Effect of halogen displacements on the exchange coupling in methyloxo-bridged binuclear copper (II) complexes: a density functional study

Effect of halogen displacements on magnetic coupling for methyloxo-bridged copper(II) dimers is investigated by means of DFT-BS (broken-symmetry) approach. Both coupling constants J and bridging O atomic charges(QO) increase with the increasing displacement degree n. The displacements lead to β electron transfer from Cl to Cu atoms, α electron from O atoms to methyl groups, which brings down spin densities on Cu2O2 core and further spread them toward the periphery of the models. The resulted spin delocalization reduces antiferromagnetic coupling strength for methyloxo-bridged copper (II) dimers. Furthermore, the decrease of spin densities on O px, O py and Cu dxy orbitals is the leading reason for the reduction of coupling strength as halogen displacements.