Copper-binding motifs: structural and theoretical aspects

In this paper, we report the results of a study involving the coordination geometries of Cu-I, Cu-II, and Cu-III crystal structures in the Cambridge Structural Database, and on Cu binding sites in proteins taken from the Protein Data Bank. The motifs used to bind two bridged Cu ions are also described. In addition, we report the results of ab initio molecular-orbital calculations performed on a variety of model COCO complexes (Cu-I/Cu-II . XnYm (X,Y = NH3, SH2); n + m = 4; n = 0-4) to provide data on the structural and energetic changes that occur in isolated complexes when the oxidation state of the Cu ion is changed from II to I while the coordination number is conserved. The use of such simple ligands in these calculations eliminates constraints on the geometric changes that may be imposed by more-complicated ligands.