Structural and thermal properties of rare earth complexes with 2,2'-biphenyldicarboxylic acid

Rare earth complexes with 2,2'-biphenyldicarboxylic acid (diphenic acid = H(2)dpa) were obtained as hydrated precipitates of the general formula Ln(2)(C14H8O4)(3)a (TM) nH(2)O, where n = 3 for the of Y(III) and Ce(III)-Er(III) and n = 6 for La(III), Tm(III), Yb(III) and Lu(III) complexes. On heating in air atmosphere complexes lose all water molecules in the temperature range 30-210 A degrees C in one step and form anhydrous compounds, which are stable up to 315-370 A degrees C. During further heating they decompose to oxides. The trihydrated compounds are crystalline powders whereas the hexahydrated are amorphous solids. The trihydrated complexes crystallize in the monoclinic (Pr(III) and Ce(III) complexes) and triclinic (Y(III) and Nd(III)-Er(III) complexes) crystal systems.