P. K. Radhakrishnan

Cobalt(II) complexes of 1,2-(diimino-4′-antipyrinyl)ethane and 4-N-(4′-antipyrylmethylidene)aminoantipyrine

Cobalt(II) complexes of the Schiff bases 1,2-(diimino-4′-antipyrinyl)ethane (GA) and 4-N-(4′-antipyrylmethylidene)aminoantipyrine (AA) have been prepared and characterised by elemental analysis, electrical conductance in non-aqueous solvents, i.r. and electronic spectra, as well as by magnetic susceptibility measurements. The complexes have the general formulae [Co(GA)X]X (X = ClO−4 or NO3−), [Co(GA)X2] (X = Cl−, Br− or I−), [Co(AA)2]X2 (X = ClO4−, NO3−, Br− or I−) and [Co(AA)Cl2]. GA acts as a neutral tetradentate ligand, coordinating through both carbonyl oxygens and both azomethine nitrogens. In the perchlorate and nitrate complexes of GA one anion is coordinated in a bidentate fashion, whereas in the halide complexes both anions are coordinated to the metal, generating an octahedral geometry around the Co ion. AA acts as a neutral bidentate ligand, coordinating through the carbonyl oxygen derived from the aldehydic moiety and the azomethine nitrogen. Both anions remain ionic in the perchlorate, nitrate, bromide and iodide complexes of AA, whereas both anions are coordinated to the metal ion in the chloride complex, resulting tetrahedral geometry around the Co ion.

Thermal Studies on Lanthanide Nitrate Complexes of 4-n-(2′-furfurylidene)aminoantipyrine

The kinetics and mechanism of thermal decomposition of nitrate complexes of lanthanides with the Schiff base4-N-(2′-furfurylidene) aminoantipyrine (abbreviated as FAA) have been studied by TG and DTG techniques. The kinetic data for the first stage of decomposition were calculated using the Coats-Redfern equation. The rate-controlling process obeys Mampel model representing random nucleation, with one nucleus on each particle. It is observed that there is no gradation in the values of the kinetic parameters of decomposition of the complexes.

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.

Complexes of Nickel(II) with 1,2-DI(imino-47′-antipyrinyl)Ethane and 4-N-(4′-antipyrylmethylidene)aminoantipyrine

Abstract Nickel(II) complexes of the Schiff bases 1,2-di(imino-4′-antipyrinyl)ethane (GA) and 4-N-(4′-antipyrylmethylidene)aminoantipyrine (AA) having the compositions [Ni(GA)]X2 and [Ni(AA)2]X2 (where X - ClO4, NO3, Cl, Br or I) have been prepared and characterized by elemental analyses, electrical conductance in non-aqueous solvents, infrared and electronic spectra as well as magnetic susceptibility measurements. GA acts as a neutral tetradentate ligand coordinating through both carbonyl oxygens and both azomethine nitrogens while AA acts as a neutral bidentate ligand coordinating through one of the carbonyl oxygens and the azomethine nitrogen. In all these complexes both the anions are not coordinated resulting in a square planar geometry around the Ni(II) ion in complexes of GA and a tetrahedral geometry in complexes of AA.

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.

Synthesis and antibacterial activity of rare earth perchlorate complexes of 4–(2′–hydroxynaphthylazo)antipyrine

Rare earth perchlorate complexes of 4–(2′−hydroxynaphthylazo) antipyrine (H-NAP) of the composition [Nn(NAP)2]CLO4 (where Ln=La, Pr, Nd, Sm, Gd, Dy and Y) have been prepared and characterised. In these complexes NAP− acts as a tridentate ligand and CLO4− is uncoordinated. These complexes were screened for their anti-staphylococcal activity by turbidimetric assay method and were found to be more antibacterial than the ligand.

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.

Complexes of Copper(II) with 2,3‐Dimethyl‐4‐formyl(benzhydrazide)‐1‐phenyl‐3‐pyrazolin‐5‐one

Copper(II) complexes of the Schiff base 2,3‐dimethyl‐4‐formyl‐(benzhydrazide)‐1‐phenyl‐3‐pyrazolin‐5‐one (L) of the general formula [Cu(L)2]X2 (X = ClO4 or NO3), [Cu(L)Cl2] and [Cu(L)2Br2] have been synthesized and characterized by elemental analyses, electrical conductance in non‐aqueous solvents, infrared, electronic and EPR spectra, as well as magnetic susceptibility measurements. In these complexes, the ligand acts as a neutral bidentate unit coordinating through the azomethine nitrogen atom and the carbonyl oxygen of the pyrazolone ring. In the perchlorate and nitrate complexes both anions remain ionic, while in the corresponding halide complexes both anions are coordinated to the metal ion. The perchlorate, nitrate and chloride complexes are of square‐planar geometry while the bromide complex is of distorted octahedral geometry.