An efficient ratiometric fluorescent excimer probe for hypochlorite based on a cofacial xanthene-bridged bispyrene

In this paper, by employing a rigid xanthene scaffold as a bridge, we for the first time report a cofacial bispyrene derivative DPH as an efficient ratiometric fluorescent excimer probe for hypochlorite (OCl-). The probe is comprised of a rigid xanthene scaffold and two parallel pyrenes, which are linked by an OCl--sensitive dicarboxylic acid hydrazide group. The introduction of OCl-, however, will induce oxidation of the dicarboxylic acid hydrazide moiety into a diimide group, and the subsequent hydrolysis of the diimide, to give 1-pyrenecarboxylic acid which exhibits a monomer emission at about 380 nm, with its intensity increasing with the addition of increased concentration of OCl-. Meanwhile, the excimer emission intensity gradually decreases. Such a ratiometric fluorescent response of the probe affords a high sensitivity to OCl-, with a linear response concentration range of 1 to 300 mu M, and a detection limit of 0.35 mu M for OCl-. It also shows a high selectivity for OCl- with no interference observed from other common anions and small molecules. Moreover, it can also act as a colorimetric probe for OCl- due to the cyan-to-blue fluorescence color change. It has been preliminarily used for practical detection of OCl- in river water samples with satisfying results.