligands, L) or link layers together (ditopic ligands, L2). Only in the case of the longest ditopic ligand used, 4,4′-bipyridylethane, does the paddlewheel fail to form.