Pressure‐Induced Emission Enhancement of a Series of Dicyanovinyl‐Substituted Aromatics: Pressure Tuning of the Molecular Population with Different Conformations

Abstract

A series of dicyanovinyl-substituted aromatic compounds (Ar-DCV; Ar=9-anthracenyl, 1-naphthyl, 1-pyrenyl) with dual fluorescence are prepared, and their emission properties--when molecularly dispersed in a polymer medium--are investigated under pressure perturbation. The total emission intensity is enhanced drastically from ambient pressure up to 70 kbar. Emission 30-107 times more intense than that at ambient pressure is observed at higher pressure. In dual emission, the enhancement of the local excited state (LE state) is significantly different from that of the intramolecular charge-transfer state (ICT state). The intensity of the ICT emission increases faster (30-370 times) than that of the LE emission (less than 20 times). In accordance with spectroscopic data, emission dynamics at different pressures, and computational studies on the molecular conformations of these compounds, a kinetic model is proposed to explain the effect of pressure on the emissive properties of the Ar-DCV compounds from the point of view of pressure-dependent populations of the species in the ground state.

Facile ACQ-to-AIE transformation via diphenylphosphine (DPP) modification with versatile properties

“…The molecular motions are further inhibited by applying external pressure, contributing to the emission enhancement similar to what has been reported in the literature. [50][51][52][53][54][55][56][57][58][59][60] The rapid intersystem crossing is the internal mechanism of non-luminescence in the solution state, which is different from the previous report that planarization leads to fluorescence quenching. 41…”

The Photophysics of Three Naphthylmethylene Malononitriles

“…The two studies to previously investigate emission in these molecules described the emission of 1-MN (and several other ArCHC(CN) 2 systems) as reflecting the presence two distinct excited states, a locally excited (LE) state and an ICT state having much greater intramolecular charge transfer character. 20,21 The time-resolved spectra of 1-MN and the other solutes recorded here indicate that excitation into S 1 leads to emission from only a single excited state. Comparisons between absorption and emission transition dipole moments (Figure 8) indicate that the absorbing and emitting states do not differ markedly.…”

Understanding the solid state luminescence and piezochromic properties in polymorphs of an anthracene derivative

“…27–33 Whereas an increase in the emissive response has been attributed to mechanisms such as RIR, RIM, the formation of exciton traps and an increase in radiative emission probabilities. 34–39 The emission spectrum is also affected under the application of pressure. Changes in molecular packing lead to a variation in both the emission spectra and photointensity.…”