Ordering of Cu(II) ions in supported copper-titanium oxide catalysts

Two types of ESR spectrum (A and B) of exchange-coupled Cu²⁺ ions have been found for Cu-Ti-O catalysts at 77 K and 300 K. In associates A and B, the Cu²⁺ ions form a system with orbital ordering. The difference between the spectra is due to the difference between the ground states of adjacent Cu²⁺ ions in the associates: the ground states are $d_{x^2 } $ and $d_{y^2 } $ for A type associates and $d_{x^2 - y^2 } $ and $d_{z^2 - x^2 } $ for B type associates. The copper associates lie on the surface of the TiO₂ (anatase) support microparticles.