Using Lewis acidity differences in chelating ligands to control molecular structure and supramolecular assembly of Cu(II) complexes

The electronic effects of the fluorine atoms in hfacac (hexafluoroacetylacetonato) compared with acac (acetylacetonato) in Cu(II) complexes are used to control the molecular and supramolecular structure of Cu(II) compounds. While bis(acac)Cu(II) (acac = acetylacetonato) is known to be able to have a fifth-position coordination, bis(hfacac)Cu(II), (hfacac = hexafluoroacetylacetonato) may have two extra ligands. This, together with the reliable “supramolecular reagent” isonicotinamide, as the additional ligand, are used to go from a zero-dimension structure, with Cu-acac, to an extended supramolecular two-dimension network, with Cu-hfacac. The molecular and crystal structure of bis(acetylacetonato-O,O′)-(isonicotinamide-N) copper(II), 1, and bis(hexafluoroacetylacetonato-O,O′)-trans-bis(isonicotinamide-N) copper(II), 2, are reported.