The Ligand Field Spectra of Copper(II) Complexes

A practical exercise for introducing students to ligand field spectra and the spectrochemical series, through the study of copper(II) species, is presented. Incorporated in the exercise is the preparation of a simple coordination compound: diaquabis(ethylenediamine)copper(II) iodide. The position of maximum absorbance (lambda max ) for each of the spectra can be used to compare the field strengths of O- and N-donor ligands. The value of the absorbance at lambda max can be used to derive a value of the molar absorptivity. The principal features of ligand field spectra are clearly demonstrated: the great breadth of the spectral bands, that the position of lambda max is dependent on the nature of the ligands and the relatively low values of molar absorptivity.