• M C Saxena

      Articles written in Journal of Chemical Sciences

    • Influence of electrostatic effect on the stability of mixed-ligand complexes: Uranyl-complexone-phenol/phenolic acid ternary systems

      Anushree Samanta S N Limaye M C Saxena

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      The formation constants (logKMALMA) of the complexes of the type (UO2.A.L] (whereA = IMDA, NTA or EDTA;L = catechol, resorcinol, phloroglucinol, pyrogallol, β-resorcylic acid or protocatechuic acid) have been determined potentiometrically at 25°C and ionic strength,I = 0·2 (mol dm−3, NaClO4) using the Irving-Rossotti approach. The formation constants of the binary complexes (logKKMAKM) have been found to lie in the sequence IMDA < NTA < EDTA, whereas those for the mixed ligand complexes (logKMALMA) follow the reverse sequence, IMDA > NTA > EDTA. due to the electrostatic effect.

    • Tetrad effect in mixed-ligand lanthanide chelates. Part II: Lanthanide. CDTA/DTPA. orcinol/resorcinol/phloroglucinol ternary systems

      Sangeeta Verma M C Saxena

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      The variation profiles of certain properties of the lanthanide [Ln(III)] series show discontinuities at or around Gd(III) (4f7 stage), Nd (IH)-Pm(III) (4f3−4f4 stage) and Ho (III)-Er (III) (4f10−4f11 stage) due to the presence of a tetrad effect. In the present work the occurrence of the tetradic phenomenon has been studied for the formation constants, log KMALMA of the mixed-ligand Ln (III) chelates of the type [Ln(III).A.L], where Ln(III) = La(III), Ce(III), Pr(III), Nd(III), Sm(III), Eu(III), Gd(III), Tb (III) or Dy(III); A = CDTA or DTPA; L = orcinol, resorcinol or phloroglucinol. The presence of the tetrad effect in log KMALMA values has been tested with the help of the straight line approximation method, differential plot method and inclined-W hypothesis. The magnitude of the effect has been found to lie in the sequence f7 > f3 −f4.

    • Complexing tendencies of UO22+ and Th4+ in their mixed ligand complexes with aminopolycarboxylates and resorcinol or its derivatives

      R K Singh M C Saxena

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      Formation contants (log KMALMA) of mixed ligand complexes MAL, where M = UO22+ or Th4+, A = IMDA, NTA, HEDTA, EDTA, CDTA or DTPA, and L = resorcinol (res), 2-methyl resorcinol (2-Me-res), 5-methyl resorcinol (5-Me-res) or 4-chloro resorcinol (4-Cl-res), have been determined pH-metrically by the Irving-Rossotti approach at 25°C and at an ionic strength,I = 0.2(moldm−3KNO3). The observed stability sequences are IMDA > NTA > HEDTA > EDTA > CDTA > DTPA, and 4-Cl-res > 5-Me-res > 2-Me-res > res with respect to primary and secondary ligands, respectively. Th4+ forms more stable mixed complexes than UO22+. The A ΔlogK values are negative due mainly to the charge repulsion involved in the complexation MA + L⇋MAL.

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