Tetraphenyethylene-Fused Coumarin Compound Showing Highly Switchable Solid-State Luminescence

Abstract

This paper explores high-contrast mechanoresponsive luminescence (MRL) turn-on materials by combining the features of the coumarin and typical aggregationinduced emission enhancement (AIEE) tetraphenyethylene groups. Therefore, fluorogen C3Ph is obtained by fusing triphenylvinyl and coumarin units, which exhibits typical AIEE characteristics with high solid-state photoluminance (PL) efficiency in the amorphous state. The formation of a unique two-dimensional hydrogen-bonded organic framework (HOF) is responsible for the crystalline-state PL quenching but guarantees the luminescence turn-on to the external stimuli. Furthermore, the reversible solid-state fluorescence on−off cycle for C3Ph can be achieved by alternate grinding and melting−solidifying. This work also offers a way to construct high-contrast MRL turn-on materials by using the HOFinvolved molecules.

Photoacid-Spiropyran Exhibits Different Mechanofluorochromism before and after Modification of Tetraphenylethene under Grinding and Hydrostatic Pressure

“…Compression of the crystal first reduces the intermolecular distances and enhances the intermolecular interactions, which result in the increment of the emission intensities by rigidifying the molecular conformations, and then intermolecular π–π interactions began to form and gradually intensified, which results in the reduction of emission intensity. There are a lot of literature studies investigating the effects of molecular interactions on fluorescence both in ambient pressure and hydrostatic pressure, and the results here are inconsistent with the literature report. ,,,− Meanwhile, the calculation also indicates that molecular conformation of PASP becomes more and more twisted in the compression processes as the dihedral angle between the indole and phenol ring became larger gradually, which also contributes to the reducing of the emission. Unfortunately, calculation of PASPTPE using this method failed because of the large number of atoms.…”

“…For example, by fusing tetraphenylethene (TPE) with coumarin, Huang and co-workers reported a highly switchable solid-state luminescence "turn-on" type of the mechanofluorochromic material. 26 Very recently, Tang and co-workers not only realized the luminescence turn-on but also observed the molecular motion at room temperature in the solid state by manipulating the reversible formation of π−π interactions through scratching. 27 In these systems, π−π interactions formed first; then, they were destroyed, and the fluorescence was turned "on".…”

“…By regulating the formation or perturbation of π–π interactions, the emission change with high on/off contrast has been realized. For example, by fusing tetraphenylethene (TPE) with coumarin, Huang and co-workers reported a highly switchable solid-state luminescence “turn-on” type of the mechanofluorochromic material . Very recently, Tang and co-workers not only realized the luminescence turn-on but also observed the molecular motion at room temperature in the solid state by manipulating the reversible formation of π–π interactions through scratching .…”

Mechanochromic luminogens with hypsochromically shifted emission switching property: recent advances and perspectives

“…Peng et al synthesized a tetraphenylethylene derivative, 32 (Chart 3), and demonstrated its mechanochromic properties. 116 The crystalline sample of 32 exhibited emission maxima at 545 nm with weak fluorescence. When the crystals of 32 were ground into a powder with the help of quartz glass, it hypsochromically shifted its emission to 529 nm and showed a drastic increase in emission intensity (Fig.…”

A New Strategy of Design and Development of Aggregation-Induced Emission Materials Based on a Deep Insight into Mechanism

“…The aggregation-induced emission (AIE) phenomenon first observed from the aggregation of 1-methyl-1,2,3,4,5-pentaphenylsilole was reported by Tang’s group in 2001 . It plays a critical role in organic light-emitting materials − and becomes a hotspot due to its perfect solution to aggregation-caused quenching (ACQ) of chromophoric molecules in the solid state. − …”