Synthesis and Characterisation of Scandium (III)-, Yttrium (III)-, and Lanthanum (III) Violurate Complexes

Sc³⁺-, Y³⁺ -and La³⁺ violurate complexes were prepared. The isolated complexes are freely soluble in water, dilute mineral acids, MeOH, Me₂CO, DMF, DMS, partially soluble in AcOH and insoluble in EtOH, CHCl₃ and CCl₄. Molecular compositions of the complexes were formulated on the basis of elemental analysis, molar conductivity and infrared spectra. The IR spectra of violuric acid and its metal complexes reveal that bonding takes place through coordination bond between the central metal ion and the oxygen atom of the oxygen atom of the oximino (C N = O) group and convalenet bond between the central metal ion and oxygen atom of the phenolic (ketonic, C O H) group in the case of 1:2 and 1:3 complexes, and through coordination bond between the central metal ion and C O H and N H groups in the case of 2:3 complexes. All the isomorphous complexes detected by the X-ray powder patterns [the (2:3) Sc³⁺-VA and (2:3) Y³⁺-VA complexes, (1:2) Sc³⁺-VA, (1:2) Y³⁺-VA and (1:2) La³⁺-VA complexes, and the (1:3) Y³⁺-VA and (1:3) La³⁺-VA complexes] have similar X-ray, eletronic and IR spetrograms and chemical formulae. The electronic spectra in DMF and in nujol mulls characterise the octahedral stereochemistry for the investigated complexes.