Field-induced slow magnetic relaxation in a new family of tetranuclear double-stranded Cu2II-Ln2III metallohelicates

Abstract

A series of tetranuclear Cu2IILn2III (LnIII from LaIII to YbIII), double-stranded metallohelicates have been synthesized using a bis-bidentate flexible ligand obtained by condensing o-vanillin with 4,4′-oxydianiline. The complexes exhibit a variety of LnIII environments and decreasing coordination number along the series and several nitrato coordination modes proved by the structural determination of the LaIII (1La), SmIII (4Sm), GdIII (5Gd), ErIII (9Er), and YbIII (10Yb) derivatives. The other members of the family (2Ce, 3Pr, 6Tb, 7Dy, and 8Ho) have been characterized by powder X-ray diffraction to verify their isostructurality. Susceptibility measurements show field-induced slow relaxation of the magnetization for the anisotropic TbIII and DyIII complexes and for the isotropic GdIII system.