The crystal structure of bis-(L-threonine) copper (II).H₂O, Cu (C₄H₈NO₃)₂.H₂O has been determined by heavy atom and Fourier methods and refined by least-squares using visually estimated three-dimensional x-ray data of 893 reflections. The blue crystals are monoclinic, space groupP2₁ withα=11·02,b=4·90,c=11·16Å andβ=93·5°,Z=2. The finalR is 0·10. Coordination of copper is distorted square pyramidal with ligands intrans configuration. The conformation of one of the aminoacid ligand is identical with L_s-Threonine while the other has a conformation with torsional angleχ^{1, 2}=−74(1)°.

The crystal and molecular structure of (L-proline-L-alanine) Cu·2·5 H₂O has been determined by the heavy atom method with 583 visually estimated reflexions and refined by full matrix least squares toR=0·101. The crystals are monoclinic witha=16·47 (3),b=7·74 (2),c=9·51 (3) Å andβ=109·7 (5)°; space groupC2;Z=4. The copper coordination is nearly square pyramidal with one water in the basal plane and another occupying the apical together with the aminoN, peptideN and the carboxylO of the dipeptide in the coordination. The Cu-peptide-Cu linkage isvia the hydrogen bonding between the water in the basal plane and the carbonyl O atom of the proline residue. One water is on the 2-fold axis.