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
摘要:
A novel tetranuclear copper(II) cluster of formula [Cu(C8H8N5O2)]4(NO3)4(H2O)8 is reported containing the anion of N,N'-imidopicolinyloxamylhydrazine as a dinucleating bis(didentate) ligand. The tetrahedral cluster has crystallographic S4 symmetry and is flattened along one of the C2 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) angstrom, alpha=beta=gamma=90-degrees, V=5703 angstrom3, 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) angstrom. 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) angstrom. 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.