Synthesis, crystal structures and luminescence properties of seven mononuclear zinc(II), cadmium(II), cobalt(II) and nickel(II) complexes with 5-(4-methylphenyl)-3-(pyridin-2-yl)-1H-1,2,4-triazole.

Due to their versatile coordination modes and metal-binding conformations, triazolyl ligands can provide a wide range of possibilities for the construction of supramolecular structures. Seven mononuclear transition metal complexes with different structural forms, namely aquabis[3-(4-methylphenyl)-5-(pyridin-2-yl)-1H-1,2,4-triazolato-κ ² N ¹ ,N ⁵ ]zinc(II), [Zn(C ₁₄ H ₁₁ N ₄ ) ₂ (H ₂ O)], (I), bis[5-(4-methylphenyl)-3-(pyridin-2-yl)-1H-1,2,4-triazole-κ ² N ³ ,N ⁴ ]bis(nitrato-κO)zinc(II), [Zn(NO ₃ ) ₂ (C ₁₄ H ₁₂ N ₄ ) ₂ ], (II), bis(methanol-κO)bis[3-(4-methylphenyl)-5-(pyridin-2-yl)-1H-1,2,4-triazolato-κ ² N ¹ ,N ⁵ ]zinc(II), [Zn(C ₁₄ H ₁₁ N ₄ ) ₂ (CH ₄ O) ₂ ], (III), diiodidobis[5-(4-methylphenyl)-3-(pyridin-2-yl)-1H-1,2,4-triazole-κ ² N ³ ,N ⁴ ]cadmium(II), [CdI ₂ (C ₁₄ H ₁₂ N ₄ ) ₂ ], (IV), bis[5-(4-methylphenyl)-3-(pyridin-2-yl)-1H-1,2,4-triazole-κ ² N ³ ,N ⁴ ]bis(nitrato-κO)cadmium(II), [Cd(NO ₃ ) ₂ (C ₁₄ H ₁₂ N ₄ ) ₂ ], (V), aquabis[3-(4-methylphenyl)-5-(pyridin-2-yl)-1H-1,2,4-triazolato-κ ² N ¹ ,N ⁵ ]cobalt(II), [Co(C ₁₄ H ₁₁ N ₄ ) ₂ (H ₂ O)], (VI), and diaquabis[3-(4-methylphenyl)-5-(pyridin-2-yl)-1H-1,2,4-triazolato-κ ² N ¹ ,N ⁵ ]nickel(II), [Ni(C ₁₄ H ₁₁ N ₄ ) ₂ (H ₂ O) ₂ ], (VII), have been prepared by the reaction of transition metal salts (Zn ^II , Cd ^II , Co ^II and Ni ^II ) with 3-(4-methylphenyl)-5-(pyridin-2-yl)-1H-1,2,4-triazole (pymphtzH) under either ambient or hydrothermal conditions. These compounds have been characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction. All the complexes form three-dimensional supramolecular structures through hydrogen bonds or through π-π stacking interactions between the centroids of the pyridyl or arene rings. The pymphtzH and pymphtz ^- entities act as bidentate coordinating ligands in each structure. Moreover, all the pyridyl N atoms are coordinated to metal atoms (Zn, Cd, Co or Ni). The N atom in the 4-position of the triazole group is coordinated to the Zn and Cd atoms in the crystal structures of (II), (IV) and (V), while the N atom in the 1-position of the triazolate group is coordinated to the Zn, Co and Ni atoms in (I), (III), (VI) and (VII).