Magnetic properties of a bishelical [4 + 4 + 4] trinuclear copper(ii) complex

A peculiar [4 + 4 + 4] trinuclear Cu(II) bishelicate has been studied by X-ray diffraction techniques, FT–IR and UV–Vis spectroscopies, magnetic measurements and EPR spectroscopy. Magnetic susceptibility studies indicate a strong antiferromagnetic interaction (J/k = −194 K) between the three copper ions in the bishelicate. The existence of antiferromagnetic intermolecular interactions (z′J′/k = −0.91 K) was also determined. In spite of the presence of two magnetically different centres, only one signal is observed due to the exchange effects. Below 100 K the linewidth of the signals rapidly decreases and a typical exchange narrowed spectrum is observed at 4 K. The main contribution to the ground state wave function can be attributed to the dx2 − y2 orbitals, as expected for tetrahedrally distorted planar square Cu(II) chromophores.