Coordination of nitroxyl radical probes to the Lewis acid sites on the surface of gallium oxide: a quantum-chemical analysis

The results of ESR investigations and quantum-chemical studies on the coord ination of 2,2,6.6-tetramethylpiperidine-N-oxyl to the Lewis acid sites (LA S) on the surface of gallium oxide are reported and analyzed. The structura l, spin, electrostatic, and energy characteristics of the coordination of t he simplest nitroxyl radical, H2NO., to the Ga(OH)(3) model cluster-type LA S were calculated by the unrestricted Hartree-Fock method in the 6-31G basi s set and using the semiempirical PM3 approximation. The properties of gall ium-containing nitroxyl surface complexes and their aluminum-containing ana logs are compared. According to the results of cluster quantum-chemical cal culations, the LAS on the surface of gallium oxide are stronger than those on the alumina surface.