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.
Volume 134, 2022
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