A novel tetranuclear copper(II) cluster containing twisted hydrazide bridges. X-ray crystal structure and magnetic properties of tetrakis[ N,N′-imidopicolinyloxamylhydrazine)copper(II)] tetranitrate octahydrate

Abstract

A novel tetranuclear copper(II) cluster of formula [Cu(C 8H 8N 5O 2)] 4(NO 3) 4(H 2O) 8 is reported containing the anion of N,N′-imidopicolinyloxamylhydrazine as a dinucleating bis(didentate) ligand. The tetrahedral cluster has crystallographic S 4 symmetry and is flattened along one of the C 2 axes. The copper(II) ions are located on its vertices. The title compound crystallizes in the tetragonal space group I4 1/ a, a=19.334(4), c=15.257(13) Å, α=β=γ90°, V=5703 Å 3, Z=4 (tetranuclear units). Each copper(II) is in a distorted square pyramidal environment consisting of three nitrogen atoms and one oxygen atom from the ligand, and an apical oxygen from a nitrate at 2.01(2) Å. Some relevant interatomic distances are CuN=1.95(1), CuO=1.96(1), CuCu′CuCu″=4.456(4), CuCu‴=3.435(4) Å. The X-band powder EPR spectra at 298 and 77 K show an isotropic signal at g=2.09. The magnetic susceptibility measurements (6.5–280 K) indicate that there is no significant magnetic interaction between the metal ions; this behaviour can be understood on the basis of orthogonal magnetic orbitals within the cluster.