Ranjana Dixit

Mixed ligand complexes of manganese(III) with dithiocarbamate and glycine/acetylacetone ligands: magnetic, spectral and thermal studies

SummaryMixed ligand complexes of MnIII with morpholyl and piperidyldithiocarbamates (A) and glycine/acetylacetone (A′) have been prepared with the general formule MnAA′2, MnA2A′ and Mn(A)3, and have been characterised by elemental analysis, magnetic susceptibility measurements, i.r. electronic and e.s.r. spectral techniques and by thermal analysis. The complexes exhibit magnetic moment in the 4.5–5.3 B.M. range. The ligands are bidentate. E.s.r. studies suggest that all the complexes have six-coordinate actahedral geometry. T.g.a. studies reveal one step decomposition of complexes and formation of manganese dioxide.

Thermodynamic studies of the complexation reaction involving trivalent metal ions and benzil-4-methyl-2-quinolylhydrazone (BMQH)

Abstract The stepwise stability constants of 1:1, 2:1 and 3:1 complexes of benzil-4-methyl-2-quinolylhydrazone (BMQH) with lanthanons(III) have been determined pH-metrically in a 75% (v/v) ethanol-water medium at various temperatures and ionic strengths. Values of n and p L have been found by Bjerrum and Calvins method, as modified by Irving and Rossotti. The stability constants and the values of S min have been calculated. The order of stability constants has been found to be La(III) The thermodynamic parameters Δ G , Δ H and Δ S have also been calculated, and the effect of varying dielectric constant of the medium on stabilities has been investigated, at 30 ± 0.5 °C and μ = 0.1 M NaCl.

Evaluation of thermodynamic functions and stability constants of lanthanon(III) complexes with 1,2-naphthoquinone-2-thiosemicarbazone-4-sulphonic acid (sodium salt) (NQTS.4S) from potentiometric data

Abstract Stability constants and thermodynamic functions of formation of 1:1 and 1:2 binary complexes of lanthanons(III) with 1,2-naphthoquinone-2-thiosemicarbazone-4-sulphonic acid (NQTS.4S) ligand have been determined by a potentiometric technique, at various ionic strengths (μ = 0.02, 0.05, 0.10 and 0.20 M NaClO 4 ) in aqueous medium and at various temperatures (20, 30, 40 and 50±0.5°C). The − n and pL values have been subjected to the weighted least squares method to obtain β n values on an HCL Busy Bee PC/AT computer. The values of S min have also been calculated. The order of stability constants has been found to be La(III) G , Δ H , Δ S ) for these complexation reactions have also been evaluated under suitable conditions.

Evaluation of stepwise complexation constants of biologically active ligand with lanthanon ions

The stabilities of the chelates formed by 2-acetylpyridine thiosemicarbazone with La(lII), Pr(III), Nd(III), Gd(III), Sm(III), Tb(III), Dy(III) and Ho(III) have been determined pH-metrically in 75% (v/v) ethanol at various ionic strengths of NaClO4 and at different temperatures. The thermodynamic stability constants and other thermodynamic functions are also reported. The trends in the stability constants for lanthanon(III) complexes has been found to be La(III) < Pr(III) < Nd(III) < Sm(III) < Gd(III) < Tb(III) < DyIII) < Ho(III).

Determination of thermodynamic parameters and equilibrium constants for complexation reactions involving lanthanon(III) ions with 1,2-naphthoquinone-2-semicarbazone-4-sulphonic acid (sodium salt) (NQS · 4S)

The thermodynamic parameters and equilibrium constants of complexation reactions of 1,2-naphthoquinone-2-semicarbazone-4-sulphonic acid (sodium salt) (NQS · 4S) involving lanthanon ions were evaluated by potentiometric estimation of [H+], in aqueous medium at various ionic strengths (0.02, 0.05, 0.10 and 0.20 M NaClO4) and at different temperatures (20, 30, 40 and 50±0.5°C). The −n and pL values calculated by the method of Bjerrum and Calvin, as modified by Irving and Rossotti, were used for the calculation of the equilibrium constants on an HCL Busy Bee PC/AT computer using the weighted least-squares method. The values of Smin were also evaluated. The order of equilibrium constants was found to be Ho(III) > Dy(III) > Tb(III) > Y(III) > Eu(III) > Sm(III) > Gd(III) > Nd(III) > Pr(III) > Ce(III) > La(III). The thermodynamic parameters ΔG, ΔH and ΔS were also calculated at a fixed temperature (30±0.05°C) and ionic strength (0.10 M NaClO4).

Thermal and magnetic studies of mixed ligand complexes of chromium(III) containing dithiocarbamate and acetylacetone/oxine/glycine moieties

Chromium(III) complexes of the type Cr(A)(A′)2, Cr(A)2(A′) and Cr(A)3 have been prepared (whereA is either piperidyldithiocarbamate or morpholyldithiocarbamate andA′ is glycine or oxine or acetylacetone moiety). The mixed ligand complexes have been charac terized by elemental analyses, magnetic susceptibility measurements and thermal studies. The complexes show magnetic moment in the range of 3.5–4.3 B.M. which corresponds to three unpaired electrons. TG studies have also been carried out, in order to study the mode of decomposition of the complexes and to evaluate various kinetic parameters.ZusammenfassungEs wurden Chrom(III)-komplexe des Typs Cr(A)(A′)2, Cr(A)2(A′) und Cr(A)3 (wobei A entweder Piperidyldithiocarbamat oder Morpholyldithiocarbamat und A′ Glycin, Oxin oder Acetylaceton ist) hergestellt. Die Mischligandenkomplexe wurden mit tels Elementaranalyse, Messungen der magnetischen Suszeptibilität und durch thermische Untersuchungen beschrieben. Die Komplexe weisen ein magnetisches Moment im Bereich 3.5–4.3 B.M. auf, was drei ungepaarten Elektronen entspricht. Es wurden auch TG-Unter suchungen durchgeführt, um die Art und Weise der Zersetzung der Komplexe zu untersuchen und verschiedene kinetische Parameter zu bestimmen.

Potentiometric studies on the complexation equilibria involving diacetylmono(lepidyl) hydrazone and bivalent metal ions in aqueous ethanolic medium

The ligand diacetylmono(lepidyl) hydrazone(DALH) has been synthesized in four steps and characterized by melting point, thin layer chromatography, elemental analysis, NMR and IR. Complex formation between transition metal ions Mn(II), Pb(II), Cd(II), Co(II), Ni(II), Cu(II), U02(II) and DALH has been investigated by potentiometric measurements of hydrogen ions liberated on complexation at 25, 30, 40 and 50±0·5°C in 0·02, 0·05, 0·1 and 0·2 M (NaCl) ionic strength and in 75% ethanol-water medium. From the potentiometric titration curves dissociation constants of the ligand and stability constants of its complexes have been determined. Using these stability constants, thermodynamic parameters such as free energy changes (ΔG), enthalpy changes (ΔH) and entropies (ΔS) of complex formation have calculated and reported. Thermodynamic stability constants (logK10) have also been reported. The ligand field stabilization energy (δH) has been calculated for the first row transition metals which is in good agreement with the theory.

Studies on the complexation behaviour of dehydroacetic acid-4-methyl-2-quinolylhydrazone with bivalent metal ions

The complexation behaviour of bivalent metal complexes of dehydroacetic acid-4-methyl-2-quinolylhydrazone (DAMQH) has been studied potentiometrically in 75% (v/v) aqueous dioxan medium at different ionic strengths with respect to sodium perchlorate and at different temperature in order to determine their stability constants. The method of Bjerrum and Calvin as modified by Irving and Rossotti has been used to determine the {ie497-1} andp L values.Smin values which have the same significance as ‘x2’, have also been calculated. The thermodynamic stability constants and the standard free energy change (ΔG) have also been calculated. ΔG values are negative in all cases. Thus complexation is spontaneous. The order of stability constants of bivalent metal complexes of DAMQH has been determined.

Determination of stability constants and thermodynamic parameters of complexes of diacetylmono(LEPIDYL)hydrazone (DALH) with lanthanons

Abstract The consecutive stability constants of the 1:1 and 2:1 chelate species formed by the interaction of diacetylmono(lepidyl)hydrazone (DALH) with lanthanon ions have been determined potentiometrically at various ionic strengths (0.02, 0.05, 0.1 and 0.2 M NaCl) and temperatures (25, 30, 40 and 50°C±0.5°C) in 75% ethanol/water medium. The method of Bjerrum and Rossotti was used to calculate the values of - n and p L . Stability constants, and the values of S min and the thermodynamic parameters Δ G , Δ H and Δ S are reported.

Complexation behaviour of benzilmono(Iepidyl)hydrazone (BLH) toward bivalent metal ions: A potentiometric study

Potentiometric investigations on metal complexes of various bivalent metal ions, viz. UO2(II), Cu(II), Ni(II), Co(II), Cd(II), Pb(II), Zn(II) and Mn(II) with benzilmonol(lepidy!)hydrazone (BLH) have been carried out at different ionic strengths and at different temperatures in order to determine stability constants of the complexes. Thermodynamic parameters ΔC, ΔH and ΔS have also been evaluated from temperature coefficient data. The effect of varying the dielectric constant of the medium on the stability constants of complexes has also been investigated at 30±0.5°C and μ = 0.1MNaCl. Thermodynamic stability constants and thermodynamic stabilization energies for the first transition metals have also been discussed.