Pyrene-substituted cyclic triimidazole: An appealing and versatile luminescent scaffold for explosive detection

Two derivatives of cyclic triimidazole and pyrene, namely the blue emitting 3-(pyren-1-yl)triimidazo[1,2-a:1′,2′-c:1″,2″-e] [1,3,5]triazine, TTPyr, and the yellow-orange emitting 11-(pyren-1-yl)triimidazo[1,2-a:1′,2′-c:1″,2″-e][1,3,5]triazine-3,7-dicarbaldehyde, (CHO)2TTPyr, are here exploited for titration experiments with various nitroaromatic energetic hazardous materials and proposed as sensor species for the quantitative detection of explosives. The 565 nm fluorescence of (CHO)2TTPyr represents a valid alternative to the TTPyr 420 nm one for analytes absorbing in the blue region. (CHO)2TTPyr displays varying degrees of fluorescence quenching towards different nitroaromatics, among which picric acid (PA) detection has the highest sensitive response with a Stern-Volmer quenching constant value equal to 1.25 × 104 M−1 and a calculated detection limit of 0.63 ppm. From time resolved photoluminescence experiment, a static mechanism is recognized as responsible for the observed quenching. The hypothesis of a dark complex formation is supported through the isolation and characterization of a TTPyr/PA adduct with 2:1 stoichiometry.