Complexes of lanthanide perchlorates with 4-cyano pyridine-1-oxide, 4-chloro 2-picoline-1-oxide and 4-dimethyl-amino 2-picoline-1-oxide have been isolated for the first time and characterized by analysis, conductance, infrared, NMR and electronic spectra. The complexes of 4-cyano pyridine-1-oxides have the composition Ln(CyPO)₆(ClO₄)₃. 2H₂O (Ln=La, Sm, Dy and Ho); Ln(CyPO)₇ (ClO₄)₃. 2H₂O (Ln=Pr, Nd, Er and Yb); and Ln(CyPO)₅ (ClO₄)₃. 2H₂O (Ln=Gd and Tb). The complexes of 4-chloro 2-picoline-1-oxide analyse for the formulae Ln(CpicO)₆ (ClO₄)₃ (Ln=La, Pr, Nd and Ho); and Ln (CpicO)₅ (ClO₄)₃ (Ln=Er and Yb), and those of 4-dimethylamino 2-picoline-1-oxide for Ln(DMPicO)₆ (ClO₄)₃ (Ln=La and Nd); Ln(DMPicO)₇ (ClO₄)₃ (Ln=Gd, Er and Yb); and Ln(DMPicO)₈ (ClO₄)₃ (Ln=Dy and Ho).

Complexes of lanthanide perchlorates with quinoline-1-oxide and isoquinoline-2-oxide, have been isolated for the first time and characterised by analysis, conductance, andir,nmr and electronic spectral studies. The complexes of quinoline-1-oxide have the composition Ln(QNO)₈(ClO₄)₃ where Ln=La, Pr or Nd and Ln(QNO)₇(ClO₄)₃ where Ln=Gd, Dy, Ho, Er or Yb. The isoquinoline-2-oxide complexes analyse for the formula Ln(IsoQNO)₇(ClO₄)₃ where Ln=La−Yb.

2-acetamidopyridine-1-oxide (AcAmPyO) complexes of six lanthanide perchlorates, with the general composition Ln(AcAmPyO)₅ (ClO₄)₃, have been synthesized and characterized by analysis, molar conductance, infrared, proton NMR and electronic spectral data. Infrared and conductance studies indicate the ionic nature of the anion. The coordination of the ligand through the N-O and C=O moieties is shown by the infrared and proton NMR spectral analysis.