A Dinuclear Ruthenium(II) Complex as a One- and Two-Photon Luminescent Probe for Biological Cu2+ Detection

A new dinuclear Ru-II polypyridyl complex, [(bpy)(2)Ru(H(2)bpip)Ru(bpy)(2)](4+) (RuH(2)bpip, bpy=2,2-bipyridine, H(2)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 Cu2+ detection. This Ru-II complex shows a significant two-photon absorption cross section (400GM) and displays a remarkable one- and two-photon luminescence switch in the presence of Cu2+ ions. Importantly, RuH(2)bpip can selectively recognise Cu2+ in aqueous media in the presence of other abundant cellular cations (such as Na+, K+, Mg2+, and Ca2+), trace metal ions in organisms (such as Zn2+, Ag+, Fe3+, Fe2+, Ni2+, Mn2+, and Co2+), prevalent toxic metal ions in the environment (such as Cd2+, Hg2+, and Cr3+), and amino acids, with high sensitivity (detection limit3.33x10(-8)M) and a rapid response time (15s). The biological applications of RuH(2)bpip were also evaluated and it was found to exhibit low cytotoxicity, good water solubility, and membrane permeability; RuH(2)bpip was, therefore, employed as a sensing probe for the detection of Cu2+ in living cells and zebrafish.