Eighteen new complexes of lanthanide perchlorates and nitrates with 3-methyl 1-phenyl pyrazol-5-one (MPP) have been synthesized and characterized. The complexes have the general compositions [Ln(MPP)₆] (ClO₄)₂ and [Ln(MPP)₂ (NO₃)₃] where Ln=La, Pr, Nd, Sm, Gd, Tb, Dy, Ho and Y. Conductance studies in nitrobenzene and acetonitrile indicate 1∶3 electrolytic behaviour of perchlorate complexes and non-electrolytic behaviour of nitrate complexes. All the complexes show normal magnetic behaviour. The IR spectra show the monodenticity of the organic ligand and the presence of ionic perchlorate and coordinated nitrate. The electronic spectra indicate 6-coordination for perchlorate complexes and 9-coordination for nitrate complexes. Thermal studies (TG, DTG and DTA) indicate that the perchlorate complexes are thermally less stable than the nitrate complexes.

Rare earth perchlorate complexes of 4–(2′−hydroxynaphthylazo) antipyrine (H-NAP) of the composition [Nn(NAP)₂]CLO₄ (where Ln=La, Pr, Nd, Sm, Gd, Dy and Y) have been prepared and characterised. In these complexes NAP⁻ acts as a tridentate ligand and CLO₄⁻ is uncoordinated. These complexes were screened for their anti-staphylococcal activity by turbidimetric assay method and were found to be more antibacterial than the ligand.

Yttrium and lanthanide nitrate complexes of the Schiff base, 1,2-(diimino-4′-antipyrinyl)ethane (GA), of the type [Ln(GA)₂(NO₃)₃] (where Ln=Y, La, Pr, Nd, Sm, Eu, Gd, Dy, Ho or Er) have been synthesised and characterised by elemental analyses, electrical conductance, magnetic susceptibility, infrared, proton NMR and electronic spectra, and thermogravimetric studies. Infrared and proton NMR spectra of these complexes show that GA acts as a neutral tetradentate ligand and that all the three nitrate groups are coordinated monodentately. The electronic spectra of the Pr, Nd, Ho and Er complexes suggest reasonable covalency in the metal-ligand bond. The magnetic moments of these complexes are in agreement with the van Vleck values. All these complexes are thermally stable up to about 200°C. A coordination number of eleven may be assigned to the metal ions in these complexes.

Complexes of yttrium and lanthanide nitrates with a Schiff base, N,N¹-bis(4-antipyrylmethylidene)ethylenediamine (BAME) having the general formula [Ln(BAME)₂(NO₃)](NO₃)₂, where Ln=Y, La, Pr, Nd, Sm, Eu, Gd, Dy, Ho and Er have been synthesised and characterised by elemental analyses, molar conductance in non-aqueous solvents, electronic, infrared and proton NMR spectra. BAME acts as a neutral bidentate ligand coordinating through both azomethine nitrogen atoms. One of the nitrate groups is coordinated in a bidentate manner. A coordination number of six may be assigned to the metal ion in these complexes. The covalency parameters evaluated from the solid state electronic spectra suggest weak covalent character of the metal-ligand bond.