New trivalent lanthanide complexes of phthalate-containing hydrazinium cation — preparation, and spectral and thermal studies

Abstract

Several new lanthanide complexes of the types, (N 2H 5) 2[Ln(C 6H 4(COO) 2) 2.5], A, where Ln is La-Eu except Pm, and N 2H 5[Ln(C 6H 4(COO) 2) 2(H 2O) 3]·H 2O, B, where Ln is Eu-Dy, have been prepared by crystallisation from concentrated aqueous solutions containing the metal nitrates and dihydrazinium phthalate in 1:6 molar ratio. The aqueous solutions of the compounds are acidic and exhibit high values of molar conductance. The complexes were characterised by analytical, magnetic, spectral, thermal and X-ray studies. The OCO − groups of phthalate bridge in both mono- and bidentate fashion as evidenced by IR data. The N-N stretching frequency in the region 960–965 cm −1 supports the non-coordination of N 2H + 5 ions. Both IR and thermal data confirm the presence of three coordinated and one lattice water molecules in the B complexes. Based on the results obtained, a nine-coordination for the lanthanide ions is proposed. Simultaneous TG-DTA of the complexes shows that they are thermally less stable and give metal oxides as the final product. X-ray powder patterns show isomorphism among the A and B complexes but not between them.