Pressure-induced phase transitions in a new luminescent gold(<scp>i</scp>)–arylacetylide

Stimulus-responsive molecular materials are highly desirable because of the wide range of their potential applications. In particular, switching of physical properties opens application pathways for molecular materials as sensors or actuators. Property switching in solids can be achieved by inducing single-crystal-to-single-crystal (SCSC) phase transitions. Elucidating the mechanisms of such transformations and identifying the factors and (supra)molecular motifs that increase their probability is thus paramount to understanding property switching and materials design. Here, we present a new compound, (<i>p</i>-methoxy-phenylacetylide)(triethylphosphine)gold(I) (ArPEt), combining the photoluminescent core of gold(I) acetylide with triethylphosphine that should provide a rich conformational landscape and favor SCSC phase transitions due to low-energy interconversion pathways. We demonstrate its potential to undergo multiple pressure-induced SCSC transformations at ≈0.5 GPa and ≈2 GPa, the obtainable phases being dependent on the types of applied pressure-transmitting media. We describe structures of polymorphs of ArPEt and the mechanism of pressure-induced structural reorganizations based on very high-quality single-crystal X-ray diffraction data.