Mechano-responsive room temperature luminescence variations of boron conjugated pyrene in air

Abstract

Stimuli responsive tunable luminescence is a promising field of research. Even though mechanofluorescence is widely studied, mechanophosphorescence remains unexplored. Here we report the mechano-driven fluorescence and phosphorescence variations of a pyrene tetraboronic ester derivative. The fluorochromic and room temperature phosphorescence features are supported by theoretical studies and single crystal analysis. The mechanically ground fluorescence active but phosphorescence inactive pyrene tetraboronic ester exhibits room temperature phosphorescence in air with mechanical force. The efficient intermolecular electronic coupling in the dimer formed upon scratching enables a good communication between singlet and triplet states, hence resulting in room temperature mechanophosphorescence.

Boron‐Conjugated Pyrenes as Fluorescence‐Based Molecular Probes and Security Markers

“…Solutions of 1 (1 mM in dichloromethane) or 2 (1 mM in EtOAc) are used to prepare a uniform luminescent thin film on regular A4 paper and Whatman paper by dip‐coating. Figure a shows the change in emission color and intensity of the thin film of 1 upon applying mechanical force . Similarly, the thin film of 2 exhibits an increment in emission upon contact with water (Figure b).…”

“…The boron conjugated pyrene derivatives 1 and 2 (Figure a) were synthesized and characterized by following the reported procedure (Scheme S1) . Molecule 1 exhibited mechano‐driven fluorescence and phosphorescence at room temperature .…”

“…Moreover, we applied the mechanoresponsive fluorescence enhancement/variation and self-assembly assisted fluorescence quenching features of these derivatives for fluorescence-based security marker applications.The boron conjugated pyrene derivatives 1 and 2 (Figure 1a) were synthesized and characterized by following the reported procedure (Scheme S1). [13] Molecule 1 exhibited mechano-driven fluorescence and phosphorescence at room temperature. [13] Interestingly, the mechanically ground amorphous sample of 1, which is fluorescence active but phosphorescence inactive displayed room temperature phosphorescence in air upon mechanical grinding.…”

“…[13] Molecule 1 exhibited mechano-driven fluorescence and phosphorescence at room temperature. [13] Interestingly, the mechanically ground amorphous sample of 1, which is fluorescence active but phosphorescence inactive displayed room temperature phosphorescence in air upon mechanical grinding. In this study, we explore the stimuli-responsive fluorescence features of 1 and 2 for selective sensing of F̄anion and glucose, respectively, and thereby developed invisible fluorescent markers for security labeling.…”

Fluorine‐Substituted Tetraphenylethene Isomers with Different Triboluminescence Properties

“…Most of them exhibit the strong piezoelectric effect for their large dipole moments . And the compounds with stronger intermolecular interaction packing may be more likely to exhibit the TL effect owing to the strong intermolecular interactions, which can prevent the molecular slippage and reduce the possible energy loss via non‐radiative relaxation channels under the mechanical stimulation . Fluorine, the most electronegative atom, possesses the highest electron affinity .…”