Synthesis and comparative structural study of 2-(pyridin-2-yl)-1H-perimidine and its mono- and di-N-methylated analogues

Abstract

The title compounds, 2-(pyridin-2-yl)-1H-perimidine (C16H11N3; 1), 1-methyl-2-(pyridin-2-yl)-1H-perimidine (C17H13N3; 2), and 1,3-dimethyl-2-(pyridin-2-yl)-1H-perimidinium iodide (C18H16N3+·I−; 3) were synthesized under mild conditions and their structures were determined by 1H NMR spectroscopy and single-crystal X-ray analysis. The N-methylation of the nitrogen atom(s) at the perimidine moiety results in a significant increase of the interplane angle between the pyridin-2-yl ring and the perimidine system. The unsubstituted perimidine (1) forms a weak intramolecular N—H...N bond that consolidates the molecular conformation. In the crystal structures of 1–3, the molecular entities all are assembled through π–π and C—H...π interactions.

Keywords

• crystal structure
• perimidine
• π–π stacking
• hydrogen-bonding
• nmr study