A density functional theory investigation of degradation of Nitroguanidine in the photoactivated triplet state.

It is well known that nitroguanidine (NQ) undergoes photodegradation when exposed to UV-radiation. However, the mechanism of NQ photolysis is not fully understood. Earlier investigations have shown that nitrocompounds undergo to their triplet state population through crossing of electronic singlet and triplet excited state potential energy surfaces due to the nitrogroup rotation and nonplanarity under electronic excitation. Therefore, it is expected that under electronic excitation, the presence of nitrogroup in NQ would also lead to the population of electronic lowest energy triplet state. To shed a light on the degradation of NQ in alkaline solution under electronic excitation, we performed a detailed investigation of a possible degradation mechanism at the IEFPCM/B3LYP/6-311++G(d,p) level in the electronic lowest energy triplet state. We found that degradation ability of NQ in the electronic triplet state would be significantly larger than in the electronic ground singlet state. It was revealed that the photodecomposition of nitroguanidine might occur through several pathways involving N-N and C-N bond ruptures, nitrite elimination, and hydroxide ion attachment. Nitrogen of nitrogroup would be released in the form of nitrite and nitrogen (I) oxide. Computationally predicted intermediates and products of nitroguanidine photolysis such as nitrite, hydroxyguanidine, cyanamide, and urea correspond to experimentally observed species.