Abstract On the basis of infrared spectroscopy and X-ray powder patterns, it is shown that 5-chlorosalicylalsalicylamine and its copper(II) salt are different from salicylal-5-chlorosalicylamine and its copper(II) salt, respectively, in the crystalline state. The nuclear magnetic resonance studies on salicylalsalicylamine and related compounds in solutions show that the double bond in the –CH=N–CH2- portion of these molecules is localized, i. e., the prototropic rearrangement of hydrogen atoms does not take place. Therefore, salicylalsalicylamine-copper(II) presents an example of a new type of three-coordinated copper (II) complexes showing a subnormal magnetic moment in spite of having ligands of a three-dimensional structure. This provides an additional evidence in favor of a presumption made by the present writers on the structure of three-coordinated copper(II) complexes showing a normal magnetic moment.