Water-soluble luminescent platinum(<sc>ii</sc>) complexes for guanine quadruplex binding

A family of 16 platinum(ii) complexes was synthesized with the aim of obtaining water-soluble luminescent coordination compounds for guanine quadruplex (G4) binding. The complexes share a common tridentate N<^>N<^>C-donor ligand (based on 2-phenyl-6-(1H-1,2,3-triazol-4-yl)pyridine) bearing different substituents for solubilization, and an additional monodentate ancillary ligand (either phenylacetylide or 3-(trimethylammonium)prop-1-yne-1-ide). Single-crystal X-ray diffraction analyses confirm that the substituents do not interfere with the central planar core of the complexes required for pi stacking interactions with the DNA. The interaction of the complexes with four DNA oligonucleotides that fold into various G4 topologies was evaluated using luminescence and circular dichroism spectroscopy as well as cryo-ESI mass spectrometry. The data indicate a complex correlation between type of substituent and ability of the complex to interact with G4 DNA.