distorted square-planar. The inhibitory activities of all the obtained complexes were tested in vitro against jack bean urease. It was found that Schiff base copper(II) complexes 1, 3, 5, 8 and 11 showed strong urease inhibitory activities (IC50 = 1.51–3.52 μM) compared with acetohydroxamic acid (IC50 = 62.52 μM), which was a positive reference. Their structure–activity relationships were further discussed