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

The title compounds, 2-(pyridin-2-yl)-1H-perimidine (C(16)H(11)N(3); 1), 1-methyl-2-(pyridin-2-yl)-1H-perimidine (C(17)H(13)N(3); 2), and 1,3-dimethyl-2-(pyridin-2-yl)-1H-perimidinium iodide (C(18)H(16)N(3) (+)·I(−); 3) were synthesized under mild conditions and their structures were determined by (1)H 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.