Detection of pentazolate anion (cyclo-N5−) from laser ionization and decomposition of solid p-dimethylaminophenylpentazole

Laser desorption ionization (LDI) time-of-flight (TOF) mass spectroscopy of solid p-dimethylaminophenylpentazole (1) gives strong peaks of m/z −42 and −70. The −70 peak was identified by 15N labeling of 1 to be the pentazolate anion (cyclo-N5−). The pentazolate anion is formed by an electron attachment to 1 forming the corresponding radical anion followed by a decomposition into 4-N(CH3)2-C6H4 and (cyclo-N5−). The LDI TOF experimental study also revealed that the (cyclo-N5−) is very stable. These conclusions are supported by QM calculations at the B3LYP/6-311+G(2df,p) level.