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      https://www.ias.ac.in/article/fulltext/jcsc/100/04/0329-0335

    • Keywords

       

      Tervalent lanthanide complexes; 1-(3-aryl 5-hydroxy 4-isoxazolylazo) 4-sulphonic acids; substituent effect; isoequilibrium temperature

    • Abstract

       

      The stability constants of some tervalent lanthanide chelates of 1-(3-aryl-5-hydroxy 4-isoxazolylazo) 4-sulphonic acid (PHI-4S) and its substituents have been carried out by potentiometric and spectrophotometric methods. The results indicated the formation of 1:1 and 1:2 complexes with an order: Yb(III) > Y(III) > Gd(III) > Dy(III) > Tb(III) > Sm(III) > Nd(III) > Pr(III) > La(III). The stabilities increase with a decrease in the ionic or crystal radii [except a small break at Gd(III)], indicates the absence of extensive covalent bonding due to the non-availability of 4f-orbitals for bond formation. Structure-reactivity relationships of complex formation have been discussed by Hammett’s and Irving-Rossotti theories. Thermodynamic parameters have been discussed in terms of iso-equilibrium relationship.

    • Author Affiliations

       

      Ch Nagarjun Rao1 K C Rajanna1 Y Uma Devi1 V Surender Rao1 P K Saiprakash1

      1. Department of Chemistry, Nizam College, Hyderabad - 500 001, India

    • Dates

       
      Published
      August 1988
      Manuscript received
      9 June 1987
      Manuscript revised
      27 May 1988

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