Extent of intramolecular π stacks in aqueous solution in mixed-ligand copper(II) complexes formed by heteroaromatic amines and the anticancer and antivirally active 9-[2-(phosphonomethoxy)ethyl]guanine (PMEG). A comparison with related acyclic nucleotide analogues

The guanine residue of 9-[2-(phosphonomethoxy)ethyl]guanine leads to intense intramolecular stacks in the ternary complex formed with Cu(1,10-phenanthroline)2+ (aqueous solution). Stacking is more pronounced than with the adenine derivative. The formation degrees of the three isomers, PO32−-coordination only, five-membered chelate with the ether-O, and the intramolecular guanine/phenanthroline stack, are determined.