Polymorphism and Phase Transitions in Bis(glycinato)copper(II). A Powder Diffraction Study

Abstract

Powder diffraction methods have been used to establish the structures of four known polymorphs of bis(glycinato)copper(II). The two cis-modifications are orthorhombic, and the two trans-complexes are monoclinic. Refinements of the structures, including the location of the hydrogen/deuterium atoms have been achieved utilizing Rietveld analysis of powder data. The cis-monohydrate complex crystallizes in the space group P2₁2₁2₁ with lattice parameters a 10.8053(3), b 5.2101(1), and c 13.4983(4) Å. Upon dehydration, contraction along the a- and c-axes and elongation of the b-axis is observed. The anhydrous cis-complex also crystallizes in the space group P2₁2₁2₁ with lattice parameters a 10.0673(7), b 5.3152(4), and c 13.212(1) Å. The trans-hydrated complex crystallizes in the space group I2/a with lattice parameters a 14.8218(3), b 5.2321(1), and c 9.6408(2) Å, and β 87.243(1)°. Dehydration of the complex affords the anhydrous modification which crystallizes in the space group P2₁/c with lattice parameters a 7.0831(6), b 5.1459(4), and c 9.4431(9) Å, and β 107.506(4)°. In all four modifications a network of hydrogen bonds stabilizes the complex. This study illustrates the current capabilities of powder diffraction techniques.