Magnetic susceptibility and the structure of Tri-coordinated copper(II) Complexes

Abstract

The magnetic susceptibilities of 2-hydroxynaphthaldehyde-(1)-[2-hydroxyanil] Cu(II), 5-nitrosalicylalanthranilic acid Cu(II), 5-bromosalicylalanthranilic acid Cu(II), 2-hydroxyformazylbenzene Cu(II), and 2-oarboxyformazylbenzene Cu(II), as well as their monopyridino-compounds, have been measured by the Gouy method at 25 °C. From the data of magnetic susceptibility, the effective magnetic moments were calculated per one copper atom in these chelates. Some of the pyridine-free complexes show magnetic moments that are smaller than the theoretical moment, 1.73 B.M., for one odd electron, while others have normal magnetic moments. Taking into account four other tri-coordinated copper chelates reported in a preceding paper, two alternative suggestions were made as follows. First, the subnormal moments resulting from the close distance of approach of two copper atoms in dimer molecules can be correlated with the planar configuration of chelate rings involving a copper atom. On the other hand, when a three-dimensional ring exists, the approach of two copper atoms to such a small distance as to cause an appreciable exchange effect is hindered by steric effects, resulting in the normal magnetic moment for this type of tri-coordinated complexes. Secondly, those pyridine-free tri-coordinated copper complexes showing normal moments have a carbonyl group, the oxygen atom of which may take part in the coordination about a copper atom.