Triazole-Bridged Zinc Dinuclear Complexes: Mechanochemical Synthesis, Crystal Structure, and Biological Activity

[Image: see text] Two zinc (Zn) complexes, [Zn(2)(DAT)(2)Cl(4)] (I) and [Zn(2)(DAT)(2)(NO(3))(4)] (II), were prepared by grinding 3,5-diamino-1,2,4-triazole (C(2)H(5)N(5), DAT) with Zn precursors such as ZnCl(2) and Zn(NO(3))(2), respectively. This solid-state reaction gives the corresponding Zn complex as the sole product in over 99% yield. This mechanochemical method promotes the selective formation of Zn complexes different from those obtained using the conventional solution-based route. The crystal structures of the two complexes were analyzed by single-crystal X-ray diffraction. Complex (I) crystallizes in the monoclinic space group P2(1)/c, whereas complex (II) crystallizes in the triclinic space group P(1̅). Each complex is characterized by the presence of a characteristic DAT-bridged dimer with one DAT ligand per Zn atom, and the DAT ligand provides a bridge between the two Zn metals. All Zn centers of (I) and (II) adopted a slightly distorted tetrahedral geometry. Both complexes contain a hexanuclear Zn(2)N(4) ring, but their ring structures are different. Complex (I) possesses a boat geometry, while complex (II) has a nearly planar structure. The Zn-bound chlorides of complex (I) form intermolecular N–H···Cl hydrogen bonds that link neighboring molecules. In complex (II), the O atoms in the nitrate groups are hydrogen-bonded to the DAT ligand via O···H–N linkages. Both complexes exhibit blue emissions in the solid state at ambient temperature. They were evaluated as anticancer agents in HeLa, NCCIT, and MCF-7 cancer cell lines, exhibiting promising anticancer activities.