1,10-Phenanthroline-5,6-dione and l-tyrosine methyl ester react to form phenanthroline-oxazine (PDT) from which [Cu(PDT)2](ClO 4)2 and [Ag(PDT)2]ClO4·2MeOH are obtained. Binding to calf-thymus DNA by Ag(i) and Cu(ii) PDT complexes exceed bis-1,10-phenanthroline analogues and the minor groove binding drugs, pentamidine and netropsin. Furthermore, unlike the artificial metallonuclease, [Cu(phen)2]2+, the [Cu(PDT)2]2+ complex does not cleave DNA in the presence of added reductant indicating unique interaction with DNA. © The Royal Society of Chemistry.