Luminescence Properties of Compressed Tetraphenylethene: The Role of Intermolecular Interactions

Abstract

Mechanochromic materials with aggregation-induced enhanced emission (AIEE) characteristic have been intensively expanded in the past few years. In general, intermolecular interactions invariably alter photophysical processes, while their role in the luminescence properties of these AIEE-active molecules is difficult to fully recognize because the pressurized samples possess amorphous nature in many cases. We now report the high-pressure studies on a prototype AIEE-active molecule, tetraphenylethene, using diamond anvil cell technique with associated spectroscopic measurements. An unusual pressure-dependent color, intensity, and lifetime change in tetraphenylethene has been detected by steady-state photoluminescence and time-resolved emission decay measurements. The flexible role of the aromatic C-H···π and C-H···C contacts in structural recovery, conformational modification, and emission efficiency modulation upon compression is demonstrated through structure and infrared analysis.

Pressure-Induced Conductivity in a Neutral Nonplanar Spin-Localized Radical

“…Moreover, by increasing the pressure the intermolecular interactions become more important that could lead to an enhancement of the photoluminescence as it has been recently reported. 37,38 In order to analyze the reversibility of the photoluminescence properties at high pressure, we have measured the photoluminescence spectrum of the recovered sample at 6 and 12 GPa ( Figure S26). In both cases the intensity of the band remains the same indicating that conformational changes are not reversible and could be originated from a crystalline transition phase.…”

From Two, to Three, to Multi‐Color Switches: Developing AIEgen‐Based Mechanochromic Materials

“…In the higher pressure region, the emission was weak and the normalized ratio of the background at 456 nm from the diamond was raised. In comparison regarding the mechanochromism induced by pressure, the TPE exhibited a relatively smaller red‐shift of 40 nm in maximum wavelength (from 448 nm to 488 nm) at 10 Gpa . It means the more dramatic red‐shift by nearly 100 nm at 10 GPa (from 453 nm to 553 nm) caused by the mechanochromic behavior of SP‐TPE‐1 with an additional twisted spiropyrans under pressure than that of TPE.…”

Pressure-Dependent Relaxation Dynamics of Excitons in Conjugated Polymer Film

“…In our experiment, the energy gap of PDPP-F film decreases with the increase of pressure ( Figure 6b); thus, the lifetime should increase with pressure according to the energy− time uncertainty principle. The increased lifetime may be caused by the fact that the pressure-induced planarization in conjugated polymer may restrict the rotation of the aromatic ring around the connecting linkages, leading to a reduction of the nonradiative rotational relaxation, 38 which eventually causes the long lifetime. Moreover, it is well-known that the diffusion speed of excitons from polymer chain A to polymer chain B represents the diffusion probability of excitons from one to another.…”