Search

The molecular crystals of acridonyl-tetraphenylethene (AD-TPE) exhibit an intriguing turn-on and color-tuned luminescence in response to mechanical grinding and hydrostatic compression. On the basis of in-depth experimental and computational studies, it is hypothesized that the origin of the piezochromic behavior from the D-phase to the B-phase is the change of the intramolecular geometrical conformation, especially for the torsion angle between the TPE and AD moiety. The different molecular conformation in the two distinctive solid phases causes the substantial switching of the intra­molecular charge transfer (ICT) process, which can be directly correlated with the subsequent fluorescence from locally excited (LE) state and ICT state in both phases. The AD-TPE molecular system presents a very rare example of high-contrast reversible fluorescence tuning driven by a switching of the excited state in the solid state under the mechanical stimuli, and thus provides a novel mechanism of the piezochromic behavior. [ABSTRACT FROM AUTHOR]

Two 9,10-distyrylanthracene (DSA) derivatives CNDSA and t-BUDSA were designed and synthesized, and their photophysical properties and crystal structures were investigated. Compared to DSA, the maximum emission peaks of the two compounds showed red-shift not only in THF solution, but also in crystals, because the introduction of electron-withdrawing substituents to DSA leads to more dispersion of the electrons in the molecules. The two crystals of CNDSA and t-BUDSA show strong fluorescence with the efficiency Φ of 45% and 33%, respectively, which may be resulted from no obvious π-π interactions between molecules inside the crystal due to the large distance between the two adjacent molecules and nearly no overlap between the central anthracene planes. The analysis of crystal structures of the two compounds indicated that the molecules are arranged in the same conformation and orientation in their crystals, i.e. uniaxially oriented packing crystal, because of the supramolecular interaction of CH/π in the two crystals and additional C-H...N interactions in CNDSA. [ABSTRACT FROM AUTHOR]

Turn‐on and color‐tuned piezochromic luminescence of acridonyl‐tetraphenylethene(AD‐TPE) with high‐contrast is obtained by B. Xu, W. Tian, and colleagues in response to external mechanical stimuli. The results on page 4005 indicate that the unique behavior is driven by a switching of the excited state in solid state from localized excited (LE) state to intramolecular charge transfer (ICT) state under mechanical stimuli, which will inspire a new approach to realize the piezochromic luminescent materials and give a new insight into the nature of the piezochromic behavior. [ABSTRACT FROM AUTHOR]