Multiple equilibrium studies on some zinc (II) mixed ligand complex systems

Abstract

Multiple equilibrium studies involved in some Zn(II) ternary systems viz. Zn(II)-<img src='http://www.niscair.res.in/jinfo/small.gif' border=0>-cysteine (cys)/<img src='http://www.niscair.res.in/jinfo/smaller.gif' border=0>-pencillamine (pen)/<img src='http://www.niscair.res.in/jinfo/small.gif' border=0>-cysteic acid (cya) (A)-<img src='http://www.niscair.res.in/jinfo/smaller.gif' border=0><img src='http://www.niscair.res.in/jinfo/small.gif' border=0>-2,3-diaminopropionic acid (dapa), <img src='http://www.niscair.res.in/jinfo/smaller.gif' border=0><img src='http://www.niscair.res.in/jinfo/small.gif' border=0>-2,4-diaminobutyric acid (daba) and <img src='http://www.niscair.res.in/jinfo/smaller.gif' border=0><img src='http://www.niscair.res.in/jinfo/small.gif' border=0>-ornithine (orn) (B) by the computer analysis of the <i>p</i>H titration data have shown the presence of ZnABH₂, ZnABH or ZnAB type ternary species. The trends in the results demonstrate the possibility of attachment of an extra proton in the ZnABH species to be with ligand (B). In the ZnABH₂ species, one proton resides with ligand (A) and the other with ligand (B). The mode of coordination of cys, pen, dapa, daba and orn ligands in the ZnAB type species is similar to their coordination in the corresponding binary species. However, in the ZnAB and ZnABH species in.the Zn(II)-cya(A)-dapa, daba and orn (B) systems, cya (A) ligand binds the metal in a glycinelike mode though it is monodentate in its ZnA and ZnA₂ binary species.