Isolation, crystal structure and DFT study of 2,2,6,6-tetramethyl-4-oxo-piperidinium nitrate isolated from the stembark of Vitex doniana (Lamiaceae)

We present the results of the analysis of 2,2,6,6-tetramethyl-4-oxo-piperidinium nitrate isolated from the stem bark of Vitex doniana, a tree growing in Nigeria. The low-temperature molecular structure comprises one 2,2,6,6-tetramethyl-4-oxopiperidinium cation and one nitrate anion as one molecule in the asymmetric unit. The compound crystallizes in the monoclinic space group P2₁/n. A portion of the nitrate anion exhibits positional disorder with the main disorder component present 66.253(2) % of the time and the minor disorder component present 33.279(2) % of the time. In comparison with the previously reported room-temperature structure of C₉H₁₈N₂O₄. The low-temperature structure shows similarity with the piperidinium ring adopting a slightly deformed chair conformation while the nitrate anion is disordered. DFT method was used to complement the experimental study.