Pentacenequinone derivatives: Aggregation-induced emission enhancement, mechanism and fluorescent aggregates for superamplified detection of nitroaromatic explosives

Abstract

Pentacenequinone derivatives 5–9 have been synthesized by a Suzuki–Miyaura coupling protocol. These derivatives form fluorescent aggregates in mixed aqueous media due to their aggregation-induced emission enhancement (AIEE) attributes. Interestingly, size dependent emission enhancement is observed in the case of derivatives 5–7 and the effect of increase in the number of pyridine rotors on fluorescence emission of pentacenequinone derivatives 6–7 in solution and in the aggregate state confirms that the AIEE phenomenon is at the cost of aggregation driven growth and restriction of intramolecular rotation (RIR). On the other hand, derivatives 8 and 9 having electron rich phenyl groups are donor–accepter–donor type systems which exhibit an intermolecular charge transfer state (ICT) and form fluorescent aggregates in mixed aqueous media. In addition to this, the AIEE characteristics endow pentacenequinone derivatives 5–9 with sensing functionalities such as detection of nitroaromatic compounds. TLC strips of AIEE-active pentacenequinone derivatives 5–9 provide a more convenient and cost-effective approach for the trace detection of nitroaromatic explosives.