Magnetism of self-assembled mono- and tetranuclear supramolecular complexes

Abstract

The magnetization of a novel supramolecular grid structure consisting of four bis(bipyridyl)-pyrimidine ligands and four (Formula presented) ions and that of the mononuclear analogue (Formula presented) was measured. Magnetic anisotropy was determined from investigations of powder as well as of crystal samples. We provide evidence for an intramolecular antiferromagnetic coupling of the four (Formula presented) spins of the tetranuclear species with (Formula presented) The magnetization of the mononuclear complex is typical for a (Formula presented) spin with zero field splitting. The magnetization of the tetranuclear grid is discussed in terms of the effective spin Hamiltonian appropriate for (Formula presented) ions including various higher order exchange terms. In particular, significant indications for a biquadratic term of about (Formula presented) is found. © 1998 The American Physical Society.