pH-Switchable Off-On-Off Near-Infrared Luminescence Based on a Dinuclear Ruthenium(II) Complex

The pH-switchable room-temperature Pear, infrared (NIR) phosphorescence emission based on ruthenium(II) polypyridyl complexes has been very rarely reported, even though it is very, desirable for applications in sensing, switching, and logic molecular devices and bioimaging: Here we report a novel dinuclear ruthenium, (II) complex in an aerated acetonitrile solution featuring a bright NIR emission centered at 760 nm with an absolute quantum yield of 1.03%, a large Stokes, shift of 254 nm, and a long emission lifetime of 108.3 +/- 0.4 ns. The complex in a Britton-Roberson buffer also exhibited pH-induced off-on-off NIR luminescent switches with a maximum intensity enhancement factor of 41 and one of the switching events occurring neat the physiological pH range.