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

Abstract

The pH-switchable room-temperature near-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 near the physiological pH range.

Bioinspired photo-crosslinkable self-assembling peptides with pH-switchable “on–off” luminescence

“…The above mentioned four luminescent "on−off" states are reported on Figure 3c and Figure S2, thus confirming the propensity of the photo-cross-linked SAP to have "off−on−off−on" luminescence switchable from acid to basic pH. Notably, as previously reported on others ruthenium-based complex, this "on−off" emission switching could be associated with the deprotonating-protonating processes among ruthenium complex at different pH values [53]. In brief, the imidazole rings uncoordinated to the Ruthenium, can exhibit three independent ground-state protonation/deprotonation processes under differ pH values with a transition from the state [Ru(bpy) 3 ] 2+ to the state [Ru(bpy) 3 ] 4+ (+2H), or to the state [Ru(bpy) 3 ] 5+ (+1H) and vice versa [54][55][56][57].…”

Stimuli-Responsive Near-Infrared Emissive Os(II)–Terpyridine Complexes with a Sense of Logic

“…79 Ru1(ClO 4 ) 4 , where bpy = 2,2-bipyridine, HL 1 = 2-(2,6-di(pyridin-2-yl)-pyridin-4-yl)-1H-imidazo[4,5-f]-[1,10] phenanthroline, and H 2 L 2 = 2,6-bis(benzimidazol-2-yl)-pyridine. 80…”

Determination and Imaging of Small Biomolecules and Ions Using Ruthenium(II) Complex-Based Chemosensors

“…Dinuclear Ru(II) complex 21 was then synthesized by Meng and co-workers in 2017 (Fig. 11 A) [ 117 ]. Ru(II) complex 21 showed NIR emission at 760 nm with a large Stokes shift of 254 nm and lifetime (τ) 108.3 ± 0.4 ns.…”