Magnetostructural studies of copper(ii)–verdazyl radical complexes

Abstract

The synthesis, structures, and magnetic properties of several Cu(II) complexes of verdazyl radicals are presented. Reactions of chelating verdazyl radicals with either CuCl₂·2H₂O or Cu(hfac)₂·2H₂O produced 1 ∶ 1 Cu ∶ verdazyl complexes with either chloride or hfac ancillary ligands. Structural characterization reveals that the CuCl₂ complexes of N,N′-dimethyl-3-(2-pyridyl)-6-oxoverdazyl or N,N′-bis(isopropyl)-3-(2-pyridyl)-6-oxoverdazyl have pseudo-square pyramidal copper ions with verdazyl rings bound in equatorial positions, while the Cu(hfac)₂ complex of N,N′-dimethyl-3-(N-methyl-2-imidazolyl)-6-oxoverdazyl is Jahn–Teller distorted pseudo-octahedral and has the verdazyl nitrogen axially bound. Variable temperature magnetic susceptibility studies reveal that equatorially bound verdazyls are strongly antiferromagnetically coupled, while the axially bound radicals are weakly ferromagnetically coupled. Intermolecular magnetic interactions are also an important component of the overall magnetism in these systems.