TERNARY COMPLEXES OF CO(II) WITH ADENOSINE 5'-MONOPHOSPHATES, 5'-DIPHOSPHATES, AND 5'-TRIPHOSPHATES AS PRIMARY LIGANDS AND SOME BIOLOGICALLY IMPORTANT ZWITTERIONIC BUFFERS AS SECONDARY LIGANDS

Potentiometric measurements have been made at 25.0 +/- 0.1 degrees C a nd ionic strength I = 0.1 mol dm(-3) KNO3 for the interaction of adeno sine 5'-mono-, 5'-di-, and 5'-triphosphates (AMP, ADP, and ATP) and Co (II) with biologically important secondary Ligand zwitterionic buffers N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid (BES), -[tris(hydr oxymethyl)methyl]-2-aminoethanesulfonic acid (TES), N,N-bis(2-hydroxye thyl)glycine (Bicine), and [tris(hydroxymethyl)methyl]-3-aminopropanes ulfonic acid (TAPS) in a 1:1:1: ratio and the formation of various 1:1 :1 mixed ligand complex species inferred from the potentiometric pH ti tration curves. Initial estimates of the formation constants of the re sulting species and the acid dissociation constants of the resulting s pecies and the acid dissociation constants of AMP, ADP, ATP, and secon dary ligands have been refined with the SUPERQUAD computer program. In some Co(II) ternary systems the interligand interactions have been fo und to be most effective in deciding the stability of the ternary comp lexes formed in solution. Stabilities of mixed ligand complexes increa se in the order AMP < ADP < ATP. The trend in stability constants of t he mixed-ligand complexes of the zwitterionic buffer ligands is in the order TAPS > Bicine > TES > BES.