A dinuclear ruthenium(II) complex as a one- and two-photon luminescent probe for biological Cu(2+) detection

A new dinuclear Ru(II) polypyridyl complex, [(bpy)2 Ru(H2 bpip)Ru(bpy)2 ](4+) (RuH2 bpip, bpy=2,2-bipyridine, H2 bpip=2,6-pyridyl(imidazo[4,5-f][1,10]phenanthroline), was developed to act as a one- and two-photon luminescent probe for biological Cu(2+) detection. This Ru(II) complex shows a significant two-photon absorption cross section (400 GM) and displays a remarkable one- and two-photon luminescence switch in the presence of Cu(2+) ions. Importantly, RuH2 bpip can selectively recognise Cu(2+) in aqueous media in the presence of other abundant cellular cations (such as Na(+) , K(+) , Mg(2+) , and Ca(2+) ), trace metal ions in organisms (such as Zn(2+) , Ag(+) , Fe(3+) , Fe(2+) , Ni(2+) , Mn(2+) , and Co(2+) ), prevalent toxic metal ions in the environment (such as Cd(2+) , Hg(2+) , and Cr(3+) ), and amino acids, with high sensitivity (detection limit≤3.33×10(-8)  M) and a rapid response time (≤15 s). The biological applications of RuH2 bpip were also evaluated and it was found to exhibit low cytotoxicity, good water solubility, and membrane permeability; RuH2 bpip was, therefore, employed as a sensing probe for the detection of Cu(2+) in living cells and zebrafish.