Computational spectroscopy and DFT investigations into nitrogen and oxygen bond breaking and bond making processes in model deNOx and deN2O reactions

Molecular DFT modeling combined with computational spectroscopy (EPR and IR) were applied for analysis of the NO bond breaking and NN and OO bond making in the context of deNOx and deN2O reactions. Interaction of NO, N2O and NO2 with cationic (transition metals) and anionic (surface O2− ions) centers was explored at the molecular level. The elementary events such as reactant coordination, charge and spin redistributions, which are principal molecular constraints for efficient decomposition of the nitrogen oxides (N2O and NO) were discussed. Particular attention was paid to dynamics of the NO bond cleavage in N2O molecule through electron and oxygen atom transfer routes, evaluation of preferable coordination modes of NO, discrimination between inner- and outer-sphere mechanism of NN bond formation, and the influence of spin and electronic redistribution on the reaction course (spin catalysis). Owing to their simplicity and well known surface chemistry, model systems selected for studies of such processes include MoOx/SiO2, MgO and ZSM-5 zeolite exchanged with various transition metal ions (TMI) of different electron configuration and spin multiplicity: Mo5+ (d1, 2D) Fe3+, Mn2+, Cr+ (d5, 6S), Fe2+ (d6, 5D), Co2+ (d7, 4F), Ni2+ (d8, 3F), Cu2+ (d9, 2D) and Cu+, Zn2+ (d10, 1S).