Chromogenic mercury ions recognition of a new ruthenium(II) complex with cyclometalated 2-(2-thienyl)pyridine in CH3CN-aqueous system

► A cyclometalated ruthenium complex with 2-(2-thienyl)pyridine was synthesized. ► Its maximum MLCT absorption is about 575 nm. ► It can serve as a sensitive naked-eye indicator for Hg2 + with a blue-shift of 120 nm.