Magnetic moments of copper(II) complexes

Magnetic moments of octahedral, tetrahedral, square planar, trigonal planar, and trigonal pyramidal Cu(II) complexes have been discussed theoretically including the orbital contribution on the basis of the molecular orbital theory. It has been shown that the orbital contribution of electrons to the magnetic moment is expected only in tetrahedral, trigonal planar, and trigonal pyramidal complexes. The effective magnetic moment of tetrahedral Cu(II) complexes has been estimated to be about 2.2 at room temperature and that of tri-coordinated Cu(II) complexes to be higher than the spin-only value. The hypothesis of electron promotion to a 4p level in Cu(II) complexes has been criticized.