Choice of hydrogen bonds or halogen bonds by 2-halogenated 5-morpholinomethylphenyl triazolo[1,5-a]pyridine

The crystal structures of halogenated 1,2,4-triazolo[1,5-a]pyridine derivatives disclose intriguing structural chemistry features dictated by the formation of either hydrogen bonds (HBs) or halogen bonds (XBs). 2-Chloride and bromide derivatives (1 and 2) favor HBs, promoting the formation of bent-shaped conformers. The 2-iodide compound (3) favors XBs, leading to different shaped conformers split into polymorphic forms. The XB-mediated crystals (3I and 3II) are more thermodynamically stable than the HB-mediated crystals of 1 and 2.