Upconverting Nanoparticles Prompt Remote Near-Infrared Photoactivation of Ru(II)-Arene Complexes

The synthesis and full characterisation (including X-ray diffraction studies and DFT calculations) of two new piano-stool Ru-II-arene complexes, namely [((6)-p-cym)Ru(bpy)(m-CCH-Py)][(PF)(6)](2) (1) and [((6)-p-cym)Ru(bpm)(m-CCH-Py)][(PF)(6)](2) (2; p-cym=p-cymene, bpy=2,2-bipyridine, bpm=2,2-bipyrimidine, and m-CCH-Py=3-ethynylpyridine), is described and discussed. The reaction of the m-CCH-Py ligand of 1 and 2 with diethyl-3-azidopropyl phosphonate by Cu-catalysed click chemistry affords [((6)-p-cym)Ru(bpy)(P-Trz-Py)][(PF)(6)](2) (3) and [((6)-p-cym)Ru(bpm)(P-Trz-Py)][(PF)(6)](2) (4; P-Trz-Py=[3-(1-pyridin-3-yl-[1,2,3]triazol-4-yl)-propyl]phosphonic acid diethyl ester). Upon light excitation at =395nm, complexes 1-4 photodissociate the monodentate pyridyl ligand and form the aqua adduct ions [((6)-p-cym)Ru(bpy)(H2O)](2+) and [((6)-p-cym)Ru(bpm)(H2O)](2+). Thulium -doped upconverting nanoparticles (UCNPs) are functionalised with 4, thus exploiting their surface affinity for the phosphonate group in the complex. The so-obtained nanosystem UCNP@4 undergoes near-infrared (NIR) photoactivation at =980nm, thus producing the corresponding reactive aqua species that binds the DNA-model base guanosine 5-monophosphate.