Trivalent lanthanide complexes of the type K[ML₂] whereM=La(III), Pr(III), Nd(III), Sm(III), Eu(III), Gd(III) and Dy(III) and H₂L=N-isonicotinamidosalicyladimine, have been prepared and characterised. The nephelauxetic ratio (β), covalency (δ) and bonding parameter (b²) of K[NdL₂] have been calculated. Infrared spectral studies reveal that N-isonicotinamidosalicylaldimine acts as a dibasic tridentate ligand. A coordination number six has been proposed for the lanthanide metal ions.

Tyrosine hydrazide (TH) has been found to form complexes of the types [M(TH)₃Cl₂]Cl [M=La(III), Pr(III), Nd(III)] and [M′(TH)₂Cl₂]Cl [M′=Sm(III), Eu(III), Gd(III) and Dy(III)]. The complexes have been characterized by elemental analysis, molar conductance, magnetic susceptibility, infrared, electronic and PMR spectral studies. The nephelauxetic ratio (β), covalency (δ) and bonding parameter, (b^1/2) of [Nd(TH)₃Cl₂]Cl have been calculated. Infrared spectral studies reveal that TH acts as a neutral bidentate ligand. Coordination numbers of eight around La(III), Pr(III) and Nd(III) and six around Sm(III), Eu(III), Gd(III) and Dy(III) have been proposed in the complexes.

Some trivalent lanthanide complexes of acetone isonicotinoylhydrazone (AINH), having the empirical formula Ln(AINH)₃Cl₃, where Ln=La(III), Pr(III), Nd(III), Sm(III), Eu(III), Gd(III), Tb(III), Dy(III) and Y(III) were prepared. Elemental analyses, molar conductance, magnetic susceptibility, IR, electronic,¹H,¹³C and¹³⁹La NMR spectra of the complexes have been examined. It has been found that AINH behaves as a neutral bidentate ligand coordinating through the carbonyl oxygen and azomethine nitrogen. Temperature-dependence of the molar absorptivity and the metal coordination number has been established by the electronic spectra of Nd(AINH)₃Cl₃ recorded over the 28–80°C range.

Metal complexes of the empirical formula [M(Hpbzgh)₂], where H₂pbzgh=pyridoxalN-benzoylglycyl hydrazone and M=Mn(II), Co(II), Ni(II), Cu(II), Zn(II), have been synthesized and their structures studied by electronic, IR,¹H and¹³C NMR spectra. IR and NMR spectral data indicate uninegative tridentate coordinated ligand bonding through hydrazidic carbonyl/imidolic oxygen, azomethine nitrogen and phenolate oxygen with its pyridoxal moiety in hemi-acetal as well as normal forms. Magnetic and electronic spectral data suggest distorted octahedral geometry for the Mn(II), Co(II), Ni(II) and Cu(II) complexes.

2,4-Dihydroxybenzaldehyde(N-benzoyl)glycyl hydrazone, H₃ dhbbgh, has been synthesized and characterized. Rare earth metal complexes of the empirical formulae, [Ln(H₃dhbbgh)₂Cl₂]Cl.nH₂O and [Ln(dhbbgh)(H₂O)₂], where Ln=La(III), Pr(III), Nd(III), Sm(III), Eu(III), Gd(III), Tb(III), Dy(III) and Y(III) have been synthesized and characterized by elemental analyses, molar conductances, magnetic susceptibilities, electronic, infrared and NMR spectral studies. Various bonding parameters (β, b^1/2, %δ andη) calculated from the electronic spectra of Pr(III), Nd(III), Sm(III) and Dy(III) complexes suggest a weak covalent bond between the metal and ligand. The theoretical oscillator strengths (P_calcd) and a set of three intensity parameters (T_λ=2,4.6) computed from the Judd-Ofelt equation are found to be in good agreement with experimental values. On the basis of the spectral profiles of the hypersensitive transitions (⁴I_9/2→⁴G_5/2,²G_7/2) in the Nd(III) complexes, coordination numbers ten and six have been proposed for the Ln(III) ions in the adduct and deprotonated complexes respectively.

Complexes of Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II) with 2-acetyl pyridine (N-benzoyl) glycyl hydrazone(2-ApBzGH) have been synthesized and characterized by elemental analyses, molar conductances, magnetic susceptibility, IR, electronic, ESR,¹H,¹³C and¹¹³Cd NMR spectral and X-ray diffraction studies. IR and NMR data suggest the tridentate nature of the ligand coordinating as a neutral species in the addition complexes and as a uninegative species in the deprotonated complexes. The presence of more than one isomer of the ligand has been established by¹H NMR spectra of the ligand and complexes recorded over the 298–396 K range. The X-ray powder diffraction patterns of [Cd(2-ApBzGH)Cl]Cl and [Cu(2-ApBzGH)Cl(H₂O)₂]Cl are indexed for orthorhombic and tetragonal crystal systems respectively.