Intramolecular π-π stacking interactions in aqueous solution in mixed-ligand copper(II) complexes formed by heteroaromatic amines and the nucleotide analogue 9-[2-(phosphonomethoxy)ethyl]-2-aminopurine (PME2AP), an isomer of the antivirally active 9-[2-

The stabilities of the ternary Cu(Arm)(PME2AP) complexes, where Arm = 2,2′-bipyridine or 1,10-phenanthroline, were measured and the extent of the intramolecular π-π stacking between the purine residue and the Arm-rings calculated. It is speculated that the lower stacking properties, compared to those of the antivirally active PMEA, and the different hydrogen-bonding properties of the 2-aminopurine residue, are responsible for the very modest antiviral activity of PME2AP.