Formation of the m-dinitrobenzene radical-anion dimer in the triplet ground state on magnesium oxide

Abstract

The adsorbed state of m-dinitrobenzene on the surface of magnesium oxide has been studied by means of visible absorption and electron spin resonance spectroscopies. In the visible spectrum the adsorbed dinitrobenzene had two absorption maxima at 560 and 690 nm, attributed to the nitro radical anion and radical dimer, respectively. The adsorbed species showed an e.s.r. signal of Δm_s=±2 transitions characteristic of a triplet-state two-spin system in the g= 4 region, in addition to a monomer signal at g= 2. The number of radical dimers formed was sensitive to the conditions of preheating the oxide in air.