SYNTHESIS, CHARACTERIZATION, AND AB-INITIO STRUCTURE DETERMINATION FROM POWDER DIFFRACTION DATA OF A NEW X' FORM OF ANHYDROUS COPPER(II) 8-HYDROXYQUINOLINATE DOPED WITH AMINE - MODELING OF THE POLYMORPHIC TRANSFORMATION TO THE STABLE ANHYDROUS BETA'' FORM

A new X' form of anhydrous copper(II) 8-hydroxyquinolinato complex doped with amine has been prepared and characterized. The structure has been solved from X-ray powder diffraction and refined by the Rietveld method. The unit cell is monoclinic, space group P2(1)/c, with the following parameters: a = 10.930(2) angstrom, b = 4.885(1) angstrom, c = 15.184(3) angstrom, beta = 121.21(1)degrees, V = 693.4(1) angstrom3. The structure is close to that of palladium(II) 8-hydroxyquinolinate, with the copper atom lying in a planar square coordination. The molecules are held by van der Waals bonds only. Thermodynamic and kinetic parameters of the X' --> beta'' transformation are determined and compared with other irreversible transformations to the beta'' form. A two-step mechanism is proposed as a model for this polymorphic transition.