METAL-ION DISTRIBUTION AND SOLUBILITY OF MN1-XCUX(HCOO)2-CENTER-DOT-2 H2O MIXED-CRYSTALS

The metal ion distribution on the two metal sites of monoclinic Mn1-xCux(HCOO)2.2(H,D)2O mixed crystals are studied by infrared and Raman spectroscopic methods. The spectral regions 3200 - 3400 cm-1 (nu(OH)), 2875 - 2990 cm-1 (nu(CH)), 2330 - 2500 cm-1 (nu(OD)) of matrix isolated HDO molecules), 1350 - 1400 cm-1 (symmetric CO2 stretching modes), 570 - 950 cm-1 (H2O librations), and < 490 cm-1 (M-O lattice modes) are mostly sensitive to the metal ions present. The frequency shifts of these bands with increasing content of copper show that Cu2+ prefers the M(1) site, coordinated by HCOO- only. The strengths of the hydrogen bonds increase on going from manganese to copper formate, due to the increased synergetic effect of Cu2+. Solubility and X-ray data of the mixed crystals are included. Irrespective of the same crystal structure, two series of mixed crystals are formed: eutonic area at 0.65 greater-than-or-equal-to x greater-than-or-equal-to 0.5.