Enhanced antifungal activities of four Zn(II) complexes based on uniconazole: Enhanced Antifungal Activities of Zn(II) Complexes with Uniconazole

Four Zn(II) complexes, [ZnL2(SO4)](n) (1), [ZnL4(H2O)(2)]center dot 2(NO3)center dot 4EtOH (2), [ZnL2Cl2]center dot L (3), and [ZnL2Br2]center dot L (4) (L=uniconazole), were synthesized using a hydrothermal method and characterized by elemental analysis, FT-IR spectroscopy, and single-crystal XRD. Complex 1 formed a one-dimensional polymer chain. However, complexes 2-4 were obtained as zero-dimensional mononuclear coordination compounds. The antifungal activities of these complexes were then evaluated against four selected fungi using the mycelial growth rate method. The resulting data indicate that all complexes show better antifungal activities than their ligands and mixtures. In addition, the interactions between the metal salts of complexes 1-4 and uniconazole seem to be synergistic. Furthermore, the polymer chain structure of complex 1 significantly enhanced the bioactivity, especially against Botryosphaeria ribis (I). Density functional theory (DFT) calculations were carried out to help explain the enhanced bioactivity after the formation of Zn(II) complexes. The resulting data show that the HOMO-LUMO energy gaps of complexes 1-4 (0.0578, 0.0946, 0.1053, and 0.1245eV) are smaller than that of the free ligand (0.1247eV) and correlate with the antifungal activity of the zinc complexes.