New NIR spectroscopic probe with a large Stokes shift for Hg2+ and Ag+ detection and living cells imaging

A new NIR probe based on coumarin-dicyanooxanone dyad an extraordinarily large Stokes shift of 316 nm was developed for simultaneous fluorescence turn-on and colorimetric detection of Hg2+ and Ag+ in aqueous solution. Its application for in vitro U87MG cell imaging to detect Hg2+ was confirmed. [Display omitted] •A coumarin-dicyanooxanone dyad-based NIR fluorescent probe was synthesized.•• The probe displayed an extraordinarily large Stokes shift of 316 nm.•• It serves as colorimetric and fluorimetric probe for detection of Hg2+ and Ag+.•• The applicable pH for sensing Hg2+ by the probe is in a range of 2–12.•• Application of the probe for in vitro cell imaging to detect Hg2+ was confirmed. A new near-infrared (NIR) probe based on a coumarinyl ligand (CL) was designed and synthesized. The probe CL can be used for simultaneous fluorescent turn-on and colorimetric detection of Hg2+ and Ag+ in ethanol/water medium. Colorless solution of probe CL changed to light yellow or dark yellow after addition of Hg2+ or Ag+ ions. Meanwhile the maximum absorption band shifted from 379 nm to 404 nm and the intensity increased enormously (for Hg2+) or moderately (for Ag+). Probe CL displayed an extraordinarily large Stokes shift of 316 nm and addition of Hg2+ or Ag+ to probe CL induced enhancement in the intensity of fluorescence emission at 695 nm by 15 or 8 fold. The detection limit of CL for Hg2+ and Ag+ ions is 0.83 and 8.8 μM, respectively. The applicable pH for sensing Hg2+ by probe CL is in a broad range of 2–12. Application of probe CL for in vitro U87MG cell imaging to detect Hg2+ ions was confirmed.