Luminescence-based sensing has proven an effective means of measuring analytes such as oxygen, pH, and metal ions at relatively low cost and with high sensitivity, selectivity, and ease of sensor portability. In our laboratories, we are developing a new class of luminescence-based sensors in which analyte-selectivity is shifted from the luminescent reporter molecule to a smart hydrogel in which an environment-sensitive luminescent reporter is incorporated. Relative humidity sensors comprised of the polarity-sensitive fluorophore Dapoxyl sulfonic acid (DSA) embedded in a hydrogel showed that the swelling and contracting of the hydrogel in response to water vapor indeed produces a measurable change in photoluminescence as a result of the changing environment of DSA. However, extension of this sensing scheme to analytes in aqueous phase necessitates covalent attachment of DSA to the smart hydrogel in order to prevent leaching of DSA from the sensing film. Here we describe the synthesis of analogs of DSA that contain a covalently attached acrylate functional group capable of copolymerization with the hydrogel which should prevent leaching and allow for the reuse of the sensor.<br/>In the synthesis of a DSA analog, 4-cyanobenzoyl chloride and 2-amino-4’-bromoacetophenone hydrochloride undergo a Robinson-Gabriel cyclization to produce a 2,5-diaryl oxazole. A protected piperazine derivative is added to the skeleton using a Buchwald-Hartwig amination and provides the core electronics of DSA. The piperazine derivative was chosen, as it yields an electron rich aryl-amine component of the DSA analog and allows for the addition of the acrylamide group which can be co-polymerized in the hydrogel synthesis. Deprotection and acryloylation affords the target luminophore. When synthesizing the model DSA derivative, methods to reduce cost and methods of synthetic efficiency were considered. Future work is aimed at determining photophysical properties of the DSA derivative(s) compared to Dapoxyl sulfonic acid, and determining the potential for use of the derivatives in luminescence-based sensors.

Synthesis and characterization of dapoxyl sulfonic acid analogues for use in aqueous phase luminescence-based sensing

251st National Meeting (2016)

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