Spectrum–structure correlation for visible absorption spectra of copper(II) complexes in aqueous solution

In this study an analysis of visible spectrophotometric data was carried out using more than 100 copper(II) complexes formed by ligands with different coordination environments, and whose aim is the λmax value estimation for equatorially-coordinated copper(II) complexes in solution. Calculations were performed with a least-squares procedure and a bootstrap-based method for accuracy assessment. The results obtained are in good agreement to previous reports describing the coordination of amino, peptide (negatively-charged), pyridine-imidazole nitrogen and carboxylate oxygen, while it was possible to calculate an individual contribution for hydroxide, alcoholate and water oxygen donors. The spectrum–structure correlation for copper(II) complexes in solution is widely discussed in this paper, and an estimation of the uncertainty in relation to the prediction of λmax of copper(II) complexes has also been made.