C O M M U N I C A T I O N S
Figure 1. Fluorescence emission spectra of purified compounds 1, 1+,
2+, 3+, and 4+ in MeOH (10-5M). The emission intensity of each salt
has been normalized to the emission of 1. Excitation wavelength ) 340
nm.
Figure 3. Fluorescence emission spectra of dimethoxycoumarin-based
sensor in MeOH (10-5M). Excitation wavelength ) 410 nm.
fluorescent acceptor and the amine donor, one methylene unit,
provides the most significant increase in fluorescence intensity upon
reaction with the nerve agent mimic DCP. The response is observed
visually within seconds using a handheld UV lamp. The versatility
of the system with other fluorescent species allows a considerable
range of absorption and emission wavelengths to be accessed.
Acknowledgment. We thank the Skaggs Institute for Chemical
Biology for financial support, and Profs. Tim Swager and Fraser
Hof for helpful discussions. T.J.D. is a Skaggs Predoctoral Fellow.
Supporting Information Available: Additional fluorescent sensors,
detailed descriptions of experimental methods, synthetic procedures,
characterization of new compounds, and additional absorption and
emission spectra. This material is available free of charge via the
Figure 2. (Left) Filter paper with a thin layer of sensor 1 emitting blue
fluorescence. (Right) Filter paper after exposing center portion to 10 ppm
DFP vapor for 5 s. Both are irradiated at 365 nm with a UV lamp.
paper was placed across the top of a vial containing 10 ppm DFP
vapor for a timed exposure period before being removed and
observed again under the 365-nm UV hand lamp. The test was
performed with varying exposure times, and a photograph showing
the results after 5 s of exposure is shown in Figure 2, right circle.
The increased fluorescence intensity is clearly observed in the center
portion that was exposed to the DFP vapor.
The sensor design is modular and not limited to pyrene because
the fluorophore is not involved in the reaction with the phospho-
rylating agent; it only responds to the quaternization event. An
ingenious sensor devised by Swager operates by creating a
fluorophore in response to phosphorylating agents.4 The reactive
module presented here can be deployed with many existing
fluorophores, provided the energetics for electron transfer are
favorable. For example, the amino alcohol module was attached to
6,7-dimethoxycoumarin. The emission spectra before and after
exposure to DCP reveal a 20-fold intensity enhancement using this
longer-wavelength fluorophore (Figure 3). (Note: fluorescence
spectra are obtained on the purified compounds. Φfl(alcohol) )
0.007; Φfl(cyclized salt) ) 0.064.) Additional sensors utilizing
polyaromatic fluorophores perylene and coronene are given in the
Supporting Information.
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In summary, a series of small-molecule fluorescent sensors for
the detection of OP nerve agents were constructed. The pyrene-
based compound containing the shortest spacer between the
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