INTERACTION OF NITROBENZENE WITH MGO SURFACE BY TEMPERATURE-PROGRAMMED DESORPTION AND ESR SPECTROSCOPY

The adsorption of nitrobenzene on the surface of magnesium oxide has b een studied by TPD and ESR methods. The high temperature activation of MgO reveals the presence of low coordinated oxygen ions (LC), which a re the one-electron donor (reducing) sites of MgO surface, resulting i n the formation of different nitrobenzene anion radicals. The corner O -3C(2-) and probably the edge O-4C(2-) lattice ions are the source of single electrons to the adsorbed nitrobenzene molecules. Depending on adsorption temperature and surface coverage, there are visible at leas t three forms of NE radicals in ESR spectra with different values of t he hyperfine splitting (A(parallel to)(N)). These forms differ in ther mal stability. The small variations of particular A(parallel to)(N) va lue was attributed to the different chemical environment of the low co ordinated adsorption sites on MgO surface.