Electron Spin Resonance in Transition Metal Chelates. II. Copper(II) Bis-Salicylaldehyde-Imine

Abstract

The electron spin resonance at 3.2 cm has been observed for single crystals of copper(II) bis‐salicylaldehyde‐imine diluted to ½ mole percent with the corresponding nickel chelate. Analysis of the spectrum by methods given in the preceding article indicate that the sigma bonding and in‐plane II‐bonding are appreciably covalent, whereas the out‐of‐plane π bonding is ionic. Hyperfine interactions in addition to that resulting from the copper nucleus were observed and shown to be attributable to interactions with the nitrogen nuclei adjacent to the copper ion and with the two protons bonded to the carbon atoms directly adjacent to the nitrogen atoms. The two protons bonded directly to the nitrogen atoms do not contribute to the hyperfine interactions. Bonding information obtained from the magnitude of the hyperfine interaction due to the nitrogen nucleus agrees with that obtained from the g tensor and hyperfine interaction of the copper nucleus. In addition structural information about nickel(II) bis‐salicylaldehyde‐imine is obtained. The Ni‐O distance is 1.92±0.07 A while the Ni‐N distance is 1.94±0.05 A. The angle between these bonds is found to be 93±3°.