Aminotetrazine–argon, the world's smallest ‘large gas-phase cluster’

Abstract

The photodissociation dynamics of the complexes aminotetrazine–Ar and aminotetrazine–Ar₂ have been studied using supersonic jet spectroscopy. The lowest excited electronic state of aminotetrazine was found to have a much longer fluorescence lifetime (154 ns in the vibrationless level) than tetrazine (0.9 ns), and the photodissociation reaction could be followed for a much longer time than was the case with tetrazine. It was found that the photodissociation rate varied dramatically depending on the initially excited vibronic state. Excitation of the 16b² level of aminotetrazine–Ar at U_o+ 446 cm^–1 produced complete dissociation during the fluorescence lifetime, while excitation of the 6a¹ level at U_o+ 606 cm^–1 produced very little dissociation. Thus, this simple complex could store considerable excess energy for more than a microsecond without dissociating. The photodissociation rates of the complex aminotetrazine–Ar₂ also depended strongly on the initially excited state. Moreover, the dissociation product branching ratio of aminotetrazine–Ar₂ between the aminotetrazine–Ar and the free aminotetrazine photoproducts also varied greatly from state to state.