Synthesis, structure, optical, photoluminescence and magnetic properties of K2[Co(C2O4)2(H2O)2].4H2O

The synthesis, crystal structure, optical, photoluminescence and magnetic behaviour of potassium bis(oxalato) cobaltate(II) tertrahydrate{K-2[Co(C2O4)(2)(H2O)(2)].4H(2)O} are described. The compound was grown at room temperature from mixture of aqueous solutions by slow evaporation method. The X-ray crystallographic data showed that the compound belongs to the monoclinic crystal system with P2(1)/n space group and Z= 4. The UV-visible diffuse absorbance spectra exhibited bands at 253, 285 and 541 nm in the visible and ultraviolet regions. The optical band gap of the compound was estimated as 3.4 eV. At room temperature, an intense photoluminescence was observed from this material around 392 nm when it excited at 254 nm. The variable temperature dc magnetic susceptibility measurements exposed paramagnetic behaviour at high temperatures and antiferromagnetic ordering at low temperatures.