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.