A highly sensitive and selective colorimetric probe based on a cycloruthenated complex: a Hg2+-promoted switch of thiophene coordination
A cyclometalated ruthenium complex [Ru(pthb)(bpy)2]+ (1, bpy = 2,2’-bipyridine, Hpthb = 3,3-dimethyl-2-(5-pyridylthiophen-2-yl)vinyl- benzo[e]indolium-1-propylsulfonate) could be converted from C-coordination to the non-metallated species with a N,S-bonded Hpthb upon treatment of mercury(II) ion in water. Strikingly, the switch of coordination mode resultes in a great absorption change along with the solution color of 1 varying from dark-red to light yellow. Therefore, 1 can be used as a colorimetric probe to detect mercury(II) ions by naked-eyes. Although the emission was not observed for 1 in water, it still demonstrates an appreciable detection limit of as low as 21 nM by using UV−Vis absorption spectra, which is comparable with those of some probes determined by ratiometric fluorescence spectra.