Coordination complexes of rare earth metals with hydrazine and isomeric acetamidobenzoates as ligands– spectral, thermal and kinetic studies

Abstract

The isomeric acetamido benzoic acids (abbreviated as acambH) on reaction with hydrazine hydrate and lanthanides, La3+, Ce3+, Pr3+, Nd3+, Sm3+ and Gd3+ form complexes of formulae, [Ln{x-C6H4(CH3CONH)}3(N2H4)] where x = 2 (or) 3 (or) 4, at pH 3–4.5 in (1:1) aqueous ethanolic medium, which are insoluble in water and organic solvents. They are characterized by using elemental analysis, IR, UV, 13C, 1H NMR and mass spectroscopic, XRD, SEM-EDAX, thermal and conductance studies. The difference between IR bands of vC=O asym (acid) and vC=O sym(acid) range, 122–166 cm−1 supports the bidental coordination of carboxylate ions to metal. vN-N values of 955 to 980 cm−1, substantiate bridging bidentate coordination of hydrazine to metal. vC=O of amide group 1632 to1709 cm−1 indicates its non-coordination with metal. The thermal studies reveal that complexes undergo dehydrazination between 52 and 180 °C and exothermic degradation into phthalate intermediate between 172 and 496 °C and further degradation to form microsized metal oxide around 600 °C. The magnetic susceptibility measurements indicated that the presence of metals in the same electronic state and electronic spectral assignments suggested that the coordination number is eight for the complexes. The conductance measurement results in DMSO medium indicated that the complexes are neutral. The 13C – NMR, 1H- NMR and the LC-Mass techniques substantiated the composition of the complexes.

Keywords

• Acetamidobenzoic acid
• SEM-EDAX
• Lanthanides
• TG–DTA
• Magnetic susceptibility