Abstract
The crystal structure of the cis isomer of cis-bis(l-DOPA-[PHI].sup.2N,O)copper(II) monohydrate (l-DOPA is 3,4-dihydroxy-l-phenylalanine) (CuLD), [Cu(C.sub.9H.sub.10NO.sub.4).sub.2]·H.sub.2O, is a singular example of a structurally characterized, homoleptic, crystalline metal l-DOPA complex. CuLD crystallizes in the space group P2.sub.1, with Z' = 2. The two independent molecules are square planar, and are interconnected by a linear hydrogen-bonded chain containing 12 independent hydrogen bonds. The copper ions in both molecules have weak apical intermolecular Cu...O interactions [2.739 (2) and 2.973 (2) Å] with catechol -OH groups. A survey of the Cambridge Structural Database suggested that cis and trans isomers of Cu(NH.sub.2-C-CO.sub.2).sub.2 amino acid complexes are equally likely to occur. 12 strong O-H...O and N-H...O hydrogen bonds stabilize an unusual linear arrangement of the Cu complexes. The Cu...Cu' distances along the chain are nearly equal [5.0739 (3) and 5.1107 (3) Å] and the Cu...Cu'...Cu angles are nearly linear [176.75 (1)°]. The MATCH procedure available in the Oxford University Crystals for Windows package was used to carry out a detailed analysis of the relationship between the two independent molecules. MATCH has some particular advantages in studying the details of pseudosymmetry, which include: (i) no atomic-order requirements; (ii) the pseudosymmetry matrix is readily available, which allows quick insight into the symmetry elements involved and their location; and (iii) the differences between molecular centroids, as well as between all atomic positions and torsion angles, are listed. A tutorial presentation is designed to attract new users to the technique. In the present case, a search for a pseudosymmetric relationship between the two independent molecules showed that they are related by a pseudo-4.sub.2 axis along the crystallographic c direction. A detailed analysis shows that the pseudo-4.sub.2 symmetry is disrupted by torsions about the CH.sub.2-C(ipso) bonds, and that there is no supergroup that can be used to describe the crystal structure. Supporting information: Additional Supporting Information may be found in the online version of this article Supporting information for this article can be found here Byline: Paul O'Brien, Elizabeth A. Poyner, Thamer S. Alraddadi, Michael B. Hursthouse, Bruce M. Foxman