Electron spin resonance spectral study of exchange coupling in the copper(II) chelate of 2,5-diethoxalylcyclopentanone

Abstract

X-band e.s.r. spectral measurements have been made on the β-triketone–copper(II) chelate of 2,5-diethoxalylcyclopentanone in various solvent systems at room temperature and 77 K. The findings support the conclusion that dimeric species are formed in which exchange coupling takes place. In dimethylformamide the introduction of zinc(II) results in the replacement of copper(II) in the copper(II) pairs which leads to the formation of a hetero-metal ion chelate. In trimethyl phosphate the same process leads to a novel species involving both copper(II) and zinc(II) ions in which exchange coupling persists between the copper(II)–copper(II) pairs. All the results involving dimer formation are analysed by comparison of a theoretical computer simulated curve with the experimental result, and the zero field splitting parameter, D, is evaluated. The parameter D involves contributions from both exchange and dipole–dipole coupling in these cases.