Collect. Czech. Chem. Commun. 1982, 47, 1282-1289

Quantum chemical study of physical characteristics of Co- and Ni-faujasites

Stanislav Beran

The J. Heyrovský Institute of Physical Chemistry and Electrochemistry, Czechoslovak Academy of Sciences, 121 38 Prague 2


The CNDO/2 method was used for a physico-chemical characterization of faujasite zeolites, modelled by T6O6(OH)12 clusters containing Ni+, Ni2+, Ni(OH)+, Co2+, Co3+, Co(OH)+ cations localized in the SII and SI' cationic positions. It is shown that the cations are bound preferentially to the oxygen atoms of the zeolite skeleton by a strong electron donor-acceptor bond. As the consequence of the bond formation, the electron charge is significantly shifted from a skeleton to the cation. The charge densities calculated on the cations (Ni+ ~ 0.3, Ni2+ ~ 0.35, Co2+ ~ 0.4, Co3+ ~ 1.1 respectively) show that with uni- and bivalent cations the positive charge is in main part compensated by donation of electrons from the skeleton, while with trivalent cations the compensation is only partial. The Ni+ cation possesses significant electron donor properties whereas the Co3+ cation has a strong electron acceptor character. For both cations bivalency appears to be the most stable valent state. Both studied cations show great affinity to hydratation, however, their corresponding hydroxyl adducts - the Ni(OH)+ and Co(OH)+ cations exhibit substantially less acid properties, compared with the hydroxyl groups of the skeleton.