Near-infrared emission of dibenzoxanthenium and its application in the design of nitric oxide probes.

Two dibenzoxanthenium derivatives bearing a 3,4-diaminophenyl group, compounds 1a and 1b, have been prepared and evaluated as near-infrared probes for the detection of nitric oxide. Compound 1a gave a 3-fold emission enhancement towards nitric oxide at 681 nm, whereas compound 1b exhibited OFF-ON emission behavior towards nitric oxide, resulting in a 35-fold increase in the fluorescence intensity with an emission maximum of 750 nm being approved through (TD)DFT calculations. Probe 1b showed independent emission in the presence of common cations, amino acids, reactive oxygen and nitrogen species; furthermore, it can be used for the in cellulo imaging of nitric oxide under acidic and neutral conditions.