Theoretical studies of the chemiluminescence reactions; luminol

Abstract: The vast majority of chemical reactions occurs only in the ground state, however photochemical reactions like chemiluminescence take place in ground and excited states. In almost all chemiluminescence processes oxygen-oxygen bond breakage is involved. But, there is no general reason to explain why these processes occur via an oxygen-oxygen cleavage. These types of phenomena are usually highly exothermic. Computational chemistry has risen as a powerful tool to characterize and analyze chemical phenomena. Quantum mechanics are utilized to explain chemical observations. Applying these equations, one can compute the chemical properties of any system in any state. In the present study, three chemiluminescence reactions derived from luminol are modeled; nitrogen based, oxygen based and dianion nitrogen based models. The key factor of oxygen-oxygen bond rupture is discussed and rationalized. The electronic potential energy surfaces of the three compounds are computed at complete active space self-consistent field theory. Peroxide compounds compared to the dinitrogenated  compounds show a lower activation energy and they are more exothermic. This study allows us to rationalize why luminol needs to be presented in a basic medium and oxidized in order to produce chemiluminescence.