M. K. Muraleedharan Nair

Rare Earth Iodide Complexes of 4-(2′,4′-Dihydroxyphenylazo) Antipyrine

Abstract Ten new complexes of rare earth iodides with 4-(2′, 4′-dihydroxyphenylazo)antipyrine (H-RAP) of the general formula [Ln(H-RAP)2I2]I (where Ln = Y, La, Pr, Nd, Sm, Eu, Gd, Dy, Ho & Er) have been synthesised and characterized by elemental analysis, electrical conductance in non-aqueous solvents, infrared and electronic spectra, magnetic susceptibilities and thermogravimetric studies. In these complexes H-RAP acts as a neutral bidentate ligand coordinating through carbonyl oxygen and one of the azo nitrogens. Two of the iodines are coordinated and the third one remains as ionic. The magnetic moments of the complexes agree well with the van Vleck values. Thermogravimetric studies in nitrogen indicate that these complexes are stable upto 440 K and undergo complete decomposition in the range 440–1110 K resulting in the formation of the corresponding metal iodides.

Kinetics and mechanism of the thermal decomposition of lanthanum complexes of 4-N-(4'-antipyrylmethylidene) aminoantipyrine

Abstract The kinetics and mechanism of the thermal decomposition of perchlorate, nitrate, chloride, bromide, and iodide complexes of lanthanum with the Schiff base 4- N -(4′-antipyrylmethylidene) aminoantipyrine (abbreviated as AA) have been studied by TG and DTG techniques. The kinetic parameters for the major decomposition stages (stages I and II) were calculated using the Coats-Redfern equation. The rate-controlling process obeys Mampels model with random nucleation, with one nucleus on each particle. It is observed that there is no regular variation in the values of the kinetic parameters of decomposition of the complexes as with other common physical constants, namely boiling point, melting point, etc.

Thermal decomposition kinetics and mechanism of lanthanide perchlorate complexes of 4-N-(4′-antipyrylmethylidene)aminoantipyrine

Abstract The thermal decomposition behaviour of lanthanide perchlorate complexes of the Schiff base, 4- N -(4′-antipyrylmethylidene)aminoantipyrine (AA), have been studied using TG and DTG analyses. The phenomenological and kinetic aspects of the TG curves are investigated for the evaluation of kinetic parameters such as activation energy, pre-exponential factor and entropy of activation using the Coats-Redfern equation. The rate controlling process obeys the ‘Mampel model’, representing random nucleation with one nucleus on each particle. There is no regular variation in the values of kinetic parameters for the decomposition of these complexes. The kinetic parameters indicate that the ligand is loosely bound to the metal ion and the activated complex is more ordered than the reactants.

Complexes of yttrium and lanthanide nitrates with 4-N-(4′-antipyrylmethylidene)aminoantipyrine

Abstract Yttrium and lanthanide nitrate complexes with the Schiff base 4-N-(4′-antipyrylmethylidene)aminoantipyrine (AA) of the composition of [Ln(AA)2(NO3)2]NO3 (where Ln = Y, La, Pr, Nd, Sm, Eu, Gd, Dy, Ho and Er) have been synthesized and characterized by elemental analyses, electrical conductance in non-aqueous solvents, magnetic susceptibility measurements, IR, electronic and proton NMR spectra and thermogravimetric analyses. The Schiff base AA acts as a tridentate ligand in all these complexes, coordinating through the oxygens of both carbonyl groups and the azomethine nitrogen. Only two of the nitrate ions are coordinated monodentately to the central metal ion, while the third remains uncoordinated.

Complexes of Rare Earth Perchlorates with 4-N-(4′-Antipyrylmethylidene)aminoantipyrine

Abstract Rare earth perchlorate complexes with the Schiff base 4-N-(4′-antipyrylmethylidene)aminoantipyrine (AA) of the types [Ln(AA)2ClO4](ClO4)2 (where Ln = La, Pr, Nd, Sm and Eu) and [Ln(AA)3](ClO4)3 (where Ln = Gd, Dy, Ho, Er and Y) have been synthesised and characterised. In these complexes AA acts as a terdentate ligand. One of the perchlorate groups is coordinated monodentately only in the complexes of the light rare earths, whereas in the heavy rare earths perchlorate groups remain uncoordinated. The magnetic moments of these complexes agree well with the van Vleck values, suggesting non-participation of f-electrons in bonding.

Synthesis and Characterisation of Iodide Complexes of Yttrium and Lanthanides With 1, 2-(Diimino-4′-Antipyrinyl) Ethane

Abstract Ten novel complexes of the iodides of yttrium and lanthanides with the Schiff base 1,2-(diimino-4′-antipyrinyl)ethane (GA) having the general formula [Ln(GA)2I]I2, 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, infrared, proton NMR (M = Y and La) and electronic spectra (in the solid and liquid state), magnetic moments and thermogravimetric analysis. The Schiff base GA acts as a neutral tetradentate ligand, coordinating through both carbonyl oxygens and both azomethine nitrogens. One of the iodides is coordinated to the metal ion. A coordination number of nine may be assigned to the metal ion in these complexes.

Rare Earth Perchlorate Complexes of 1,2-(Diimino-4′-Antipyrinyl) Ethane

Abstract A new series of complexes of rare earth perchlorates with the Schiff base 1, 2-(diimino-4′-antipyrinyl)ethane (GA) having the general formula [Ln(GA) 2 (C1O4)] (C1O4) 2, where Ln = Y, La, Pr, Nd, Sin, Eu, Gd, Dy, Ho and Er, have been prepared and characterised by elemental analyses, electrical conductance in non-aqueous solvents, infrared, proton NMR (M = Y, La) and electronic spectra, magnetic moments and thermogravimetric analyses. The Schiff base GA acts as a tetradentate neutral ligand, coordinating through both carbonyl oxygens and both azomethine nitrogens. One of the perchlorate groups in these complexes is coordinated in monodentate fashion to the metal ion. A coordination number of nine is assigned to the metal in these complexes.

Complexes of Yttrium and Lanthanide Bromides with 4-N-(2′-Hydroxybenzylidene) Aminoantipyrine

Abstract Ten new complexes of bromides of yttrium and lanthanides with 4-N-(2′-hydroxybenzylidene)amino-antipyrine (HBAAP) having the formula [Ln(HBAAP)2Br2]Br where Ln = Y. La, Pr, Nd, Sm, Eu, Gd, Dy, Ho and Er have been prepared and characterized. Molar conductance studies indicate 1:1 electrolytic behaviour for these complexes. Their infrared spectra show that HBAAP acts as a neutral tridentate ligand coordinating through the carbonyl oxygen, azomethine nitrogen and phenolic oxygen. Electronic spectra show the weak covalent character in the metal-ligand bond. Thermogravimetric studies indicate that these complexes are stable up to about 170 °C and undergo decomposition in two stages forming the respective metal bromides as the final products.

Synthesis and physicochemical studies of yttrium and lanthanide nitrate complexes of 1,2-(diimino-4′-antipyrinyl)ethane

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.

Synthesis and physicochemical studies of the chloride and bromide complexes of yttrium and lanthanides with 4-N-(4′-antipyryl-methylidene)aminoantipyrine

Twenty new complexes of chlorides and bromides of yttrium and lanthanides with the Schiff base 4-N-(4′-antipyrylmethylidene)aminoantipyrine (AA) have been prepared and characterised. They have the general formula, [Ln(AA)2Cl3] and [Ln(AA)2Br2]Br where Ln = Y, La, Pr, Nd, Sm, Eu, Gd, Dy, Ho and Er. Molar conductance studies indicate slight dissociation for the chloride complexes and 1:1 electrolytic behaviour for the bromide complexes. The magnetic moments of all the complexes agree well with Van Vleck values. The infrared spectra reveal that AA functions as a terdentate ligand in all these complexes coordinating through the oxygens of both the carbonyl groups and the azomethine nitrogen. Electronic spectra of Nd, Ho and Er for the chloride complexes and that of Pr, Nd, Ho and Er for the bromide complexes show weak covalency in the metal-ligand bond.