Triptycene-Derived Photoresponsive Fluorescent Azo-Polymer as Chemosensor for Picric Acid Detection

Abstract

Two new triptycene-based azobenzene-functionalized polymers (<b>TBAFPs</b>) have been synthesized using the well-known Pd-catalyzed Sonogashira cross-coupling polycondensation reaction between 2,6-diethynyltriptycene and (<i>meta</i> or <i>para</i>) dibromo-azobenzenes. Enhancement of the fluorescent emission intensity was observed upon trans → cis isomerization of -N=N- linkage in <b>TBAFPs</b>. The cis-lifetime of <b>TBAFP1</b> is rather long (greater than 2 days). The resulting materials were tested as a potential chemosensor for the detection of picric acid (PA)-a water pollutant as well as chemical constituent of explosives used in warfare. PA was found to interact strongly with <b>TBAFPs</b>, which led to significant quenching of the latter's fluorescence emission intensities. The binding constants are in the order of 10⁵ M^-1. <b>TBAFPs</b> were also able to detect PA in nanomolar concentrations.