Superexchange in copper acetates

It was demonstrated in the preceding papers that the antiferromagnetic exchange coupling in a binuclear cobalt carboxylate is dominated by a superexchange mechanism via the carboxylate n bonds. In the present paper it is argued th at a similar process can account for all ground state properties of the structurally analogous, copper acetate molecule. The magnitudes, temperature-dependences and orientations of the principal magnetic susceptibilities can all be reproduced within this superexchange model. The g-values and zero-field splitting, previously considered to demonstrate the presence of a weak 8 bond between the copper atoms, have been shown to furnish no proof whatever of any particular coupling mechanism, provided there is an(x2 - y2 ground state for the copper atoms. The superexchange mechanism proposed is made possible essentially not via spin-orbit mixing of {xy) and (x2y2) — states but via configurational mixing of such functions caused by the close proximity of the second metal atom.