Two novel Co(II) and Ni( II) complexes of tebuconazole with enhanced antifungal activities

Two transition metal complexes, [CoL4Cl2] . 4MeOH 1 and [NiL4Cl2] . 4MeOH 2 (L = (RS)-1-(4-chlorophenyl)-4,4-dimethyl-3-(1,2,4-riazole-1-ylmethyl) pentane-3-ol), tebuconazole were synthesized and their structures were determined using single crystal X-ray diffraction (XRD). Crystal structural analysis shows that complexes 1 and 2 have similar structures, both with the metal cation lying on a crystallographic inversion center and coordinated with four triazole groups and two chloride anions. The antifungal activities of L and its complexes against four selected plant pathogenic fungi were evaluated. The results show that both complexes have stronger bioactivities than the ligand L and that complex 2 has slightly higher bioactivities than complex 1. To elucidate the mechanisms behind the increased antifungal activities of the title complexes in comparison with L, cumulative release studies in static water and theoretical investigations of the complexes were carried out. The results indicate that there are three factors contributing to the enhanced bioactivities: attractive controlled release properties, synergic interaction between metal cations and L, and improved penetration into the lipid membranes.