Study of ternary complexes involving a tridentate and a monodentate ligand with side groups

Abstract

Stability constants of mixed ligand complexes(MAL) [whereM= Cu(II) Ni(II) A= indole acetic acid (IAA) (A)<i>, </i> indole propionic acid IPA (A)<i>, </i> indole butyric acid IBA(A)<i>, </i> L=2-(<i>o</i>-hydroxybenzylamino) acetic acid (HBAA) (¹)= 2-(<i>o</i>-hydroxybenzylamino) propionic acid (HBAP) (L²)= 2-(<i>o</i>-hydroxybenzylamino)-3-(phenyl) propionic acid (HBAPP) L³<i>, </i> 2-(<i>o</i>-hydroxybenzylarnino)-3-(<i>p</i>-hydroxyphenyl) propionic acid (HBAHPP) L⁴,2-[<i>o</i>-hydroxybenzylamino 3-(3-indolyl) propionic acid] [HBAIP]L⁵<i>, </i> have been determined by potentiometric <i>p</i>H titrations in 50% v/v dioxan water medium. The ternary complexes are significantly stable due to intramolecular interligand interactions between indole residue of A and non-coordinating side groups of L. The relative stabilities of Cu(II) and Ni(II) complexes have been explained on the basis of new concept of interaction between metal orbital and non-coordinating group of the two ligands.