Pressure-dependent distinct luminescent evolutions of pyrene and TPA-Py single crystals

Aisen Li; Yan Liu; Changjiang Bi; Weiqing Xu; Zhiyong Ma; Haining Cui; Shuping Xu

doi:10.1016/j.saa.2020.118390

Pressure-dependent distinct luminescent evolutions of pyrene and TPA-Py single crystals

Spectrochim Acta A Mol Biomol Spectrosc. 2020 Aug 15:237:118390. doi: 10.1016/j.saa.2020.118390. Epub 2020 Apr 23.

Authors

Aisen Li¹, Yan Liu², Changjiang Bi³, Weiqing Xu³, Zhiyong Ma², Haining Cui⁴, Shuping Xu⁵

Affiliations

¹ College of Physics, Jilin University, Changchun 130012, PR China; State Key Laboratory of Supramolecular Structure and Materials, Institute of Theoretical Chemistry, College of Chemistry, Jilin University, Changchun 130012, PR China.
² Beijing State Key Laboratory of Organic-Inorganic Composites, College of Chemical Engineering, Beijing University of Chemical Technology, Beijing 100029, PR China.
³ State Key Laboratory of Supramolecular Structure and Materials, Institute of Theoretical Chemistry, College of Chemistry, Jilin University, Changchun 130012, PR China.
⁴ College of Physics, Jilin University, Changchun 130012, PR China. Electronic address: cuihn@jlu.edu.cn.
⁵ State Key Laboratory of Supramolecular Structure and Materials, Institute of Theoretical Chemistry, College of Chemistry, Jilin University, Changchun 130012, PR China. Electronic address: xusp@jlu.edu.cn.

PMID: 32361518
DOI: 10.1016/j.saa.2020.118390

Abstract

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.

Keywords: Excimer; Fluorescence; HLCT; High-pressure; Raman spectroscopy.