Synthesis and Characterization of Ternary Hetero Chelates of La(III), Pr(III), Nd(III) and Sm(III)

Abstract

Ternary hetero chelates of La(III), Pr(III), Nd(III) and Sm(III) with

7-hydroxy-4-phenyl-6-(α-naphthyl)-aminomethyl coumarin (HPAC) as

primary and 2-thiopyrogallol as co-ligand have been synthesised and characterised

on the basis of analytical, magnetic, spectral and thermal studies.

The chelates have the general formula [Ln(HPAC)(TG)X₂], where

Ln = La(III), Pr(III), Nd(III), and Sm(III), HPAC = 7-hydroxy-4-phenyl-6-

(α-naphthyl)-aminomethyl coumarin, TG = 2-thiopyrogallol (mono

deprotonated), X = Cl, NO₃. The lower Λ_m values (4.0-4.8 moles) in

DMSO indicate their non-electrolytic nature. The compounds are nonhygroscopic

and air stable. They are insoluble in common organic solvents

but dissolve in DMSO and DMF considerably. The magnetic moment and

reflectance spectral data of the complexes suggested octahedral configuration.

IR spectra of the ternary chelates showed bidentate behaviour of both

the ligands. In HPAC, nitrogen atom of —NH group and oxygen of —OH

group form bond with the metal ion while TG participates through the

oxygen atom of —OH group and sulphur of deprotonated —SH group.

All the complexes decompose endothermally at ∼430ºC with the

elimination of HPAC. In the temperature range 670-730ºC, thiopyrogallol

molecule is also lost and finally, a metallic oxide residue is obtained.