Syntheses, crystal structures and intermolecular interactions of six novel pyrimidin-2-yl-substituted triaryltriazoles

Six new pyrimidin-2-yl-substituted triaryltriazoles, namely, 4-(4-R-phenyl)-3-(pyridin-2-yl)-5-(pyrimidin-2-yl)-1,2,4-triazoles [L¹: R = methoxy (OCH₃); L²: R = methyl (CH₃); L³: R = nil (H); L⁴: R = bromo (Br); L⁵: R = chloro (Cl); L⁶: R = fluoro (F)] have been successfully synthesized with yields in the range 68.3–81.7%. Compounds L^1–6 have been characterized by UV–Vis, FT–IR, ¹H NMR and ESI–MS spectroscopy, and elemental analysis. In addition, the structures of L^2–6 and the ethanol monosolvate of L² (L²·C₂H₅OH) have been determined by single-crystal X-ray diffraction. A combination of intermolecular O—H. . .N, C—H. . .O, C—H. . .N and C—H. . .π hydrogen bonds connects the components of L²·C₂H₅OH into a three-dimensional (3D) framework. A combination of three intermolecular C—H. . .N hydrogen bonds links the molecules of L² or L³ into two different 3D networks. Both L⁴ and L⁵ show a similar 3D net structure through two intermolecular C—H. . .N hydrogen bonds and one kind of C—H. . .π interaction. However, L⁶ displays a more complicated 3D net structure via three intermolecular C—H. . .N hydrogen bonds and one kind of C—H. . .π interaction. Notably, an interaction between the π-electrons and the lone-pair p-electrons of a halogen atom (Br, Cl and F) is observed in L^4–6, which will further stabilize the 3D networks. The intermolecular interactions in L²·C₂H₅OH and L^2–6 were further investigated by 3D Hirshfeld surface analyses and 2D fingerprint plots to show that the prominent interactions are H. . .H, N. . .H/H. . .N and C. . .H/H. . .C contacts.