Experimental and theoretical study on the enhanced antifungal activities of tebuconazole after complexation with two zinc salts

The frequent use of 1,2,4-triazole fungicide tebuconazole has led to serious resistance and environmental pollution. The synthesis of its metal complexes can not only enhance its activity but also solve the problems of resistance and residues. Two Zn(II) complexes of tebuconazole have been synthesized and characterized by elemental analysis, IR spectra and single-crystal X-ray diffraction. Crystal structures of the title complexes show that in complex 1, Zn(II) forms coordination bonds with four tebuconazole ligands and is additionally coordinated by two NO₃⁻ ions. In contrast, complex 2 involves the coordination of Zn(II) with two tebuconazole ligands and two CH₃COO⁻ ions. In addition, both the Zn(II) complexes exhibit stronger antifungal activities against four tested plant fungal pathogens than their ligand. Notably, complex 2 exhibits greater antifungal activity than complex 1 because of the different proportions of zinc salt to tebuconazole. Synergistic actions and DFT (the density functional theory) results supported the experimental antifungal results for enhancement in the activities of the complexes.