Piezochromic Behavior of 2,4,6-Triphenylpyrylium Tetrachloroferrate


Canasa P1, King D2, Cifligu P1, Llua Sanchez AF1, Chen SL2, Han H2, Malik T1, Billinghurst B2, Zhao J3, Park C4, George R. Rossman5, Pravica M1, Bhowmik PK4, Evlylukhin E1


1Department of Physics and Astronomy, University of Nevada Las Vegas, Las Vegas, NV 89154, USA
2Department of Chemistry and Biochemistry, University of Nevada Las Vegas, Las Vegas, NV 89154, USA
3Canadian Llight Source, Inc., University of Saskatchewan, Saskatoon, Saskatchewan S7N 2V3, Canada
4High Pressure Collaborative Access Team, X-ray Science Division, Argonne National Laboratory, Lemont, IL 60439, USA
5Division of Geological and Planetary Sciences, California Institute of Technoogy, Pasadena, CA 91125, USA

Abstract

In advanced photonics, there is a growing interest in piezochromic luminescent materials that exhibit multicolor switching, driven by their potential applications in optical recording, memory, and sensors. Here, the piezochromic behavior of 2,4,6-triphenylpyrylium tetrachloroferrate (Py-FeCl4) under high pressures from 0 to 9 GPa is reported. The observed multicolor changing properties of Py-FeCl4 (yellow–orange–red–maroon–black) are found to be fully reversible upon decompression to ambient conditions. The mechanism of Py-FeCl4 piezochromism is investigated via Raman, infrared, and UV–vis spectroscopy combined with powder X-ray Diffraction. The absence of structural phase transitions as well as the abrupt shifts of bandgap values together with characteristic Raman and IR peaks within 0-9 GPa suggests that the Py-FeCl4 multicoloring switching behavior is driven by an electron transfer between the inorganic FeCl4− anion and the organic pyrylium cation. The obtained results demonstrate that Py-FeCl4 dye is a good candidate for developing high-pressure sensing technologies designed to function in extreme environments. Moreover, due to the inherent role of molecular-structure relationships in the pyrylium salt's photophysical properties, findings suggest the potential discovery of piezochromic behavior in other pyrylium compounds.