DENSITY FUNCTIONAL THEORY STUDIES ON STABILITY OF ALKALINE METAL COMPLEXES OF PENTAZOLE AND OXOPENTAZOLE ANIONS

摘要

We performed calculations on the alkaline metal ion complexes of pentazole (N_5) and oxopentazole anions (ON_5~-) using density functional theory (DFT) methods in the gas phase and in solution to examine the stability of the complexes. Complexation energies and the Gibbs energies were estimated, and the structures corresponding to local and global minima are also reported. In addition, the transition structures along the decomposition pathways of the metal-complexed nitrogen clusters were characterized to evaluate the kinetic stability of the clusters in the gas phase and in solution. The barriers for the decomposition of metal coordinated oxopentazole were not altered compared to that for the bare oxopentazole anion in the gas phase, while the barriers were significantly reduced on complexation because the cation weakens the N-N bond length in the gas phase. This shows that the metal cation preferentially binds to the oxygen atom rather than to one of the nitrogen atoms in the ring. The kinetic stability of pentazole and oxopentazole was slightly increased in the THF solvent, and the metal cation did not alter the stability in solution because the M-N_5 or M-ON_5 structures were more relaxed than the corresponding structures in the gas phase.