Strain-Promoted Alkyne-Azide Cycloaddition (SPAAC)-Based Bioorthogonal Labeling, Bioimaging, and Photocytotoxicity Studies of Phosphorescent Ruthenium(II) Polypyridine Dibenzocyclooctyne (DIBO) Complexes

Four new ruthenium(II) polypyridine complexes functionalized with a dibenzocyclooctyne (DIBO) or amine moiety, [Ru(N^N)2(L)](PF6)2 (N^N = bpy, phen; L = bpy-DIBO, bpy-NH2) have been synthesized. The electronic absorption, photophysical properties, and lipophilicity of these complexes have been studied. The azide-reactive DIBO complexes have been used as bioorthogonal probes for the cell-surface N-azidoglycan units of Ac4ManNAz-pretreated cells through the SPAAC reaction. The live cell labeling properties of the DIBO complexes have been examined by laser-scanning confocal microscopy, flow cytometry, and ICP-MS.