Electronic absorption spectra for copper(II) polyamine complexes

The preparations and visible and ultraviolet absorption spectra are reported for a series of copper(11) complexes with linear and cyclic aliphatic ligands which each have four nitrogen donor atoms. Data are compared with that for 16 analogous complexes. For linear polyamines of different chain length the ligand field strength, as denoted by vmax (visible), is found to increase with increasing thermodynamic stability of the copper(11) complex in aqueous solution. For linear and cyclic ligands the ligand field strength is a maximum for complexes containing a combination of five- and six-membered chelate rings.