The stability constants of the binary complexes comprising Zn 2+ or Cd 2+ and 2 picoline

2

4 lutidine or 2

4

6 collidine and ternary mixed ligand complexes containing in additional adenosine 5′ triphosphate(ATP) were determined by potentiometric pH titration in aqueous solution. Comparing these data with those of the corresponding complexes containing ammonia instead of pyridine like ligands

it has been found that an intramolecular stacking interaction exists between the pyridine like ligands and the purine moiety of ATP in the ternary complexes

and the interaction is related to the structure of coordination spheres of the central metal ions.