2026/06/08 by Andrew J. Peloquin, Colin D. McMillen, William T. Pennington · 1 voice
Chemistry · Engineering · #Crystallography and molecular interactions #Energetic Materials and Combustion #Click Chemistry and Applications
paper · doi:10.1107/s2053229626005814
openalex publication_date 2026/06/08 · openalex created_date 2026/06/17 · openalex updated_date 2026/07/23
Seven new crystal structures of 3,6-bis(pyridin-2-yl)-1,2,4,5-tetrazine (2-bptz) and 3,6-bis(pyridin-4-yl)-1,2,4,5-tetrazine (4-bptz) were determined with inorganic halogen donors (I 2 or I 3 − ), organic halogen donors [1,4-diiodotetrafluroobenzene ( p -F 4 DIB) or 1,3,5-trifluoro-2,4,6-triiodobenzene (1,3,5-TFTIB)], and the hydrogen-bond donor hydroquinone to investigate how pyridyl orientation and donor type influence supramolecular assembly. Structures formed with molecular iodine, namely, 2,2′-(1,2,4,5-tetrazine-3,6-diyl)dipyridinium bis(triiodide)–3,6-bis(pyridin-2-yl)-1,2,4,5-tetrazine–diiodine (1/1/1), C 12 H 10 N 6 2+ ·2I 3 − ·C 12 H 8 N 6 ·I 2 ( 1 ), and 4-[6-(pyridin-4-yl)-1,2,4,5-tetrazin-3-yl]pyridinium pentaiodide, C 12 H 9 N 6 + ·I 5 − ( 2 ), are dominated by N—H...N hydrogen bonding, with pyridine protonation yielding distinct packing arrangements: 2-bptz forms stacked triads along the a axis, whereas 4-bptz assembles into chains of [H(4-bptz)] + cations alternating with pentaiodide layers. Replacement of iodine with organoiodines in 3,6-bis(pyridin-2-yl)-1,2,4,5-tetrazine–1,4-diiodotetrafluorobenzene (1/1), C 6 F 4 I 2 ·C 12 H 8 N 6 ( 3 ), 3,6-bis(pyridin-4-yl)-1,2,4,5-tetrazine–1,4-diiodotetrafluorobenzene (1/1), C 6 F 4 I 2 ·C 12 H 8 N 6 ( 4 ), and 3,6-bis(pyridin-2-yl)-1,2,4,5-tetrazine–1,3,5-trifluoro-2,4,6-triiodobenzene (1/2), C 6 H 4 N 3 ·C 6 F 3 I 3 ( 5 ), shifts the primary interactions to C—I...N halogen bonding, producing one-dimensional staggered chains in 2-bptz and linear motifs in 4-bptz, with bifurcated C—I...N interactions in 5 involving both pyridine and tetrazine N atoms. Halogen–halogen and halogen–fluorine interactions further modulate packing and stacking orientations. Reactions with hydroquinone in 3,6-bis(pyridin-2-yl)-1,2,4,5-tetrazine–hydroquinine (2/1), 2C 12 H 8 N 6 ·C 6 H 6 O 2 ( 6 ), and 3,6-bis(pyridin-4-yl)-1,2,4,5-tetrazine–hydroquinine (1/1), C 12 H 8 N 6 ·C 6 H 6 O 2 ( 7 ), reveal the role of hydrogen bonding in long-range organization: 2-bptz forms discrete triads, whereas 4-bptz generates extended chains propagating through pyridine–phenol interactions. Pyridine-to-tetrazine plane-to-plane angles vary across structures, reflecting the influence of substitution pattern and donor type on molecular geometry. These results demonstrate that subtle changes in pyridyl orientation and the nature of halogen- or hydrogen-bond donors can direct the formation of distinct supramolecular architectures, providing a foundation for the rational design of tetrazine-based crystalline materials with tunable packing and noncovalent interactions.