Abnormal conformation change of an asymmetrical triaryltriazole before and after its coordination

A new asymmetrical substituted triaryltriazole ligand, 3-(p-methoxyphenyl)- 4-(p-bromophenyl)-5-(2-pyridyl)-1,2,4-triazole (L) and its complexes, trans-[MnL₂(NCS)₂] (1) and trans-[CuL₂(ClO ₄)₂] (2), have been successfully synthesized and characterized by UV, IR, ESI-MS, elemental analyses and single-crystal X-ray diffraction methods. In the structure, two L ligands are mainly stabilized by two kinds of intermolecular π⋯π interactions. In the complexes, each L ligand involves a chelating bidentate coordination mode via N atom of pyridyl group and one N atom of the triazole. Both complexes show a distorted octahedron containing two trans-coordinated anions in 1 with NCS^- but in 2 with ClO4-. The dihedral angle between the pyridyl and triazole ring in the free L ligand, 1 and 2 is 0.8(2)°, 12.8(2)° and 9.3(2)°, respectively, which represents the first example that the triazole-pyridyl twist angle in the complexes of any triaryltriazole is larger than that in the free L ligand.