The effects of the high pressure on two single crystals, pyrene and N,N-diphenyl-4-(pyren-1-yl)aniline (TPA-Py), were studied by in situ fluorescent and Raman spectroscopies. During the compression, the pyrene with one structureless excimer emission band showed a continuous bathochromic-shift. In contrast, with the pressure increasing to 10.36 GPa, TPA-Py previously dominated with the hybridized local and charge transfer (HLCT) excited state gradually exhibited a new band at longer wavelengths, which is assigned to a new excited state species with the intramolecular charge transfer (ICT) state, caused by the pressure-induced changes on its molecular configuration. Accompanied by the spectral changes, a sequential color variation from blue to cyan was observed, giving a change to yellow and then red. The significant broadening of the full-width half-maximum (FWHM) of the TPA-Py is observed due to the enhanced dipole-dipole interaction and the existence of pressure gradient. Both pyrene and TPA-Py showed the delayed recovery of the luminescence in the compression-decompression cycle, which results from the poor reversibility of electronic structure caused by the compression-induced piezochromic effect. Furthermore, the evolutions of the Raman spectra of pyrene and TPA-Py indicated that the pressure-induced reversible transformation is caused by the molecular conformational change. This study is a deeper understanding of the structure-property relation of the HLCT species and will be a helpful reference for the regulation of photoluminescence in these intramolecular electron donor-acceptor crystal materials.

中文翻译：

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和TPA-Py单晶的压力依赖性不同的发光演化。

通过原位荧光和拉曼光谱研究了高压对两种单晶pyr和N，N-二苯基-4-（吡喃-1-基）苯胺（TPA-Py）的影响。在压缩过程中，具有一个无结构准分子发射带的the表现出连续的红移。相反，随着压力增加到10.36 GPa，先前以杂化的局部和电荷转移（HLCT）激发态为主的TPA-Py逐渐在更长的波长处显示出一个新的谱带，该谱带被分配给具有分子内电荷的新的激发态物质。转移（ICT）状态，是由压力诱导的分子结构变化引起的。伴随光谱变化，观察到从蓝色到青色的连续颜色变化，从而给出从黄色到红色的变化。由于增强的偶极-偶极相互作用和压力梯度的存在，可以观察到TPA-Py的半峰全宽（FWHM）显着加宽。and和TPA-Py均在压缩-减压循环中显示出延迟的发光恢复，这是由于压缩引起的压致变色效应导致电子结构的可逆性差所致。此外，of和TPA-Py的拉曼光谱的演变表明，压力诱导的可逆转变是由分子构象变化引起的。这项研究是对HLCT物种的结构-性质关系的更深入了解，并将为调节这些分子内电子供体-受体晶体材料中的光致发光提供有用的参考。